LARVAL TAXONOMY ANA BIONOMICS

OF

SOME BRITISH PIPUNCULIDAE

by

Forbes Peter Benton

A Thesis submitted for the Degree of Doctor of Philosophy,

University of London

Imperial College Field Station, Silwood Park, Sunninghill, Ascot, Berkshire. February, 1975• ABSTRACT

The thesis contains a taxonomic and ecological study of a family of insect parasites, the Pipunculidae (Diptera) which are

exclusively endoparasitic in Homoptera, Auchenorrhyncha. Little detailed biological information about them exists; this is surprising in view of their potential in the biological control

of leafhopper pests. The present studies extend the basic information on pipunculid biology and for the first time examine the taxonomy of the larvae.

Nearly half the total of 77 British species have been found at Silwood Park and 17 of these have been bred out. It was found that several species, particularly in the genus Eudorylas, could not be positively identified with the recently available key

(Coe, 1966). Drawings of the male genitalia of most species studied are included and these provide, almost exclusively, good absolute characters for species identification.

In studies of biology a Malaise trap was used to sample adult

Pipunculidae. Observations on the times of emergence of the larvae from the hosts, together with the analyses of the catches of adults in the Malaise trap, elucidated the life histories of the most common species.

Pipunculidae can vary considerably in size intraspecifically depending on the species of leafhopper host attacked. A large number of measurements were made in investigating this phenomenon and some relationships between overall variability and host specificity are suggested. The last part of the thesis contains descriptions of the larvae which were bred out. A key has been prepared for their identification up to generic, and in some instances up to the specific, level. Scanning electron micrographs have been included as an aid to illustrations of characters referred to in the key. Micrographs of the labial plates of the mature larvae of some species show probable sensory receptors which are believed to be hitherto undescribed in the Diptera. TABLE OF CONTENTS

• ?AM

INTRODUCTION 1

SECTION A

Methods of Rearing Pipunculidae 3

Duration of the Pupal Stage 4

Differences in the Pupal Duration between Species 6

Pupal Diapause 7

Effects of Hosts upon Insect Parasites 8

Range of Different Hosts attacked by Pipunculidae 12

The Variability of Adult Pipunculidae in relation to the Number of Different Host Species attacked 17

Other Factors causing Intrinsic Size Variation to vary with Species 28

Graphical Analysis of Polymodal Frequency Distributions 30

Summary and Discussion of Size Variation in Adult Pipunculidae 38

SECTION B' LIFE HISTORIES OF BRITISH PIPUNCULIDAE 62

SECTION C FIELD OBSERVATIONS ON THE OVIPOSITION BEHAVIOUR OF VERRALLIA SETOSA 77

SECTION D THE TAXONOMY OF PIPUNCULID LARVAE 79

Key to Mature Larvae and Puparia of Pipunculidae bred at Silwood Park 81

Detailed Descriptions of Larvae and Puparia 83

Sensory Receptors on the Labial Plates 87

SECTION E THE TAXONOMY OF ADULT PIPUNCULIDAE 117

Descriptions of some British Pipunculidae 119

DISCUSSION 163

SUMMARY 169 Page

•

ACKNOWLEDGMENTS 171

REFERENCES 172

APPENDIX A 174

APPENDIX B 176

APPENDIX C 178

Descriptions of Pipunculinae from Plattenhardt, W. Germany 179

• 1

INTRODUCTION

Pipunculidae are a family of Diptera which are exclusively

endoparasitic in auchenorrhynchous Homoptera. The little biological

information about them which is available comes from studies on

species parasitic on economically important leafhopper pests. This consists mainly of host records and percentages of parasitism. The

recent work of Waloff (1975) at Silwood Park, which is probably the

most detailed study to date, assesses the importance of Pipunculidae

as mortality factors. The present study was undertaken with a view

to extending the basic information on pipunculid biology and also to

examine the taxonomy of the larvae.

It was found in these investigations that some species,

particularly those of the genus ERioalsa could not be positively

identified with Coets key (1966). Descriptions and drawings of the

male genitalia of most species studied have been included in the

thesis. During 1974 a large collection of adult Pipunculidae was

made near Stuttgart in West Germany. This collection proved very

valuable for comparative work with the British species and further descriptions and drawings are given. Particular emphasis was again placed on the male genitalia. Nine new species are described (see Appendix C).

Whittaker (1969) used a Malaise trap to sample Verrallia aucta L, a parasite of the common cuckoo spit insect,in his studies at

Wytham Woods. Similarly, a Malaise trap was successfully used in the present study at Silwood Park. Data on the seasonal abundance of Pipunculidae were obtained. Several species were taken in sufficiently large numbers to elucidate voltinism. 2

It has been possible to show the extent to which the intra- specific variation in size of adult Pipunculidae is related to the number and sizes of the host species attacked. A large number of head width and wing length measurements were made in investigating this phenomenon and about a third of the thesis is devoted to this subject.

In the cyclorrhaphous Diptera the integument of the last larval instar becomes the puparial wall. The chitinised parts of the mature larva are therefore -left in or attached to the wall.

Examination of the puparia of bred Pipunculidae of known species is thus necessary in the study of larval taxonomy. Eighteen species were bred and drawingsand stereoscan electron micrographs of seventeen are given in Section D, together with a key for the identification of larvae and puparia to the generic level and in some instances up to the species. Probable sensory receptors are ••• described on the labial plates of some species. No previous electron microscope studies have been made of these receptors. 3

SECTION A

METHODS OF REARING PIPUNCULIDAE

Apart from the single breeding records scattered in the

literature and collected together by Coe (1966) the only other

biological work on Pipunculidae comes from economic studies such

as Williams (:x.957) on the sugar-cane Delphacidae and their natural

enemies in Mauritius and Esaki and Hashimoto (1936) on the leafhoppers

injurious to the rice plant and their natural enemies. Little

quantitative work is included in the economic studies apart from

the recording of percentages of parasitism. Probably the most

extensive ecological study of Pipunculidae is that of Waloff (1975)

at Silwood Park, where several species were bred out for the first

time. Descriptions of rearing methods were also included. During 3 the present study 18 species of Pipunculidae were bred out from 26

different species of leafhopper. The hosts represented a broad

coverage of the taxonomic groups of Auchenorrhyncha.

Methods

The most rewarding results were obtained by collecting parasitised

leafhoppers in the field with a sweep net and setting up the infected

hosts in tubes in the laboratory. Hosts containing mature larvae

are usually quite easy to recognise, at least in the male sex, because

the abdomens are greatly distended. As Perkins (1905, p.126) remarks,

the host's cuticle may become discoloured (usually to a paler colour).

Part of the overall effect of discolouration is due to the stretching

of the host's abdomen, revealing the intersegmental membranes, these

latter appearing white because the pale internal tissue becomes

visible through them. 4

The parasitised leafhoppers were placed individually, with a

small piece of food plant, into 3" x 1" glass tubes containing sand

to a depth of about The sand was kept moist to keep the humidity

up and the tubes were closed by a cork with a large central hole

covered with fine muslin to allow free circulation of air.

When the mature larvae emerged, which was invariably within

three days of collection, they pupated on or just below the surface of the sand. The two species Dorylomorpha haemorrhoidalis Zetterstedt

and Dorylomorpha xanthopus Thomson provide interesting exceptions in

that they pupated either on the wall of the glass tube or on the food

plant (see Section D). Emergence of the larvae took place in all

observations by rupturing of the host's integument at the junction of

the thorax and abdomen. It has already been established that only a

single pipunculid larva develops to maturity in the abdomen of the

host; e.g. Williams (1957, p.101) and Keilin and Thompson (1915, p.4).

This was also confirmed in the present study although shrivelled and

apparently encapsulated first instar larvae were occasionally found

together with a normal first instar larva in the same host.

Puparium formation was completed within forty-eight hours in

laboratory conditions. The duration of the pupal stage was about

two and a half weeks. Attempts to get field collected female

pipunculids to mate and parasitise leafhopper nymphs in the laboratory a were not successful.

DURATION OF THE PUPAL STAGE

Several bred Pipunculidae were kept in a 2000 constant temperature

room and the time in days was recorded from the beginning of puparium formation to the time of emergence of the imago from the puparium.

The data are summarised in Table 1. 5

TABLE 1 Duration in Days of the Pupal Stage at 200C

Mean Standard Standard Parasite No. Duration Deviation Error

Cephalops semifumosus Kowarz 5 15.30 0.67 0.29 C. semifumosusgv 5 13.50 1.12 0.50

Pipunculus campestris Latreille ? 5 14.80 0.57 0.25 P. campestris dv, 3 13.33 0.58 0.33

Eudorylas subterminalis Collin 6 17.75 0.42 0.17 E. subterminalis dicr 5 17.60 0.55 0.24

The above table shows that the duration of the pupal stage is greater in females than in males in all species. 't' tests were carried out to test for the significance of the difference between

sexes (Table 2(a)) and between species (Table 2(b)).

TABLE 2

SIGNIFICANCE OF THE DATA GIVEN IN TABLE 1

(a) Comparisons of the Pupal Duration between Sexes

F P t P C. semifumosus?? 2.778 0.2

P. campestris ?•? 1.025 0.5

E. subterminalis 0.515 E. subterminalis ape' 1.714 0.5KP 0.6

(b) Comparisons of the Pupal Duration between Species

Mean No. Duration *E. subterminalis 12 17.75 C. semifumosus 5 15.30 1.800 0.2

2E, subterminalis cA.? 12 17.75 1.30 0.5

C. semifumosus 5 15.30 P. campestris 5 14.80 1.385 0.5

The mean for E. subterminalis n - mean for E. subterminalis

Discussion

Commonly male insects emerge before the females and this is

probably partly due to the smaller size of many male insects requiring less time to develop (Chapman 1969 p.421 and Clements 1963). This is

biologically significant because the male will be on the wing earlier

than the female and, since the males are the more active partners in

mating, there is a possibility of more successful copulations if they

are already searching as the females emerge. That the pupal duration

is significantly less between the sexes in P. campestris and C. semifumosus is possibly a developmental adaptation that contributes to earlier male emergence.

• DIFFERENCES IN PUPAL DURATION BETWEEN SPECIES

The observed differences in pupal duration of E. subterminalis females

and C. semifumosus females (2.45 days) and of E. subterminalis females

and P. campestris females (2.95 days) at 20°C are highly significant

(P<0.001). The difference of 0.5 days in the developmental time between

P. aampestris females and C. semifumosus females is not significant (0.2

Some possible biological explanations for the shorter pupal durations in C. semifumosus and P. campestris are:

(a) that they are species which are adapted to more temperate

climates so they develop more rapidly at lower temperatures. It would be of value to have data of developmental times at

a series of temperatures so that developmental rates could

be compared;

(b) the duration of the pupal period is related to the number

of generations per year. One expects a multivoltine species

to complete its development more rapidly than a univoltine one.

There is some evidence that P. campestris is trivoltine

(Section B) although both C. semifumosus and E. subterminalis

are probably bivoltine.

PUPAL DIAPAUSE

The duration of pupal periods discussed above refers—to non- diapausing pupae. It has become evident through the work of Waloff

(1975) and in the present study that typically the British Pipunculidae overwinter in the pupal stage (Section B). When larvae that emerged and pupated from field collected leafhoppers did not produce adults after three to four weeks they were placed in an outdoor insectary to overwinter and re-examined in the following spring. The dates of adult emergence were recorded and these data are summarised in Section B.

In some instances attempts were made to break the diapause artificially by chilling the pupae in a refrigerator at 4°C for about five weeks and then placing them at 20°C. This technique met with some success and at least provided a more rapid means of identifying the parasites. 8

EFFECTS OF HOSTS UPON INSECT PARASITES

It is well known that different insect hosts can markedly affect the size of an insect parasite (e.g. Salt 1940). Salt worked with

Trichogramma and was able to show that, apart from the morphological effect of increased size of parasite with increasing host size, there are associated effects on the vigour, fecundity, longevity and rate of development of individuals of Trichogramma.

Bickel (1924) explained the dimorphism of a parasitic wasp

Dasymutilla bioculata Cresson (Hymen: Mutillidae) by showing that the frequency distribution of size was distinctly bimodal, the first mode representing specimens whose larvae were parasites of Microbembex monodonta Say and the second larger mode those whose larvae were parasites of the larger Bembix pruinosa Fox.

Effects of Different Hosts on Pipunculidae

The morphological effect of host size on that of the pipunculids is demonstrated and summarised in Tables 3 and 4; the data were obtained for four species bred at Silwood Park and the wing length and head width were used as indices of size.

The measurements were made using a graticule mounted in the eyepiece of a dissecting microscope. The wings were measured from the humeral cross-vein to the wing tip as indicated in fig 19.

The maximum width of the head was measured when viewed dorsally.

Only specimens preserved in 7O alcohol were used for these measurements.

In the tables the measurements are given in the original graticule units.,

The mean wing lengths in the tables vary considerably within a parasite species; e.g. male P. campestris bred from Euscelis obsoletus

Kirschbaum has a mean of 54.37 and the same parasite bred from Errastunus ocellaris Fallgn has a mean of 43.07. 9

TABLE 3

SIZE VARIATION IN FOUR SPECIES OF PIPUNCULIDAE BRED ON DIFFERENT HOSTS

Mean wing Standard Standard Host No. length Variance deviation error

Cephalops semifumosusAr

Conomelus anceps Germar (Adult) 27 41.74 3.362 1.833 0.350 C. anceps (V instar nymph) 9 38.61 2.439 1,561. 0.520 Megamelodes venosus Germar 2 35.75 Dicranotropis hamata Boheman (V instar nymphr 2 50.50

Cephalops semifumosus

C, anceps (Adult) 15 37.99 0.926 0.962 0.240 C. anceps (V instar nymph) 7 35.51 1.588 1.260 0.470 M. venosus 5 33.02 5.557 2.357 1.050 D. hamata (V instar nymph) 2 38.38

Pipunculus campestris J'J

Euscelis obsoletus Kirschbaum 7 54.37 6.849 2.617 0.980 Diplocolenus abdominalis Fabricius 6 48.08 6.021 2.453 1.000 Errastunus ocellaris Fallen 4 43.07 0.089 0.298 0.140 Euscelis incisus Kirschbaum 1 35.75 - -

Pipunculus campestris ??

E. obsoletus 2 58.05 Elymana sulphurella Zetterstedt 4 51.57 0.522 0.722 0.360 D. abdominalis 6 48.90 12.352 3.514 1.430 E. ocellaris .5 47.34 12.433 3.526 1.570

Alloneura sylvatica

E. ocellaris 7 30.38 0.394 0.628 0.230 1.324 D. abdominalis 6 32.75 1.755 0.540 Jassargus pseudocellaris Flor 6 28.23 0.818 0.904 0.360

Eudorylas subterminalis o'cr • E, ocellaris 48'd' 18 40.42 4.863 2.205 0.510 E. ocellarisW 9 40.45 4.732 2.175 0.720 E. ocellaris . 29 40.46 4.273 2.067 0.380 Psammotettix confinis Dahlbom crcr 5 38.02 0.207 0.454 0.200 P. confinis ?? 10 37.28 5.939 2.437 0.770 P. confinis c10'4 V? 15 37.52 4.007 2.001 0.510 J. pseudocellaris 7 38.71 0.488 0.698 0.260 D. abdominalis 8 40.27 3.179 1.783 0.630

•

10

Mean head Standard Standard Host No. width Variance deviation error Eudorylas subterminalis E. ocellaris 14 54.17 2.892 1.700 0.450 E. ocellaris gg 8 54.87 2.825 1.680 0.590

N.B. Means and standard deviations are in original graticule units. For wing lengths 12.65 units . 1 mm. For head widths 49.66 units . 1 mm.

TABLE 4 SIGNIFICANCE OF THE DIFFERENCE IN SIZE BETWEEN ADULT PIPUNCULIDAE BRED FROM DIFFERENT HOSTS

Mean wing Host length Cephalops semifumosusAP

C. anceps (Adult) 41.7438.61 1.378 0.5

C.anceps (Adult) 41.74 6.521 P<0.001 D.hamata (V instar nymph) 50.50

C. anceps (V instar nymph) 38.61 2.344 0.02

Cephalops ifumosus12_

C. anceps (Adult) 37.99 1.715 0.2

C. anceps (Adult) 37.99 0.001

C.anceps (Adult) 37.99 0.5

C.anceps (V instar nymph) 35.51 2.841 0.02

(continued as Appendix A) 11

To test the significance of the observed differences t tests were carried out. In comparisons where the variances of the two samples were assumed to be equal, from indications by the variance ratio test, the t was calculated as s- - t Si 1+ 1 na nb

Where the variances were not equal then the following quantity was calculated :-

(a - b) 1 t with d.f. is 2 s 2 u2 (1-u)2 na-4 n na nb b-1

Sa2/na

U rs q 4. S 2/n Sat/na b / b

In comparisons where less than five individuals were measured the two variances were assumed to be equal and the variance of the larger was used in the formula for t. The results of the tests with the values of F, t and levels of probability are presented in Table 4 (continued as Appendix A).

It is clear from this table that many of the size differences are highly significant. The production of different sized parasites can even occur within a single species of host, for example, in Conomelus anceps very significant differences in mean wing lengths of both male and female C. semifumosus depend on whether the parasites develop and emerge from adults or V instar nymphs. The sex of the host is apparently not a factor contributing to size difference, at least in the two species E. ocellaris and P. confinis that were examined. 12

No significant effects of host species on the size of pipunculids were seen in:-.

(a) E. subterminalis and females of P. campestris ex E. ocellaris and D. abdominalis (males of P. campestris differed

significantly although only four were measured ex E. ocellaris).

(b) Females of P. campestris ex E. sulphurella and D. abdominalis.

(c) Females of C. semifumosus ex adults of C. anceps and V instar nymphs of D. hamata (only two parasites measured).

(d) Males of E. subterminalis ex P. confinis and J. pseudocellaris.

The lack of any significant size difference here can of course be accounted for by similarity in the sizes of the hosts. Unlike

E. subterminalis and P. campestris (females), A. sylvatica Meigen showed a significant difference (P<0.01) from the two hosts E. ocellaris and D. abdominalis. This can be explained in terms of the overall size of the parasites, A. sylvatica being considerably smaller than

P. campestris and E. subterminalis. Any slight increase in host size might therefore produce a greater increase in parasite size.

RANGE OF DIFFERENT HOSTS ATTACKED BY PIPUNCULIDAE

Coe (1966) collated the breeding records of Pipunculidae up to

1966 with the genera of Pipunculidae recognised by both Coe and Collin.

In six out of the eight genera in which host records were available he suggested the following host specificity:-

Chalarus select Typhlocybinae (fam. Cicadellidae) Verrallia select Cercopidae Alloneura select Cicadellidae Pipunculus select Cicadellidae Cephalops select Delphacidae Eudorylas select Cicadellidae and Flatidae During the present study eighteen species of Pipunculidae were bred out at Silwood Park; four of these, Pipunculus fonsecai Coe, 13

P. zugmayeriae Kowarz, Dorylomorpha haemorrhoidalis Ztterstedt and Cephalops furcatus Egger for the first time. Many of the other species were bred out for the first time by Richards (Coe 1966) and

Waloff (1975). Claridge (person. commun.) bred out Verrallia setosa

Verrall and V. pilosa Zetterstedt for the first time. V. setosa was also bred out in the present study.

On the basis of these new records Coe's list may be modified as follows:-

Chalarus select Typhlocybinae (fam. Cicadellidae) Verrallia select Cercopidae and Macropsinae (fam.Cicadellida0 Alloneura select Cicadellidae Pipunculus select Cicadellidae Cephalops select Delphacidae and Cixiidae Eudorylas select Cicadellidae and Flatidae Dorylomorpha select Cicadellidae

More detailed data on the pipunculids and their hosts are given in Table 5 and among the more interesting breeding records are those of:-

(a) Cephalops furcatus from Cixius pilosus Olivier. This is

apparently the first record of Pipunculidae from this

family of Auchenorrhyncha.

(b) The two species of Dorylomorpha from Cicadellidae. There are

no previous host records of this genus.

(e) Verrallia setosa from Oncopsis flavicollis Linnaeus (first

record by M.P. Claridge (person. commun.)). Previously

Verrallia were thought to parasitise Cercopidae only.

Some Tentative Suggestions on the Evolution of Host Relations in Pipunculidae

Verrallia and Chalarus are among the more primitive genera of the

Pipunculidae, Aczel (1948). The relative size of the compound eyes 14

and the structure of the female ovipositor suggest this. It is

interesting that Verrallia (probably the most primitive genus) attacks

Cercopidae and Oncopsis in the subfamily Macropsinae of the Cicadellidae.

This possibly suggests a close affinity between the Cercopidae and this

group of the Cicadellidae. The Typhlocybinae being parasitised by

Chalarus can perhaps be regarded, together with the Macropsinae, as more

primitive Cicadellidae since the largest section (Deltocephalinae) are

parasitised by four genera of more recent Pipunculidae, i.e. Dorylomorpha,

Alloneura, Pipunculus and Eudorylas. The other main group of

Auchenorrhyncha, the Fulgoromorpha, seem to be attacked exclusively by the genus Cephalops. There is therefore good biological justification for this genus in addition to the diagnostic morphological features given in Coe's key, i.e. a coloured stigma on the wing, thorax with two dorso- central lines of hairs and a propleural fan of hairs. The larvae of

Cephalops are also generically distinct in having no obvious mandibular hooks or stylets (Section D).

Host Specificity

Looking at Table 5 one can see that generally there is not much host specificity as already shown by Waloff (1975). Single host records could fairly obviously be due to lack of data or (1) the parasite may be really host specific, or (2) only one of the parasite's range of potential hosts occurs at Silwood Park. A combination of the above reasons may be responsible for the particular form of Table 5. It is likely, however, that the following pipunculids are specific to one host in this part of their geographical range:-

(1) Pipunculus fonsecai on Doratura stal.ata, Boheman (2) Pipunculus zugmayeriae on Graphocraerus ventralis Fallen (3) Cephalops curtifrons Coe on Stenocranus minutus Fabricius 15 HOSTS Javesella discolor + Dicranotropis hamata + ±-f Conomelus anceps -I- + Laodelphax elegantulus ± Criomorphus williamsi -1- 1- Megamelodes venosus + Stenocranus minutus + iA

.I1-4H Cixius pilosus + H 0

Macros-tales sexnotatus + +

Eusceloid nymph A + Eusceloid nymph B -I- Euscelis plebejus + Euscelis obsoletus dr- +

D. Elymana sulphurella 4- + Cicadella quadrinotata + -I- E Graphocreerus ventralis + IDA Mocydia crocea -F

Arthaldeus pascuellus + i- + + CICADELL Diplocolenus abdominalis + + -I- + -I- E. Psammotettix confinis + + -I- + Jassargus pseudocellaris - -- -I I , Errastunus ocellaris i" 1- -F + -F +

Doratura stylata i-

Oncopsis flavicollis +

Neophilaenus lineatus + fhilaenus spumarius + 1 1

us

_

i

hop

t

tica eca lis uus m us

Host relations 5 - ta TA BLE e E-I lis

ida lva liq a tim M

1-4 xan us Pipunculidae studied ia uc fons of b l co us .r1 in os ha ho at Silwood Park. --1 a er es im sy o u

I-11, Cr3 CO s 4-3 CI-4 orp orr ay lus ip 44 co a) .4)4 lt aa •ri las ifum o u P, m o o 0 -P llia bterm lop bu 0 CO 0M m

eura Fi

a .t.% lom ug (1) CO 0 u r su haem unc fusc CO C.) CH 0 ha cH 0 dory z se . • • s • • Ver Dory Allot Eu Pip P. E. Cep C. C. 16

The reasons for these suggestions are as follows:-

(a) The three host species are taxonomically distinct and

do not have any other species in their respective

genera at Silwood Park.

(b) Very many hosts were dissected and mature larvae of

these pipunculids were not encountered in other hosts.

This applies in particular to Pipunculus zugmayeriae which has a very distinctive posterior spiracular plate

(see Section D) and is not likely to have been overlooked in other Cicadellidae if it were present.

(0 ) The host food plant of Stenocranus minutus, i.e. Dactylis glomerata (May 1971) grows in dense clumps and no other

delphacids have been seen to feed on this plant.

Cephalops furcatus (host record Cixius pilosus) and Verrallia setosa (host record Oncopsis flavicollis) may be grouped into one category regarding host specificity, i.e. pipunculids probably attacking host species belonging to one genus only. There are ten species of

Cixius in Britain (Le Quesne 1960). At least one other, namely

Cixius nervosus L. (Waloff 1973), occurs at Silwood Park. Oncopsis flavicollis is also one of many species in the genus Oncopsis. 17

THE VARIABILITY OF ADULT PIPUNCULIDAE IN RELATION TO THE NUMBER OP DIFFERENT HOST SPECIES ATTACKED

It has already been shown that highly significant size differences

are found in the adult pipunculids bred from different hosts. It

might therefore be expected that a pipunculid parasitising a wide range

of host species will be more variable than a pipunculid parasitising one itt or only a few. Evidence for this is provided in the form of a linear

regression analysis relating coefficients of variation of size of each

species with the number of host species attacked.

Methods

Measurements were taken of wing length and head width (in the way

described on page 8) to begin with, of the males of P. campestris,

A. sylvatica, Eudorylas obliquus Coe, E. obscurus Coe, E. fascipes

Zetterstedt and E. subterminalis. These pipunculids are parasitic on

Cicadellidae which were sampled in the grassland at Silwood Park with a

sweep net. Since there was no way of knowing,when a parasitised

leafhopper was swept, which species of pipunculid it contained, the

numbers of hosts recorded for each parasite (Table 5) can be taken as a

relative index of the numbers of host species in the parasiteb host

range.

The measurements used in calculating the coefficients of variation

were made only on those pipunculids which were taken in the Malaise

trap and in the standard hand netted samples in the years 1972 and S 1973 (Section B). An exception was Alloneura sylvatica. This species

is much more common than is suggested by the numbers taken in the

Malaise trap and in standard hand netted samples. The total for 1972

and 1973 being only 26 with a coefficient variation of 4.91437 (based

on wing length). A further 43 specimens were measured which were

collected by general sweeping; the coefficient of variation of these

was 4.83281. The difference between these two is negligible in 18

; comparison with the differences recorded between species in Table 6. The coefficient of variation of the combined 69 specimens was therefore used in plotting fig 1. The coefficients of variation for each species of pipunculid are given in Table 6.

Regression of Coefficient of Variation in Size on Number of Hosts Parasitised.

The relationship between the numbers of hosts parasitised and the corresponding coefficients of variation in size for the six species of Pipunculidae mentioned above which are parasitic on

Cicadellidae, is shown in fig. 1(a). The regression line and 95% confidence limits were plotted with the aid of a Linear Regression

Programme which also computes the regression equation and correlation coefficient. The regression coefficients were tested with 't' tests.

The statistical significance of the correlation coefficient (r) and 'F' tests were also carried out. The levels of significance are presented in Table 7.

In fig. 1(b) four further pipunculids are considered in the regression analysis, namely:

Cephalops semifumosus Cephalops furcatus Cephalops curtifrons Eudorylas zonellus

The following points should be noted however :-

(a) Cephalops is not a parasite of Cicadellidae (Table 5). (b) The coefficient of variation of C. curtifrons is based on

the wing lengths of 19 bred males. Only one adult male

was ever taken in the field. There is good reason to

believe that C. curtifrons is host specific (see above)

so it may be assumed that the coefficient of variation calculated from bred material would equal that calculated

from field collected adults.

19

The coefficient of variation of C. furcatus was based on

only seven specimens. The values for other species were

based on much larger numbers (Table 6). The individuals

measured were not from the standard samples.

(d) E. zonellus was not bred out. The distribution of its

wing length and head width measurements however (figs. 15

and 16) suggests that it may select two species or at

least two size groups of hosts. It has been assumed in plotting fig. 1(b) that it attacks two hosts.

In spite of the above the further four species added (fig. 1(b))

fit the trend so far demonstrated. In figs. 1(c) and 1(d) regression,

lines have been plotted in the same way as, in figs. 1(a) and 1(b) but

using coefficients of variation based on head width instead of wing

length. In figs. 1(c) and 1(d) E. subterminalis is not included

because the second brood of this species (Section B) were all mounted

on pins and not kept in alcohol like the rest. It was found that wing

length was not affected when specimens in alcohol were dried and

measured a second time as a check. But this did not apply to head

width. This is the species that does not give such a good fit in

figs. 1(a) and 1(b). Head width measurements were not made on the

other species present in figs. 1(a) and 1(b) but missing from figs. 1(c)

and 1(d).

- 20

TABLE 6

COEFFICIENTS OF VARIATION AND NUMBERS OF HOSTS PARASITISED IN MALE PIPUNCULIDAE

(a) Coefficient of variation based on wing length :

No. Parasite No. measured C.V. Hosts Parasitised P. campestris 59 9.97143 9 E. obliquus 49 5.59057 4 C. semifumosus 23 5.38140 6 A. sylvatica 69 4.99523 5 E. subterminalis 365 4.52946 5 E. obscurus 82 4.36353 3 E. zonellus 60 3.72103 2 E. fascipes 125 3.66618 2 C. curtifrons 19 3.62730 1 C. furcatus 7 1.66249 1

(b) Coefficient of variation based on head width :

No. Parasite No. measured C.V. Hosts Parasitised P. campestris 45 8.68268 9 A. sylvatica 58 5.57985 5 E. obliquus 39 5.55460 4 E. obscurus 55 4.37600 3 E. fascipes 123 3.81475 2 E. zonellus 52 3.56819 2

C.V. based on bred material • 21

TABLE 7

STATISTICAL SIGNIFICANCE OF REGRESSION LINES IN FIG.1

Reg. Eon. t F

1(a) y.0.872x+1.436 4.957 0.002

Statistical Tests to see if the Coefficients of Variation of the Adult Pipunculidae in Fig. 1 are siplificantly different

It is of value to know whether the coefficients of variation of each species are significantly different; in particular, those of the

species which are recorded as parasitising different numbers of hosts. Lewontin (1966) describes the following quick test for comparing coefficients of variations-

If two variables X and Y are really identical but Y is K times as large as X (the distribution of the Y values being exactly reproduced from the distribution of the X values by multiplying every X by K)

T. KX = mean of X S 2= Standard Deviation of X Ki S = Variance of X S2 .K 2S 2x

or Sy s KSx

When these relations hold C.V. . 100 x Standard Deviation Mean

Coeff. Var. Y 100 Sy = 122E2x 1222x = Coeff. Var. X KX Taking logarithms, if Y = KX then log I = log K + log X Log K is a constant and has no variance, thus 2 s2 and S S F glogY X log Y log X Fig. 1. Relationship between coefficient of variation and numbers of hosts parasitised for Pipunculidae

at Silwood Park. Coefficient of variation based

on wing length (1(a) and 1(b)) and head width

(1(c) and 1(d)).

.A C. furcatus B C curtifrons E. fascipes D E. zonellus E E. obscurus E. obliquus G E. subterminalis A. sylvatica C. semifumosus K P. campestris

2 2

12 Fig. la

4 5 6 7 8 9 10 I 1 'NUMBER OF HOST SPECIES PARASITISED COEFFICIENT OFVAR IATION NUMBER OFHOSTSPECIESPARASITISED 2 3 24

Fig.1c

0

8

7 ON I T IA VAR OF

6 ENT I FIC COEF

4

3 4 5 6 7 8 9 10 11 NUMBER OF HOST SPECIES PARASITISED 25

I0 Fig. Id

9

8

N 7 IO IAT R

VA 6

IENT OF 5 C

COEFFI 4

3

2

2 3 4 5 6 7 8 9 10 II NUMBER OF HOST SPECIES PARASITISED 26

Lewontin (loc. cit.) states, "the variance (or standard deviation)

of the logarithms of measurements gives a measure of intrinsic

variability which is invariant under a multiplicative change"

and "the advantage of the variance or standard deviation of the

logarithms over the coefficient of variation is that all the usual

statistical tests can be performed." To convert all my data to

logarithms would be time consuming. Lewontin points out that for

coefficients of variation less than 30% a close approximation is

that the variance of the logarithms (to the base e) is equal to the

square of the coefficient of variation. An 'F' test can be used

to compare the squared coefficients of variation. Since all the

coefficients of variation calculated in Table 6 are much less than

30% the 'F' test is applicable here. Different species are compared

in Table 8.

E. subterminalis gives a poor fit to the regression line in

figs. 1(a) and 1(b). Its coefficient of variation is significantly

smaller than that of E. obliquus (comparison 23, Table 8), whereas

the reverse is expected from the theory. In comparison 25 C. curtifrons

and C. furcatus give a significant difference at the 5% level. Only

seven specimens of C. furcatus were measured, however. The other

pipunculids recorded as parasitising equal numbers of hosts gave no

significant differences in their coefficients of variation (comparisons 22

and 24). Other comparisons where no significant differences were found

at the 5% level were 7, 8, 9, 12, 16. These anomalies are probably

accounted for by (a) low numbers measured and by (b) close similarity

in the numbers of hosts parasitised.

There is a source of bias in the records of the numbers of hosts, since the most abundant parasites are likely to be 'wed out more frequently. This may explain why E. subterminalis is recorded from 27

as many as five hosts. This species was by far the mDst abundant in the Malaise trap and hand netted samples. The large number measured (365)

is a consequence of this (Table 6). Had it been recorded from three hosts, it would have fitted better into the theory.

TABLE 8

COMPARISONS OF THE COEFFICIENTS OF VARIATION USED IN PLOTTING FIG. 1(b)

Species of Parasite C.V. (C.V)2 F P

P. campestris 1 9.97143 99.42942 3.433394 P<0.001 C. semifumosus 5.381404 28.95951

2 P. campestris 9.97143 99.42942 3.18129 P<0.001 E. obliques 5.59057 31.25447

P. campestris 3 9.97143 99.42942 P<0.001 A. sylvatica 4.99523 24.95232 3.98478

P campestris 9.97143 99.42942 5.22203 Pc0.001 4 E. obscurus 4.36353 19.04039

P. campestris 9.97143 P<0.001 5 E. fascipes 3.66618 ?:gg/I 23 7.39754

6 P. campestris 9.97143 99.42942 P<0,001 C, furcatus 1.66249 2.76387 35.97467

(continued as Appendix B) 28

OTHER FACTORS CAUSING INTRINSIC SIZE VARIATION TO VARY WITH SPECIES

Size Variation associated with Population Abundance

It is well known that animal populations vary in abundance. The

variation can be a cyclical one as in the lemmings of the Arctic Tundra with a period between peak populations of 3-4 years. Similar fluctuations in the predator numbers of the lemming, the Arctic fox,

have been associated with the population cycle of the lemming

(Myers & Krebs 1974).

Ford (1971) has shown how expanding populations become more

variable, there being relaxation of some selection pressure and

survival of atypical forms in the more favourable environments. In

the Marsh Fritillary Butterfly Melitaea aurinia studied by Ford, colour

pattern size and shape were characters which differed greatly from the

normal form during the period of rapid population increase 1920-24.

Before this the specimens were all very uniform.

The fluctuations in pdpulation density of an animal may not

necessarily be in phase in different parts of its range. If the

cycles can vary with locality in one species then fluctuations in

density could be out of phase with different species within one locality. The particular conditions favouring increase of species A at a given time in an environment may not be the ones favouring increase of species B. Accompanied with the numerical increase may

be increased variability. Such situations may exist in the species

of pipunculids considered in fig. 1. During the present study, therefore, some of the observed differences of variability between species (measured as coefficients of variation) may have been caused by unequal effects of environmental conditions. 29

Dissimilar Distributions of Hosts of Suitable Size

It can be supposed, partly on the basis of this study, that each parasite has an optimum size of host or hosts; the larger and smaller ones of the potential range being attacked progressively less frequently the further away they lie from the optimal size.

In other words, the size distribution of the parasites should be normal in localities where (a) a host or hosts are of very similar

Size, or (b) where there is a range of suitable hosts forming a size series of increments of approximately the same magnitude.

The difference between (a) and (b) should, of course, be apparent in the value of the coefficient of variation, (b) being greater than (a).

Mickel (1924) describes a situation where the parasite attacking two very different sized hosts gives rise to two very different sized groups of the parasite. In this situation the cumulative percentage size distribution gives a sigmoidal curve on arithmetical probability paper..

In figs. 2-16 cumulative percentages of wing length and of head width have been plotted on probability paper for pipunculids collected in large numbers (i.e. over 50). Only individuals taken from the Malaise trap and standard netted samples were measured. These individuals are thus identical to those used in calculations of coefficients of variation. Three species gave very good fits to normality, lt sylvaL.211, Chalarus spurius Fallen and P. campestris (figs. 8-12). The number of size classes and numbers contained within each class are next considered. In

P. campestris the former is very large and the latter very low (Table 12). The largest class, with six individuals, is 47.50-47.99 and the total number of classes equals 45. These figures refer to the wing length distribution. In spite of the generally low 30 numbers in each class both the wing length and head width distributions give good fits to normality (figs. 8 and 9), a straight line being a perfect normal distribution. In

E. subterminalis (figs. 2, 3 and 5) and, to a lesser extent in E. fascipes (figs. 6 and 7), the points deviate considerably from a straight line. The numbers in the distributions, 365

E. subterminalis and 130 E. fascipes, are sufficiently large to attempt a graphical analysis, as described below, which attempts to explain these deviations.

GRAPHICAL ANALYSIS OF POLYMODAL FRE. UENCY DISTRIBUTIONS

Using probability paper Harding (1949) describes how bi and polymodal distributions may be analysed. E. fascipes and

E. subterminalis botli have distributions which appear to comprise a number of different populations with fairly distinct points of inflexion and analyses of these have therefore been undertaken.

Separation of Cumulative Percentage Wing Length Distribution of 130 E. fascipes males into Two Component Populations

Fig. 6 indicates a point of inflexion at about 40%. This inflexion is more evident in the head width distribution (fig. 7).

For the present purposes the upper part of the distribution in fig. 7, i.e. size class 66.00-66.49 onwards, can be ignored, since it is represented by only two individuals out of the total of 123 (Table 10).

The point of inflexion, therefore, is taken as separating the probability distribution into two parts, corresponding to 40% and

60% of the total. The two straight lines of fig. 6 were obtained 100 by scaling up the 40% and 60% parts in the proportions and 160 respectively. The sigmoidal curve indicated by circles in fig. 6 is the resultant of the latter two straight lines expressed as cumulative percentages. The crosses are the cumulative percentages 31

plotted from the actual data. The goodness of fit test can

be applied to see how well this analysis fits the original data.

The expected frequencies were calculated using probit tables,

the means and standard deviations being read off from the probability

paper. Expected frequencies were also calculated directly from the

straight lines in the fig. 6 analysis. Table 9 shows that the two

expected frequencies are in almost perfect agreement. The more a direct method can therefore be used in goodness of fit tests. a In the calculation of X the numbers in the tails of the distribution

have been added together in accordance with the rule that no

expectations should be less than 5 units. As Harding explains,

a degree of freedom is subtracted for each mean, for each standard

deviation, for all but one of the component populations and for the

total. In the case of Table 9 this leaves 6 degrees of freedom.

The analysis of fig. 6 gives the solution:-

40% of the population with mean of 40.64 and S:.=D. 1.613 60 of the population with mean of 42.40 and S.D. 1.325 a The value of X 6.676 in Table 9 was obtained by comparing

the observed with the expected frequencies; the latter were

calculated from probit tables. A X value of 6.430 with 6 d.f. and 0.5>P>0.3 was obtained when comparing with the expected frequencies

calculated directly from the 40% and 60% lines. The analysis of

fig. 6 is certainly not the only or necessarily even the best solution. • When the 60% line was drawn in a slightly different position such that a its mean was 42.58 and S.D. 1.263, the value of was 7.742 with

0.3>P>0.2. This fit was not so good but was still a possible one.

Assuming there are in reality two populations approximately in

proportions of 40% and 60%, then the feasible solutions will have

their means of about 40.64 and 42.40. The biological meaning behind 32

the two normal distributions is that there is one or a group of similarly sized hosts comprising 40% of the host range of E. fascipes which produce adult flies (males) with mean wing length near to

40.64 units and S.D. 1.613. Similarly, the remaining 60% of hosts produce parasites of mean wing length 42.40 and S.D. 1.325.

Errastunus ocellaris and Elymana sulphurella were found to be parasitised by E. fascipes and there is some evidence that

E. sulphurella may be the major host at Silwood Park.

(a) Both E. sulphurella and E. fascipes are univoltine

(Waloff and Solomon 1973) and both species occur at

a time of year between the broods of the common bivoltine

cicadellids and other Eudorylas species.

(b) Out of the total nine E. fascipes bred out, seven

were from E. sulphurella and two from E. ocellaris.

Much larger numbers of E. subterminalis, E. obscurus

and E. obliquus were bred out yet none was from

E. sulphurella.

Unfortunately, only three male E. fascipes were bred _out so it was not possible to compare the wing lengths with the analysis in fig. 6. From E. ocellaris 29 male E. subterminalis were bred

(Table 3) so in the analysis below a direct comparison could be made.

Operation of Cumulative Percentage Wing Length Distribution of 365 E. subterminalis males into Three Component Populations

In figs. 2, 3 and 5 the wing length and head width distributions of E. subterminalis have been plotted. A distinct point of inflexion is seen at 20% in fig. 5 and at about 40% in fig. 2. From these percentages upwards the points fall on almost perfect straight lines.

33

A less obvious point of inflexion occurs at about 5/0 in both figures.

The lower points in both figures deviate considerably from the

extension of a straight line that could be drawn through the upper

parts of the distributions. Inspection of the frequency classes

of fig. 2 in Table 11 shows that the bulk of the observations lie in

the upper sector corresponding to the upper part of the distribution

(fig. 2).

Continuing the analysis in the same way as with E. fascipes the

following result is obtained for E. subterminalis s-

5.75V, of the population with mean 40.23, S.D. = 1.925 and C.V. = 4.785 33.425% " " It " " 43.87, S.D. . 1.793 and C.V. = 4.087 60.822% " " " " 45.70, S.D. = 1.33 and C.V. = 2.910

If the 5.753% and 33.425% parts are considered as one, i.e. 39.178% so that there are now two components to the whole distribution, the

goodness of fit gives 0.30>P>0.20 for 10 degrees of freedom. The

fit is therefore not as good as that of fig. 2 where the value of P is 0.5>P>0.5 (Table 11). There is another more important biological

advantage of the solution depicted in fig. 2. Tables 3 and 4 contain the mean wing lengths and head widths of male E. subterminalis bred

from various hosts. The mean wing length for D. abdominalis was 40.27 and for E. ocellaris 40.46. These sizes are very close to the 5.753% component of fig. 2. Comparison of bred flies with this compbnent

gives values of t = 0.05, P>0.9 for D. abdominalis and t = 1.121,

0 0.1>P>0.05 for E. ocellaris. An 'F' test to compare the close approximation of the variance of the logs of the measurements (i.e. squared coefficients of variation) for E. ocellaris and the 5.753%

component shows them to be very similar (P>0.5). The size of the

bred flies is significantly different from that in the other two

components of fig. 2 (i.e. 33.425% and 60.822%). The 't' testa

having the value of P<0.001 for both. 34

It can therefore be concluded that about 5.75% of E. subterminalis were parasitising D. abdominalis, E. ocellaris and other unknown hosts

producing parasites of similar size. This applies to the 1972-3

samples. There are, however, a number of criticisms to this conclusion :-

(1) The other three hosts known to be parasitised by

E. subterminalis, i.e. P. confinis, J. pseudocellaris and

A, pascuellus (Table 5), produced even smaller sized flies than those ex E. ocellaris and D. abdominalis (Tables 3 and 4). These are not accounted for in the fig. 2 solution.

If the wing length distributions are analysed separately for

1972 and 1973 (fig. 4 and below) the 1972 solution gives a 5.051% component with mean of 38.80 and standard deviation of 1.375. This is very near to the size of E. subterminalis

males (38.71) bred from J. pseudocellaris .(Table 3). Prom

P. confinis the size was 37.52 which is not significantly

different from 38.71 (Table 4). The latter two hosts,

like D. abdominalis and E. ocellaris can thus be associated

with only a small component of the total hosts of E. subterminalis.

(2) It can be argued that the distribution in fig. 2 is not the

result of overlapping normal distributions but a consequence

of wing length being a poor index of size. Three reasons

can be given against this criticism s-

(a) The distribution of head width frequency (fig. 5)

follows very closely on the wing length frequency

in this species as well as in the other species

(figs. 2-16). Only the head widths of the first

brood are plotted for E. subterminalis because of

the reasons given on page 19. 35

(b) The wing length distributions of E. subterminalis

for 1972 and 1973 (fig. 4) have a similar

appearance. One cannot expect them to be

identical since the species composition and

relative numbers of potential hosts of E. subterminalis presumably vary from year

year.

(0) Measurements of Az sylvatica and of P. camnestris both approximate to a normal distribution.

Only 64 P. camnestris were measured for wing

length and there are a large number of size

classes (45) (Table 12), so the deviations from

the straight line (fig. 8) are to be expected.

That measurements of these species are good

fits to normality suggests that their host

ranges at Silwood Park form a continuous size

series. If wing length is a good index of size

in these two species it can be assumed to be a

good index in E. subterminalis without the

necessity of having to transform the data in

order to make it a better fit to a single normal

distribution. It is relevant to add here that

wing length and head width are very highly

correlated as illustrated for E. zonellus (fig. 17)

and summarised in the form of regression equations

and significance tests for the other species

(Table 13).

(3) Lastly, probably the most valid criticism is that the bred

specimens of E. subterminalis are dwarfed and the mean wing

lengths given in Table 3 cannot be taken as the mean wing 36

lengths that would be produced under field conditions.

However, it may be recalled that most of the larval

development was in fact under field conditions; only

leafhoppers with well developed larvae were collected.

These larvae invariably emerged within three days. Only

the pupal stage was not spent under field conditions.

Even this only applies to the first generation of

E. subterminalis. The diapausing pupae of the second

generation were kept in an outdoor insectary in conditions

approximating to those in the field.

Pig. 3 depicts the cumulative percentage of wing length distributions of the 29 E. subterminalis males bred from E. ocellaris at Silwood Park and a sample of 63 males of the same species collected in Plattenhardt (near Stuttgart, West Germany) during

July and August, 1974. The two distributions are very similar.

A Mann-Whitney U-test for the two samples gives a value of P = 0.755.

The following may be deduced from figs. 2 and 3 :-

(1) The principal host or hosts of E. subterminalis in the

locality near Stuttgart are of the same size as E. ocellaris.

(2) The disparity between the wing length distributions from

Plattenhardt, Test Germany (fig. 3) and Silwood Park

(fig. 2) is explicable in terms of the sizes and

availability of suitable hosts.

The change in wing length distribution with locality reflects the capacity of the parasite to utilise a variety of hosts. The extent to which this happens gives some measure of the range of host specificity. 37

Separation of Cumulative Percentage Wing Distributions of E. subterminalis Males collected in 1972 and 1973

Fig. 4 shows the two distributions. They show the same general pattern, although they are not identical, for the reasons already suggested. Using the same graphical methods as before, the separation of the 1972 distribution gives :-

5.051% of the population with mean 38.80, S.D. 1.375 and C.V. 3.544 25.252% of the population with mean 42.00, S.D. 1.100 and C.V. 2.619 69.697% of the population with mean 44.70, S.D. 1.490 and C.V. 3.333 0.30>P>0.20 x rR 4.960, d.f. = 4, and for 1973 :-

4.135% of the population with mean 40.75, S.D. 2.055 and C.V. 5.043 , 18.421% of the population with mean 43.60, S.D. 1.660 and C.V. 3.807 77.444% of the population with mean 45.65, S.D. 1.290 and C.V. 2.826

8.359, d.f. . 6, 0.30>P>0.20

As in the fig. 2 solution, these analyses again suggest that the majority of E. subterminalis (about 70% for 1972) are parasitising a considerably larger host or hosts of similar size than have so far been found. In all E. subterminalis size distributions (figs. 2, 4 and 5) approximately the upper 60% component follows very closely a straight line. As already shown for the fig. 2 analysis, this upper component is significantly different from the size distribution of the largest bred flies (ex E. ocellaris (fig. 3 and Table 3), with mean wing length of 40.46 units (P<0.001).

Cumulative Percentao.e Size Distributions of E. zonellus, E. obliques. P. campestris and b. sylvatica

There were not enough measured individuals available of these species to attempt the above analyses. However, the following points are of interest 38

A. sylvatica and P. campestris. Measurements of these two species

give very good fits to normal distributions (figs. 8, 9, 11 and 12).

This indicates that hosts around the optimum size are available and

the abundance of them above and below the optimum is similar.

E. zonellus. In this species there are similar points of inflexion

for both wing length and head width (figs. 15 and 16), indicating two

size groups of hosts. For this reason it was assumed in constructing

Table 6 that two species of hosts were parasitised.

E. obscurus and E. obliquus (figs. 13 and 14). The distributions resemble those of E. subterminalis but no attempt was made to split

them up as the data are insufficient.

SUMMARY AND DISCUSSION OF SIZE VARIATION IN ADULT PIPUNCULIDATI

It has been shown that in four different genera of Pipunculidae

the mean sizes of flies bred from different leafhopper species can

vary considerably. The variation is due simply to the difference

in size and hence availability of food for the parasitic larvae within

different hosts. This phenomenon is well known in other insect

parasites (Salt 1940).

Parasites that are highly specific may be expected to be much

less variable in size than those that attack a wide range of hosts.

Those pipunculids that accept several host species encounter greater

variations in host size and hence are more variable in size themselves.

Evidence of this in Pipunculidae is provided in the form of regression

analyses correlating number of host species of the parasites with coefficient of variation in size. There is a source of bias in the

numbers of hosts recorded. The most common pipunculids will tend to

be bred out more frequently and be recorded from a disproportionately larger number of hosts. Curiously, the species with the worst fit to 39

the regression lines in figs. 1(a) and 1(b) is the mast abundant one

at Silwood Park. For a better fit it would have to be bred from

three hosts instead of five. The regression lines of fig. 1 are

nevertheless highly significant and the coefficient of variation may

be used as a relative index of the degree of host specificity. Such

a situation may well be found in other groups of insect parasites.

Not all the variation in adult size can be explained by numbers

of host species parasitised. Fig. 1(b) gives sums of squares due to

the regression as 34.590 and sums of squares due to residuals as 7.057.

Apart from errors in technique, some of the variation could be caused

by increase in variability associated with parasite abundance (p.28)

or to dissimilar distributions of hosts of suitable size (p.29).

The distributions of cumulative percentage wing length and head

width of different Pipunculidae were shown to differ from one another

(figs. 2-16). Apart from differences in means and in coefficients of

variation, the more precise forms of the distributions vary. Some

approach very closely to normal distributions, e.g. A. sylvatica and

•P. campestris, suggesting that their hosts form a continuous size series.

Other species like E. zonellus show a distinct bimodal distribution,

suggesting a large discontinuity separating the host range into two

size groups. Yet others, like E. subterminalis and E. fascipes, are

intermediate between the first two conditions. Different host sizes

give rise to overlapping normal distributions which, however, are not

sufficiently distinct to yield modes (as in E. zonellus), and yet the

distributions deviate from normality. An attempt has been made with

E. subterminalis to fit normal distributions to the observed frequency

distribution and to link these fitted normals with the sizes of parasites

produced by known hosts. The results strongly indicate that the

majority of E. subterminalis are parasitising some considerably larger 40

cicadellid host than is known so far. Of the knowirhosts D. abdominalis and E. ocellaris give rise to the largest flies;

according to the fig. 2 analysis these two hosts, together with

any other unknown hosts producing parasites of the same size (i.e.

with mean wing length equal to or not significantly different from

40.23 units), constitute only 5.753% of the known hosts parasitised

by E. subterminalis. The most common hosts of this widespread

species of Pipunculidae are thus still unknown.

• 41

5.75% 33.43% 60.82%

35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 Wing Length Fig. 2. Cumulative percentage wing length distribution of 365 E. eubterminalis males with a:Possible separation into three populations. . points plotted from actual data 0 resultant of 5.75%, 33.435 and 60.e2% component distributions

42

00 +

0

0 0

+ 0 0 4- O

9

'J1 + 000

+

33 34 35 36 37 38 39 40 41 42 43 44 Wing Length

Fig. 3. - Cumulative percentage wing length distributions of E. subterminalis males. 0 29 specimens bred from E. ocellaris at Silwood Park 63 specimens collected near Stuttgart, W. Germany ▪

„ tr1

"44 0 cti 0 0 0 + 0 0 0 0 [14 C) 0 0

0 cti • ri

a' a)

+ 0 a) c: + 0 CY. O •r4 r- 0 0 • H 0.) 0 1 i •H 0 V. + -40 cdC 0 r Ti + 0 0 0 • 4- • 410 •H

W.+ CO

•

I I I I 1 1 1 1 99.99 99.9 99.8 99 90 95 90 80 70 60 50 40 30 _ 20 10 5 2 1 0.5 0.2 0.1 0.05 0.01 Cumulative Frequency

44 VJ C0 (.0

O CD

4.0 O 0

CD 0 0

CI 0

Cr 0 0 n0 C 3 c 0 ca 0

O 0 =CD o ° 0 0 ■O11. 0 0 O ° 0 0 0

asi 0 0

000

O 1 O 49 50 51 52 53 54 55 56 57 58 59 60 61 Head Width

Fig. 5. - Cumulative percentage head width distribution of 238 first brood E. subterminalis males.

45

0 3 ET

CD -n CD

CD

36 37 38 39 40 41 42 43 44 .45 46 Wing Length Fig. 6. - Cumulative percentage wing length distribution 'of 130 E. fascipes males with a possible separation into two populations. + points plotted from actual data 0 resultant of 40YA and 60 component distributions 46

0 0 0 0 0 0 0 0 0

0 0

0 0

I.'

00

I I I I I 55 56 57 58 59 60 61 62 63 64 65 66 67 6S 69 Head Width

Fig. 7. - Cumulative percentage head width distribution of 1 123 E. fascipes males. 47

4

4

4

=

CO 4

O

co

co

I t 1 l t 1 t I 1 it 99.99 99.9 99.8 99 98 95 90 80 70 60 50 40 30 20 10 5 2 1 0.5 0.2 0.1 0.05 0.01 Cumulative Frequency

Fig. 8. - Cumulative percentage wing length distribution of 64 P. campestris males. 48,

t.0

c.

11

Ll

O

0 O 3 O C

Cnt

CD

o r C

C)

r

•

I 50 52 54 56 58 60 62 64 66 d8 70 - 72 74 76 78 Head Width

Fig. 9. - Cumulative percentage head width distribution of 53 P. campestris males. 49

27 28 29 30 31 32 33 34 Wing Length

Fig. 10. - Cumulative percentage wing length distribution of 62 C. spurius males. co

0 C.

3 m

co O

Ca "L.

CD

1•3 O

O

O O Gil

30 31 32 33 34 35 36 37 38 Wing Length

Fig. 11. - Cumulative percentage wing length distribution of 69 A. sylvatica 51

•(C

cc

C,

C 3 a 7c;

CD -fl "CD

CD

4•C

14

I I I 43 44 45 4G 47 48 49 50 51. 52 53 54 55 Head Width

Fig. 12. - Cumulative percentage head width distribution of 58 A. sylvatica males. 52

0

0 0

0

0 0 0 0

0 0 0 0 0 0 0

0

O O GT

—a 40 41 42 43 44 45 46 47 48

Wing Length

Fig. 13. - Cumulative percentage wing length distribution of 82 E. obscurus males. 53

Cr)

O

+

I 1 1. 1 o 1 I I E I 1 I 1 I I 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 Wing Length

Fig. 14. - Cumulative percentage ring length distribution of 49 E. obliquus males. 54

0

0

0 0

0 0

0 0 0 0 0 0 00

0 0 0 0

52 53 54 55 56 57 58 59 60 61 62 Wing Length

Fig. 15. - Cumulative percentage wing length distribution of 67 E. zonellus males. 55

0 0

0 0 0 0

0 0

= 11 1 1 [ 1 1 68 69 70 71 72 73 74 75 76 77 78 79 Head Width

Fig. 16. - Cumulative percentage head width distribution of 52 E. zonellus males. Fig. 17. Regression line of head width on wing length for Eudorylas zonellus. 56

84

82

80

• 66

54 55 56 57 58 59 60 61 62 63 WING LENGTH 57

TABLE 2

ANALYSIS OF WING LENGTH DISTRIBUTION OF 130 E. FASCIPES 0,70071

Wing Length Observed Frequency Calculated Class Frequency From Fig. 6 40% 60% Total Mean=40.64 Mean.42.40 S.D..1.613 S.D..l.325 Cale. Cale. Calc. Calc. Cale. Cale. From From From From From From 40% Line Probit 60% Line Probit 40%&60% Probit Tables Tables Lines Tables 36.50-36.99 1 1 0 0 0 1 0 37.00-37.49 0 1 1 0 0 1 1 37.50-37.99 2 1 1 0 0 1 1 38.00-38.49 1 2 2 0 0 2 2 38,50-38.99 4 3 3 1 0 4 4 39.00-39.49 4 4 4 1 1 5 5 39.50-39.99 6 5 6 2 2 7 8 40.00-40.49 11 6 6 3 3 9 9 40.50-40.99 8 7 6 5 5 12 12 41.00-41.49 15 6 6 8 8 14 14 41.50-41.99 20 5 5 10 10 15 15 42.00-42.49 16 4 4 12 12 16 16 42.50-42.99 18 3 3 11 11 14 14 43.00-43.49 8 2 2 9 10 11 11 43.50-43.99 6 1 1 7 7 8 8 44.00-44.49 6 1 1 4 5 5 5 44.50-44.99 3 0 0 3 3 3 3 45.00-45.49 0 0 0 1 1 1 1 45.50-45.99 1 0 0 1 1 1 1 Total 130 52 51 78 79 150 130

a = 6.676, d.f. . 6, 0.5>P>0.5

0 58

TABLE 10

HEAD WIDTH DISTRIBUTION OF 123 E. FASCIPES

Head Width Observed Class Frequency 54.50-54.99 1 55.00-55.49 0 55.50-55.99 2 56.00-56.49 0 56.50-56.99 4 57.00-57.49 3 57.50-57.99 1 58.00-58.49 3 58.50-58.99 5 59.00-59.49 9 59.50-59.99 5 60.00-60.49 5 60.50-60.99 10 61.0o-61.49 14 61.50-61.99 13 62.00-62.49 15 62.50-62.99 9 63.00-63.49 4 63.50-63.99 9 64.00-64.49 4 64.50-64.99 3 65.00-65.49 1 65.50-65.99 1 66.0o-66.49 0 66.50-66.99 0 67.00-67.49 0 67.50-67.99 1 68.00-68.49 0 68.50-68.99 1

Total 123

• 59

TABLE 11 4p

ANALYSIS OF WING LENGTH DISTRIBUTION OF 365 E. SUBTERMINALIS ec?,

Frequency Calculated nag...1021E1h Observed Class From Fig. 2 5.753% 33.425% 60.822% Total Mean.40.23 Mean=43.87 Mean=45.70 S.D..1.925 S.D..1.793 8.D..1.330

36.50-36.99 1 1 0 0 1 37.00-37.49 1 1 0 0 1 37.50-37.99 0 1 0 0 1 38.00-38.49 2 1 0 0 1 38.50-38.99 1 2 0 0 2 39.00-39.49 3 2 0 0 2 39.50-39.99 1 2 2 0 4 40.00-40.49 3 2 2 0 4 40.50-40.99 9 2 3 0 6 41.00-41.49 5 2 6 0 6 41.50-41.99 11 2 7 1 9 42.00-42.49 9 1 10 1 12 42.50-42.99 16 1 11 3 15 43.00-43.49 21 1 12 6 19 43.50-43.99 31 0 13 11 25 44.00-44.49 29 0 13 18 31 44.50-44.99 37 0 12 27 38 45.00-45.49 49 0 lo 31 42 45.50-45.99 40 0 8 31 39 46.00-46.49 32 0 5 31 36 46.50-46.99 27 0 4 25 30 47.00-47.49 20 0 2 17 19 47.50-47.99 6 0 1 10 11 48.00-48.49 5 0 I 6 7 48.50-48.99 5 0 0 3 3 49.00-49.49 0 0 0 1 1 49.50-49.99 1 0 0 0 0

Total 365 21 122 222 365

• A,. 7.541, d.f. = 7, 0.5>P>0.3 6o

TABLE 12

WING LENGTH AND HEAD WIDTH DISTRIBUTIONS OF P. CAMPESTRIS 0/16A

Wing Length Observed Head Width Observed Class Frequency Class Frequency 37.50-37.99 1 52.00-52.99 1 38.00-38.49 53.00-53.99 38.50-38.99 54.00-54.99 39.00-39.49 55,00-55.99 39.50-39.99 56.00-56.99 2 40.00-40.49 57.00-57.99 3 40.50-40.99 58.00-58.99 4 41.00-41.49 1 59.00-59.99 3 41.50-41.99 1 60.00-60.99 1 42.00-42.49 1 61.00-61.99 4 42.50-42.99 3 62.00-62.99 5 43.00-43.49 1 63.00-63.99 1 43.50-43.99 64.00-64.99 4 44.00-44.49 2 65.00-65.99 3 44.50-44.99 4 66.00-66.99 2 45.00-45.49 1 67.00-67.99 2 45.50-45.99 68.00-68.99 2 46.00-46.49 4 69.00-69.99 4 46.50-46.99 2 70.00-70.99 3 47.00-47.49 4 71.00-71.99 3 47.50-47.99 6 72.00-72.99 1 48.00-48.49 73.00-73.99 2 48.50-48.99 74.00-74.99 1 49.00-49.49 2 75.00-75.99 49.50-49.99 2 76.00-76.99 2 50.00-50.49 3 50.50-50.99 2 51.00-51.49 4 Total 53 51.50-51.99 52.00-52.49 3 52.50-52.99 1 53.00-53.49 53.50-53.99 2 54.00-54.49 2 54.50-54.99 2 55.00-55.49 2 55.50-55.99 56.0o-56.49 1 56.50-56.99 1 57.00-57.49 57.50-57.99 58.00-58.49 3 58.50-58.99 59.00-59.49 59.50-59.99 3

Total 64 61

TOME 13

REGRESSION LINES OP HEAD WIDTH ON WING LENGTH FOR ADULT PIPUNCULIDAE •

Parasite Regression Eqn.

E. zonellus y = 1.166x + 6.496 12.616 P<0.001 E. fascipes y = 1.222x + 10.608 9.257 P<0.001 E. subterminalis y . 0.667x + 26.778 22.010 P<0.001 E, obscurus y . 1.156x + 8.974 8.543 P<0.001 E. oblicuus y = 1.458x - 4.530 11,745 P<0.001 62

SECTION B

LIFE HISTORIES OF BRITISH PIPUNCULIDAE

Outline life cycles of three British pipunculid species have

been given by (a) Rothschild (1964) for C. semifumosus,

(b) Whittaker (1969) for V. aucta and (c) May (1971) for

C. curtifrone. Somewhat more detailed descriptions of the

phenologies of some Silwood Park Pipunculidae are given by Waloff

(1975). None of the above workers, however, sampled the adults

and larvae of Pipunculidae regularly and extensively. The

phenologies of 11 species are described in detail below based on

data from regular field sampling.

Malaise Trap. A Malaise trap was used to sample the adults. A

drawing of this trap is given in fig. 18. This particular trap is

9i feet in height and is based on a design illustrated by Chanter (1965).

It consists of a wooden frame covered with fine white terylene netting.

The top of the pyramid shaped portion is made of perspex and attached

to the latter is a Kilner jar containing water with a few drops of

Tee-pol. The latter reduces the surface tension so that insects

dropping downwards will more readily penetrate the surface film and

drown. It was found convenient to empty the Kilner jar every three days; decomposition of the catch resulted when it was left for longer.

The trap was placed in a position adjacent to a bramble patch. This site was chosen deliberately because it was known from preliminary field observations that the bases of bramble hedgerows were favourite haunts of many Pipunculidae.

The total number of Pipunculidae taken in the Malaise trap was over 200 for 1972 and over 300 for 1973. Malaise trapping was not started until 20th June in 1972. This is indicated in histograms 63

(figs. 20-32). The annual catch of Pipunculidae in.the Rothamsted suction trap at Silwood Park was seldom more than thirty specimens.

A second sampling method was used to supplement and act as a check on the Malaise trap data. This involved simply a hand-held insect net. Throughout 1972 and 1973, from the beginning of May until mid-October (the precise times are indicated on the histograms, figs. 20-32), regular samples of Pipunculidae were taken at a site near Silwood Park lake. All Pipunculidae seen in an hour long period flying along a particular stretch of hedgerow were collected with a net. These samples were standardised as far as possible by selecting a sampling period between 4 and 5 p.m. and by only collecting on warm calm days. The samples were taken as regularly as they could be. This generally meant once each week but, of course, good collecting conditions did not always occur regularly. Apart from a three and a half week gap in the collecting record during 1972 between mid-May and the first week of June (as indicated in the histograms), the maximum gap between two successive samples was ten days. The minimum number of flies taken by this method was 7 and the maximum 42.

The results of the Malaise trap and insect net samples are expressed in figs. 20-32 in the form of histograms. The agreement between the two methods is very good, in particular for the more common species.

Larval Emergence Dates

During 1972 the leafhopper fauna at Silwood Park (in particular the grassland fauna) was regularly sampled from mid-April until mid-

November. (These dates are indicated in histograms, figs. 20-32).

Leafhoppers parasitised by the Pipunculidae collected were set up in the way described under rearing methods. The dates when the larvae emerged from their hosts were recorded and the data have been summarised in the histograms. Although samples were not taken in a strictly quantitative way, sampling was regular throughout the 64

above-mentioned period. For this reason the difference in magnitude

of the larval broods seen in some histograms, e.g. of E. obliquus, may

be an artifact due to the inadvertent differences in the intensity of

the sampling effort. Significance can be justifiably attached,

nevertheless, to the times of year of the emerging larvae. This is

well illustrated by the parasites E. obliquus and E. subterminalis

(figs. 20, 23 and 26) and the host E. ocellaris. Both parasites were bred in large numbers from this host. All second brood

E. obliquus larvae emerged between the first week of August and

mid-September, whereas larvae of the second brood of E. subterminalis

emerged between the third week of September and the first week of

November. These dates tie up with the respective life history differences, i.e. all second brood E. subterminalis larvae develop

into diapausing pupae whereas the second brood of E. obliquus diapause

as first instar larvae.

Using the data obtained by these three sampling methods which

are summarised in the histograms (figs. 20-32), detailed descriptions

of the life histories of 11 of the most common species are given below.

E. subterminalis

This species was by far the most abundant in the samples taken

by the above three methods. There is very strong evidence for it

being bivoltine. Adults of the first brood are on the wing from

mid-May until the end of June with peak numbers occurring at about

mid-June (fig. 20). Emerging larvae of this generation reach a

peak of abundance in mid-July. Second generation adults are then found from the beginning of August until mid-September. The second

generation larvae emerge between mid-September and mid-November and all develop into diapausing pupae. These pupae overwinter and the adults begin emerging the following May (see below). 65

There were some differences between the years 1972 and 1973.

Firstly, the 1973 first generation adults were much more abundant than the second generation ones and greatly exceeded the numbers in

1972; secondly the first generation of 1973 appear to have reached their maximum earlier than in 1972. The latter could be explained by higher temperatures occurring earlier in 1973. This explanation is more convincing if the between year differences of dates of maxima are compared for other species. They nearly all show earlier maxima in 1973 (e.g. E. fascipes, fig. 21). The difference in magnitude between first and second generation adults in 1973 is more difficult to explain. It is assumed that the difference is a real one since it is shown in data from both insect net and Malaise trap catches.

It could be that because of warmer weather the flies were flying more actively and were thus more readily trapped and netted. Another possible explanation is that a proportion of the offspring of the first generation adults went into pupal diapause in 1973. In other words, there may have been only a partial second brood of adults. There is some evidence that this may be usual in A. sylvatica (fig. 31), which otherwise has a similar life cycle. The numbers of flies and emerging larvae collected in samples were much smaller for this species but the histograms again suggest that it is bivoltine. The point to be noted in fig. )1 iu that many of the first generation larvae which emerged from their hosts in mid-July entered diapause; the resulting adults did not emerge until the following spring. Evidently then, this species has only a partial annual second generation.

E. fascipes

Histograms relating to this species and given in fig. 21 strongly suggest that this is a univoltine species. The adults and larvae showed only one peak and all emerging larvae developed into diapausing pupae which overwintered. As with the first brood adults of 66

E. subterminalis the 1973 peaks were earlier than the.1972 ones.

P. campestris Inspection of the larval emergence periods for 1972 and the insect net samples for 1972 suggest that this species is trivoltine

(fig. 29). When the insect net and 1973 Malaise trap samples are included the interpretation is not quite so clear. The numbers in the last two sets of histograms are much smaller, however.

E. fascipes, E. subterminalis and P. campestris exemplify three basic types of life history, i.e. the species are uni-, bi- and trivoltine respectively with overwintering in the pupal stage.

Additional evidence in support of this interpretation is found in the mean adult emergence dates. Most of the diapausing pupae of the above three species were left in an outdoor insectary and in the following year (1973) were examined each day and the appearance of the adults was noted. The first to emerge was a male P. campestris on 9 May and the last, a female E. fascipes, on 13 June. I t' tests were carried out to compare the mean dates of emergence of each species

In making the calculations the date 9 May was called day 1 and hence

13 June became day 36. The means, standard deviations and standard errors of emergence dates are given below.

No. Mean Emergence Day S.D. S.E.

P. campestris 10 6.40 (14 - 15 may) 5.46 1.72 E. subterminalis 8 23.12 (31 May - 1 June) 4.97 1.75 E. fascipes 9 32.55 (9 - 10 June) 2.60 0.86

The 't' tests show that P. campestris emerges significantly earlier than E. subterminalis (t = 6.714 P<0.001) and E. subterminalis significantly earlier than E. fascipes (t * 4.988 P(0.001)

The three parasites attack a common reservoir of hosts (i.e. grassland Cicadellidae, see Table 5) and the above emergence sequences 67

could be expected if the parasites are respectively tri-, bi- and univoltine.

E. obscurus

This species has the same type of life cycle as E. subterminalis and is bivoltine (figs. 22 and 25). This is most clearly shown in fig. 25 where the Malaise trap and insect net samples for 1972 and

1973 have been added together.

E. obliquus and C. semifumosus

These two species have been grouped together because they are both bivoltine and overwinter as first instar larvae within their leafhopper hosts. This interpretation of the life cycle of

C. semifumosus agrees with that of Rothschild (1964). There is one point of difference, however, in that he suggests that the first adults emerge in early July and the second generation adults in late

July and early August. The data from this study indicate that these dates are approximately two weeks too early. E, obliquus and

C. semifumosus have a fourth type of life cycle compared with those of the species so far considered.

E. zonellus Collin, E. zonatus Zetterstedt and P. thomsoni Becker

None of these species was bred but the seasonal appearance of the adults in the histograms of figs. 27, 28 and 30 suggests a univoltine life history.

V. aucta

The hosts of this species are univoltine so only one generation of the parasite is to be expected (Whittaker 1969). V. aucta differs from all other pipunculids sampled in that the catches were almost 68

entirely composed of females. In the other species.of Pipunculidae

sampled the males were the dominant sex.

Many other species were found at Silwood Park but the numbers

taken were not large enough to construct histograms. The probable

life histories of some of these may be inferred as below.

C. curtifrons

This species overwinters as first instar larvae in adult

Stenocranus minutus, as already shown by May (1971). The host is

univoltine and it is almost certain that so is the parasite. There

is very strong evidence that the species is monospecific (see Section A).

P. zugmeyeriae

All Silwood Park records for the adults extend from the end of

May until mid-July. Some 12 larvae were bred from the univoltine

host Emphmatrus ventralis and all formed diapausing pupae. It

is most probable that this is again a univoltine species.

P. fonsecai

Only a few adults were taken and just 2 larvae were bred from

the univoltine Doratura stylata. The larvae formed diapausing pupae

so this pipunculid species appears to be univoltine.

V setosa

All Silwood Park records for the adults are for May and the

4 first week in June. The species is known to parasitise Oncopsis

flavicollis which is univoltine. All bred larvae produced diapausing

pupae. Again this parasite is probably univoltine. 69

Fig. 18. - A Malaise trap. This trap is based on a design illustrated by Chanter (1965).

Fig. 19. - Wing of a Pipunculid. Wings were measured - from the humeral cross-vein to the wing tip as indicated. 70

Fig. 20. - Eudorylas subterminalis : numbers of adults taken in a Malaise trap and with an insect net at Silwood Park represented as ' solid columns; emergence periods of larvae from hosts represented as open columns and dotted columns. (Larvae of non-diapausing pupae = open columns; larvae of diapausing pupae = dotted columns.) The dotted lines under the histograms represent the times of year when samples of Pipunculidae were taken. 71

z0

CI. tn

3

• -r 5

0

Fig. 21. - Eudorylas fascipes Barred columns represent numbers,of females and solid columns numbers of males; otherwise explanation as for fig. 20.

• 4 • •

Fig. 22. - Eudorylas obscurus 15; Insect Net 10. 1972

et ge I El Ea i F I-- - 4 I:EJ ■5', Larval Emerg 1972 Crt? 10' Ca

1,0 -+- N.) Mal Trap • 1973 pu iiiLattut =NV N.) • 15— Insect Net 10. 1973 I I _ F-J 0 c+ 15,- Mal Trap Fig. 23. - Eudorylas obliquus O 10— 1972 0

11■11 MEN co Insect Net O ID_ 1972

SIT MI I. 1-6 —1 0.1Q 15— Larval Emerg 10._ 1972

. 03 eV,

us F-

P 15 • Mal Trap

or. 1973 I3

' 5.—

Nov

4 • •

Insect Net Fig. 24. - Cephalops semifumosus lor- 1972 i.t w 51- 04 1 — i Mal Trap+Insect Net i.) 101-- (1972+1973) : ..P. ■ 51- 1 tv 1 1 IEIMIZ- vi I +- T r ia) 1 Larval Emerg 1 P. lOr 1972 N 5- CS\ 1 h-- Fig. 25. - Eudoryias obscurus dxa Mal Trap*Insect Net (1972+1973) uuT ig

- —y. +— l'' t I

uon 1 Larval Emerg I 1 v 10T 1972 1 1 I s 1- • 1

oj e rrs .11-4 trin a 2t;

•s Eudorylas obliquus 1 Mal Trap+Insect Net Fig. 26. -

oz tor (1972+1973) 51--

Larval Emerg I 10,7 1972

Apr May Jun Jul Aug Sep Oct Nov

• • •

Fig. 27. - Eudorylas zonatus

Mal Trap K - 1972 5-

Insect Net 10;-- 1972

Mal Trap 101- 1973 co • Ehm

0 c+ Fig. 28. - Eudorylas zonellus 0

co 1 Mal Trap 105: 1972 1-$ Insect Net Ia- 1972

Insect Net 1 101- 1973

171 I-- Nov May Jun Jul Aug Sep Oct IP • •

Fig. 29. - Pipunculus campestris

Insect Net 12— 1972 5H r- Larval Emerg 10- 1972

AN- r Mal Trap 10 - 1973

L Insect Net lo- 1973 E x

pl -1 a nati on Fig. 30. - Pipunculus thomsoni a s f

o Mal Trap r fi 10; 1972 5- gs

. 2 Insect Net 101-- 1972 0 and 21 MOM 1- -r- Mal Trap . 101- 1973 .

Iler+VA•Mi —4. Insect Net 10l- 1973 51.-1 ti

May Jun Jul Aug Sep Oct Nov • •

Fig. 31. Alloneura sylvatica

Mal Trap 1011" 1972 5:-

1 — r -1 0'4 ; Larval Emerg CO lOr 1972 31

and r — Mal Trap 101 - 1973 32

. 'swot:4.1 - E x pl an ati Fig. 32. - Verrallia aucta on a

s f Mal 10 1972 o 5r- r fi

gs Insect Net

. 2 lor 1972 0

a — -r r nd Mal Trap

2 101 1973 1 .

Insect Net [Oh 1973 51

May Jun Jul Aug Sep Oct Nov 77

• SECTION C

FIELD OBSERVATIONS ON THE OVIPOSITION BEHAVIOUR OF yERRALLIA SETOSA,

Two illuminating accounts of oviposition behaviour in Pipunculidae

are given by Jenkinson (1903) and Williams (1918). Jenkinson observed

Verrallia aucta hovering poised in the air when an adult of the

Philaenus spumarius L came into view. If the latter was in a

"favourable position" the fly pounced upon it. Williams, studying

pipunculids parasitising sugar cane leafhoppers, mentions how "the

female fly is sometimes deceived into snatching momentarily at leafhopper

moult skins". This immediately indicates the importance of vision in

host detection. Field observations on oviposition by Verrallia

setosa at Silwood Park also demonstrate the importance of vision.

Verrallia setosa is a parasite of Oncopsis flavicollis L which

lives on birch trees. The nymphs of this leafhopper are usually

uniformly reddish brown, although colour variants do occur; a

typical form has two squarish yellow spots at the base of the abdomen.

. On the evening of 21 May, 1972, several ovipositions into the nymphs

were observed. The female flies were seen to hover about two

centimetres away from the birch leaves and twigs while searching

for hosts. Yhen'in view" the flies would orientate themselves into

a position for pouncing on to the nymphs. Injection of the eggs

was completed after no more than three seconds. The nymphs showed

no or very little sign of movement before, during or after the attack;

they remained clinging firmly to the tree. In this way oviposition

differs from the reports given by the above two authors where the

pipunculid either held the victim in the air for injection of the

egg or was flung forward while clinging to the jumping leafhopper. 78

The nymphs of O. flavicollis have never been seen to hop, all

movements are by comparatively slow crawling. This is no doubt

associated with their tree dwelling habit.

Before seizing the nymphs the females of V. setosa were

observed to make distinct pouncing movements on to the host which

were quite different from the normal settling of the fly when coming

-to rest or to take honeydew. These pounces were also made on to

the buds and bud scales, which are of the same size and colour as

Oncopsis nymphs. This clearly suggests the following :-

(a) the initial stages of host detection are entirely visual;

(b) the nymphs mimic the bud scales so as to avoid detection.

Out of 12 "ovipositions" observed four were into Oncopsis nymphs and eight were attempted ovipositions into the buds or bud scales.

The latter involved more than simply pouncing on to the plant; the flies were seen to lower their ovipositors, apparently in an attempt to pierce the bud.

Individual female flies whose searching movements were followed for periods up to 10 minutes were seen to spend two or three minutes closely examining the birch leaves and twigs. They would then suddenly make a rapid and direct flight movement away from the bunch of leaves they were "scrutinising", sometimes to disappear from view completely and at other times to reappear two to four feet away, where they resumed their close searching behaviour. This behaviour pattern has the obvious advantage of allowing more searching over a wider area. 79

SECTION D •

THE TAXONOMY OP PIPDNCULID LARVAE

Eighteen species of Pipunculidae were bred out at Silwood

Park. The mature larvae and puparia of seventeen species,

representing six out of the eight British genera, were examined

in detail with the optical and scanning electron microscopes.

The structure of the larval mouthparts and posterior spiracular

plate were found to be the most useful characters in taxonomy.

A key has been constructed for the identification of the genera

and, in some instances, of the species.

Pre aration of Larvae and Pu•aria for Examination

Since it is the last larval instar integument which forms the puparium in cyclorrhaphous Diptera, the chitinised parts of the mature larvae are attached to or left in the puparium wall during its formation. These chitinised structures include the prothoracic and posterior abdominal spiracles and the mouthparts.

The pupal integument is membranous, the only chitinised parts being the spiracles which are pushed through the wall of the puparium (fig. 71); these provide the only communication between the pupa and the air.

The mouthparts were dissected out after softening first in

10% potassium hydroxide for approximately 24 hours. The drawings

(figs. 33-39) show the appearance of the mouthparts after removal of the labrum and dorsal wall of the pharynx followed by flattening between a slide and coverslip. The paraclypeal phragmata have been opened outwards so that their inner surfaces are revealed after flattening. 80

Specimens for examination with the scanning eleCtron microscope were coated with gold using the diode sputtering coating apparatus (Polaron) in the Zoology Department of Imperial

College. The coated specimens were examined with the Cambridge

Stereoscan Mark 2A microscope in the Botany Department, Imperial

College.

The Homoloies of the Larval mouthparts as used in the Key below

Fig. 33 shows the interpretation of the mouthparts as made here. This is largely the same as that given by Hartley (1963) for the mouthparts of Eristalis. The figures are somewhat schematic and only the three most extensively sclerotised parts are outlined, i.e. mandibular hooks, labial plates and paraclypeal phragmata. Two sclerotised strips (not indicated) extend from the ventral part of the paraclypeal phragmata to the bases of the mandibles; these probably correspond to the tentorial bars described by Hartley in Eristalis. A transverse sclerotised strip lying at the bases of the labial plates and just anterior to the opening of the salivary duct is also described by Hartley, who considers it as the homologue of the so-called intermediate hypopharyngeal or H-shaped sclerite of other cyclorrhapha. 81

KEY TO MATURE LARVAE AND PUPARIA. OP PIPUNCULIDAE BRED AT SILWOOD PARK

The following abbreviations are used in the key : P.S.P., Posterior Spiracular Plate P,R..H., Prothoracic Respiratory Horn L.P.S., Larval Prothoracic Spiracle

.1 Mandibles with tips hooklike (figs. 33-37, 75, 77, 78 and 79) or rounded (fig. 38). Larvae not parasites of Cixiidae or Delphacidae 5 - Mandibles not hooklike or rounded but with sawlike cutting edge (fig. 39). Larvae parasites of Cixiidae or Delphacidae Cephalops Fallen 2

2 Parasites of Cixius pilosus Olivier or Stenocranus minutus Fabricius 4 - Not parasites of C. pilosus or S. minutus 3

3 P.S.P. deep (figs. 41 and 64). For known hosts see Table 5 C. ultimus Becker • P.S.P. shallow (figs. 40 and 65). P.R.H (fig. 69) C. semifumosus Kowarz

4 Parasite of S. minutus and probably specific to it. P.S.P. (fig. 66) C. curtifrone Coe - Parasite of C. ilosus and perhaps other Cixius species. P.S.P. and P.R.H. figs. 67 and 68) C. furcatus Egger

5 Labium a single structure (figs. 37 and 38) . P.S.P. large and round (figs. 49, 50, 51 and 52) Verrallia Mik 6 - Labium a paired structure (figs. 33-36, 39, 75, 76, 77, 78 and 79) 7

6 Parasite of Oncopsis flavicollis L. Mandibles rounded at tips (fig. 38). P.S.P. as in figs. 49 and 52. V. setosa Verrall - Parasite of Neonhilaenus lineatus L and Philaenus spumarius L. 50 Mandibles hooklike at tipTITIT37) . P.S.P. as in figs and 51 V. aucta Fallen

7 Paraclypeal phragmata long and thin (fig. 36). Sides almost parallel Eudor las Acz61 8 - Paraclypeal phragmata triangular in outline figs. 33, 34 and 35) 10 8 P.S.P. very shallow (figs. 45 and 63). Known to parasitise three species of Macrosteles Fieber. . E. fuscipes Zetterstedt - P.S.P. deeper (figs. 46, 47, 59, 60, 61 and 62). Not known to parasitise Macrosteles 9 82

9 P.S.P. deep (figs. 47 and 59). Labial plates not truncate at tip and with teeth extending half way down inner edges (only visible in Stereoscan electron micrographs) (fig. 78) For known hosts see Table 5 E. obscurus Coe - P.S.P. shallower (figs. 46, 60, 61 and 62) E. obliquus Coe E. subterminalis Collin E. fascipes Zetterstedt

10 The most anterior sensory pit on labial plates centrally situated (figs. 33 and 79). Mandibles as in figs. 33 and 79. P.S.P. as in figs. 42, 44, 53, 54, 55 and 56. Pipunculus Latreille 11 - Sensory pi-Gs on labial plates all basally situated (figs. 34 and 35). In Dor]iorhay_,..222 the anterior pit may be a third of the way between the basal and distal edges of the labial plate. In this genus, however, the mandibles are unlike those of Pipunculus (fig. 35) and the puparial integument is generically distinct (fig. 81) 12

11 P.S.P. deep (figs. 42 and 56). Parasite of Graphocraerus ventralis Fallen and probably specific to it P. zugmayeriae Kowarz - P.S.P. shallow (figs. 44, 53, 54 and 55). L.P.S. of P. campestris as in fig. 73. P. fonsecai is a parasite of Doratura stylata and is probably specific to it. For hosts of P. campestris see Table 5 P. campestris Latreille P. thomsoni Becker P. fonsecai Coe

12 P.S.P. very broad and narrow (figs. 43 and 57). Mouthparts as in fig. 34. L.P.S. as in fig. 74 .. A. sylvatica Meigen - P.S.P. deeper and rounded (figs. 48 and 58). Mouthparts as in fig. 35 D. haemorrhoidalis Zetterstedt D. xanthopus Thomson 83

DETAILED DESCRIPTIONS OF LARVAE AND POPARIA

Verrallia Mik

Verrallia has been grouped with Chalarus (Aczel 1948) in the

Chalarinae, which is the more primitive of the two sub-families of

Pipunculidae. The unpaired condition of the labium .(labial plate) is a diagnostic character for the larvae of the two species of

Verrallia examined. In the genera Pipunculus, Cephalops, Eudorylas,

Alloneura and Dorylomorpha (Pipunculidae) the labium is paired.

The two species, V. setosa and V. aucta, may be readily distinguished by the shape of the mandibles (figs. 37 and 38).

Cephalops Fall‘n

The saw edge shaped mandibles of the larvae provide a good generic character. The costal stigma, thorax with two dorsocentral lines of hairs and the propleural fan of hairs characterise the adults. Cephalops is clearly a valid genus biologically since all known breeding records have been from the Delphacidae and

Cixiidae (Fulgoromorpha). No other genera are known to parasitise the latter. C. ultimus and C. semifumosus parasitise a common host reservoir (Table 5). They can be fairly easily distinguished on the basis of the posterior spiracular plates (figs. 40, 41, 64 and

65). The posterior spiracular plates in C. furcatus and C. curtifrons are very similar (figs. 66 and 67). However, the hosts of these two species are very different (Table 5) so misidentifications of larvae are unlikely. C. germanicus Aczel is closely allied to

C. furcatus so it is quite likely that its host will also be a cixiid.

Eudorylas Acz41

Twenty-two species of Eudorylas occur in Britain. Five were bred out in the present study. The long, extended, almost parallel-

84 sided paraclypeal phragmata characterise the mature larvae of Eudorylas (fig. 36). One species, E. fuscipes, may be fairly readily distinguished by its shallow posterior spiracular plate (figs. 45 and 63). It is also the only Eudorylas species which has been bred from Macrosteles sexnotatus Fallen at Silwood

Park. M. laevis Ribaut and M. variatus Fallen are two other known hosts of this parasite. The other four Eudorylas species cannot be readily identified. A knowledge of the host does not help much in their identification because they.all parasitise a common host reservoir (Table 5). E. obscurus has a deep posterior spiracular plate (figs. 47 and 59). The posterior spiracular plates of E. subterminalis, E. obliquus and E. fascipes are shallower than in E. obscurus but are otherwise very similar.

(figs. 46, 60, 61 and 62). The scanning electron micrographs show E. subterminalis and E. obliquus to have truncate anterior edges to the labial plates with teeth only along the anterior edges (figs. 75 and 76). In E. fascipes and E. obscurus the anterior edges are more pointed and the teeth extend half way down the inner edges in E. obscurus and about one third of the way in E. fascipes (figs. 77 and 78). These observations are based on the examination of only one specimen of each species.

These differences can only be seen in the Stereoscan micrographs but are nevertheless of interest as they show where the natural affinities between species lie even though the differences may not be useful for the practical purposes of species identification.

Pipunculus Latreille

This is an interesting genus because the posterior spiracular plate of P. zugmayeriae resembles that of the four last-mentioned species of Eudorylas, whereas the posterior spiracular plates of P. thomsoni, P. campestris and P. fonsecai have a distinctly different shape (figs. 42, 44, 53, 54, 55 and 56). However, the structure of the larval mouthparts and adult morphological characters leave little doubt that the true systematic position of zugmayeriae is within the genus Pipunculus.

P. thomsoni, P. campestris and P. fonsecai cannot be distinguished by their posterior spiracular plates. In the adult males of these species, the genitalia do not provide specific differences. In all other species of Pipunculidse examined, the male genitalia were found to provide absolute characters for species identification. The key characters already given by Coe (1966), i.e. the absence of greyish side margins on the abdominal tergites in P. campestris and the presence of swollen hind femora in

P. thomsoni, are used to distinguish the males of these closely allied species. The adult females of these three species are more readily distinguishable (Coe 1966). For the species

P. campestris and P. fonsecai there is the biological difference referred to earlier, i.e. P. fonsecai is most probably univoltine and host specific to Doratura stylata, whereas P. campestris is at least bi- and possibly trivoltine with nine known hosts. It is perhaps significant that these nine do not include D. stylata.

P. thomsoni was not bred at Silwood Park although the adults occurred quite commonly in June and July (Section B). The electron micrograph of the posterior spiracular plate of P. thomsoni was made from a puparium of a female bred by A.H. Hamm which is now in the

Hope Department of Entomology, Oxford.

Dorylomorpha Acz41

The two species D. haemorrhoidalis and D. xanthopus were bred out. The posterior spiracular plates are very similar (figs. 48 86 and 58). Generically the puparia are quite distinct. They are sculptured with conspicuous V-shaped impressions'in two lines on the dorsal surface which are connected by transverse furrows

(fig. 81). In the other genera examined the puparia are more rounded and barrel shaped. They also lack the deep impressions found in Dorylomorpha. The pupal prothoracic spiracles project through the wall of the puparium and have the spiracular openings on papillae arranged on large ring-like protuberances (fig. 70).

In the other genera the papillae are borne on less pronounced protuberances (figs. 68, 69, 71 and 72). The pupation site of

Doilaal.amm differs from that of the other genera. Coe (1966) mentions (p. 42) a puparium of D. xanthocera Kowarz bred in

Bohemia which was fixed to a twig. In the present study all bred larvae of Dorylomorpha attached themselves to the foodplant or glass wall of the rearing tube to pupate. The other genera pupated on or just below the surface of the sand. It is suggested that this may be an adaptation to living in wet habitats liable to flooding. It is significant that two out of the four hosts recorded for D. haemorrhoidalis and D. xanthopus, i.e. C. quadrinotata

Fabricius and E. obsoletus Kirschbaum live in wet grassland normally where Juncus is growing. Habitats at Silwood Park where these leafhoppers were collected are often flooded with water to a depth of several centimetres. 87

SENSORY RECEPTORS ON THE LABIAL PLATES •

Under the light microscope small non-sclerotised pits are

visible on the labial plates. More light is transmitted through

them so they appear as clear circles, generally about four in

number. Scanning electron micrographs of these pits in P. fonsecai

(figs. 79 and 80) show two types of probable sensory receptors.

From their position it may be inferred that they are gustatory.

The specimens examined were prepared from larvae that were left

in 10% potassium hydroxide to facilitate the dissection of the

mouthparts so that the appearance in figs. 79 and 80 is to some

extent artificial. Sections of fixed material would have to be

examined for a thorough investigation of these receptors. The

micrographs nevertheless strongly suggest that these are sensory

receptors. Other authors, e.g. Hartley 1963, mention the presence

of sensory pits on the labial plates but I have not come across

any electron microscope studies of these sense organs situated

in pits.

• Exaanation of Fig§L_Iimli

Mouthparts of mature larvae of :

Fig.

33 P. campestris

34 A. sylvatica

35 D. haemorrhoidalis 36 E. subterminalis

37 V. aucta

38 V. setosa

39 C. semifumosus

Scale line = 0.1 mm.

• 88

labial plate

mandible

paraclypeal phragma

MEM

Fig. 33 89

4

a

• 90

•

• 91

•

•

0 92

•

N CO

LL

•

93

cc co th LL 94

•

4 Explanation of Figs. 40-50

Outline drawings of Posterior Spiracular Plates of :

1111E. 40 C. semifumosus

41 C. ultimus

42 P. zugmayeriae

43 A. sylvatica

44 P. campestris

45 E. fuscipes

46 E. subterminalis

47 E. obscurus

48 D. haemorrhoidalis

49 V. setosa 50 V. aucta

Scale line = 0.1 mm. 95

Fig. 40 Cephalops semifumosus

Fig. 41 Cephalops ultimus • 4

Fig.42 Pipunculus zugmayericie 97

Fig.43 Alloneura sylvatica

Fig.44 Pipunculus campestris

Fig.45 Eudorylas fuscipes 98

46 Eudorylas subterrninalis

Fig.47 Eudorylas obscurus 99

Fig. 48 Dorylomorpha haemorroidatis

Fig.49 Verraflia setosa 1

Fig.50 Verrallia aucta Explanation of Stereoscan Electron Micrographs, Figs. 51-81

Figs. Posterior Spiracular Plates of :

Fig. 51 V. aucta 52 V. setosa 53 P. campestris 54 P. thomsoni 55 P. fonsecai 56 P. zugmayeriae 57 A. sylvatica 58 D. xanLhopus 59 E. obscurus 60 E. subterminalis 61 E. fascipes 62 E. obliquus 63 E. fuscipes 64 C. ultimus 65 C. semifumosus 66 C. curtifrons 67 C. furcatus

Lia. 61m/a Prothoracic Respiratory Horns of : Fig. 68 C. furcatus 69 C. semifumosus 70 D. haemorrhoidalis 71 P. camoestris 72 P. thomsoni

Figs. 73 and 74 Larval Prothoracic Spiracles of

Fig. 73 P. campostris 74 A. sylvatica

Figs. 75-80 Mouthparts of mature larvae of :

Fig. 75 E. obliquus 76 E. subterminalis 77 E. fascipes 78 E. obscurus 79 P. fonsecai 80 P. fonsecai (sensory pit in fig. 79 enlarged)

EiLt____a D. haemorrhoidalis - part of puparium 101

Fig. 51. V. aucta (x 240)

Fig. 52. V. setosa (x 282) 102

Fig. 53. P. campestris (x300)

Fig. 54. P. thomsoni (x 285)

1 V1

Fig. 57. A. sylvatica (x 360)

Fig. 58. D. xanthopus (x 270) 16'j

Fig. 59. E. obscurus (x 298)

Pig. 60. E. subterminalis (x 286) Fig. 61. E. fascipes (x 294)

Fig. 62. E. obliquus (x 274) 107

Fig. 63. E. fuscipes (x 315)

Fig. 64. c. ultimus (x 297) 108

Fig. 65. c. s emifumosus (x 334)

Fig. 66. C. curtifrons (x 339)

IUj

•

Fig. 67. C. furcatus (x 280)

•

Fig. 68. C. furcatus (x 285) •

Fig. 69. C. semifumosus (x 720)

I Ik

•

Fig. 70. D. haemorrhoidalis (approx. 800) 111

Fig. 71. P. campestris (x 944)

•

•

Fig. 72. P. thomsoni (x 708) 112

A

Fig. 73. P. campestris (r 1980)

Fig. 74. A. syivatica (x 1670) 113

Fig. 75. E. obliquus (x 572)

•

Pig. 76. E. subterminalis (x 796) 114

Fig. 17. E. fascipes (x 262)

Fig. 78. E. obscurus (x 550) 115

Fig. 79. P. fonsecai (x 664)

•

Fig. 80. P. fonsecai (x 4770) 116

*

Fig. 81. D. haemorrhoida1is (x 49) AI 1i 7 SECTION E

THE TAXONOMY OF ADULT PIPUNCULIDAE •

The nomenclature and classification adopted in this study are after Collin (1945) as detailed by Coe (1966). The present studies on larval taxonomy lend good support to the division of the family into eight genera as being a natural classification. The following

36 species have been found at Silwood Park.

CHALARINAE CHALARUS Walker spurius Fallen latifrons Hardy fimbriatus Coe? pughi Coe argenteus Coe? VERRALLIA Mik aucta Fallen villosa von Roser setosa Verrall beatricis Coe

PIPUNCULINAE ALLONEURA Rondani sylvatica Meigen nigritula Zetterstedt kuthyi Aczel DORYLOMORPHA Aczel haemorrhoidalis Zetterstedt imparata Collin xanthopus Thomson PIPUNCULUS Latreille zugmayeriae Kowarz campestris Latreille thomsoni Becker fonsecai Coe CEPRALOPS Fallen furcatus Egger obtusinervis Zetterstedt curtifrons Coe aeneus Fallen ultimus Becker subultimus Collin titania Coe semifumosus Kowarz

- 118

EUDORYLAS Aczel fascipes Zetterstedt obliquus Coe (jenkinsoni Coe) subterminalis Collin longifrons Coe obscurus Coe zonatus Zetterstedt zonellus Collin fuscipes Zetterstedt kowarzi Becker?

The taxonomy of the adult British Pipunculidae has been recently revised by Coe (1966). Probably this family has been more thoroughly investigated in Great Britain than in other parts

Of the world. A great deal of taxonomic and morphological work is still required in this poorly known family. A good illustration

Of this is to be found in Appendix C of this thesis where nine new

Species are described from a large collection of 44 species of

Pipunculidae made near Stuttgart in West Germany during the summer of 1974.

In the following pages I describe most of the species in the

Subfamily Pipunculinae found at Silwood Park, particular emphasis being placed on the male genital structures. Morphological investigations of the male genitalia have been successfully used by Hardy (e.g. 1943) in his numerous surveys of the Pipunculidae ih different geographical regions. No such study of the British representatives had been made up to the present investigation.

,The Homologies of the Sclerotised Parts of the Male Genitalia

The postabdomen (segments 6 and following) is asymmetrical hb in many Other cyclorrhaphous Diptera where circumversion has

Occurred. The sternites from segment 6 onwards are displaced up an to the left side Of the abdomen (fig. 82). In general it is the claspers(genital styles or harpagones of other authors) which

provide the diagnostic characters to the species. The proportion of

the inflected to non-inflected parts of the sixth abdominal sternum,

the shape of the aedeagus and sperm pump apodeme and the extent of

the apical membranous area on the eighth abdominal segment also

provide very useful characters.

The drawings of the ventral views of the male postabdomen are

based on potashed material. They were prepared in the usual way by

leaving the abdominal segments in 10% potassium hydroxide for 48 hours.

The wing lengths given are from the humeral crossvein to the wing tip.

All the following descriptions refer to the males unless otherwise

stated.

DESCRIPTIONS OF SOME BRITISH PIPUNCULIDAE

EUDORYLAS Aczel

Group I

Pour anterior tibiae with a distinct posteroventral spur at tip;

humeri yellow; bases of femora distinctly yellow; costal stigma

complete; eighth abdominal segment of male with membranous area.

The males of four out of the six British species are described here. E. terminalis Thomson is described in Appendix C from W. German specimens.

E. fascipes Zetterstedt

Male Abdominal segment 8 with large round apical membranous

area. The moderately long and coiled terminal portion of the

aedeagus with a chitinised projection at base (fig. 83(b)).

Claspers as in fig. 83.

Wing length 2.907-3.619 mm; mean 3.298 mm. Based on 125 Silwood

Park males. Wing-length 2.670-3.560 mm; mean 3.137 mm. Based on 32 males

from Stuttgart. I 120

Female Ovipositor with base round, without a longitudinal groove dorsally; piercer short and straight.

E. subfascipes Collin

Male Abdominal segment 8 with membranous area extending the full depth of the segment (Coe, fig. 144). Inflected portion of the sixth abdominal sternum very narrow (fig. 84). Terminal part of aedeagus very long and coiled (fig. 84(b)). Claspers as in fig. 84.

Wing lengths of 2 males examined 4.588 mm; 4.627 mm.

This species has not been found at Silwood Park.

The drawings of the male genitalia are based on British

specimens in the British Museum. E. subfascipes is the

largest of the Group I species; the long coiled aedeagus,

narrowly inflected sixth abdominal sternum and the shape

of the claspers readily distinguish it from the other

species.

E. obliquus Coe (E. jenkinsoni Coe)

Male Abdominal segment 8 with moderately large and roughly triangular membranous area (Coe, figs. 145 and 147). Sixth abdominal sternum very deeply inflected (fig. 85). Aedeagus not terminating in a coiled filament (fig. 85(b)). Epandrium (Tergite 9) with a narrow projection on left side. Claspers as in fig. 85. Wing length 2.927-4.034 mm; mean 3.606 mm. Based on 49 males from Silwood Park.

I have examined the types and potashed specimens of

Dbliquus and jenkinsoni determined by Coe and have little

doubt that they are the same species. 121

E. subterminalis Collin

Male Abdominal segment 8 with small apical membranous area

(fig. 11, Collin 1956). Extent of inflected part of sixth abdominal sternum about equals that of the non-inflected part.

Sixth abdominal tergum (i.e. the part of the tergum which has been displaced ventrally) with a hooked process (fig. 86). Aedeagus with a short terminal filament (fig. 86(b)). Claspers as in fig. 86.

Wing length 2.887-3.935 mm; mean 3.527 mm. Based on 365 males from Silwood Park.

Wing length 2.591-3.461 mm; mean 3.169 mm. Based on 63 males from Stuttgart.

The hooked process on tergum 6 appears to be a

unique character. The allied species E. terminalis

Thomson (Appendix C) has a wartlike protuberance in a

corresponding position but it is at most only slightly

curved over.

GROUP II

Four anterior tibiae with a distinct posteroventral spur at tip; humeri yellow; bases of femora dark; costal stigma complete; eighth abdominal segment of male with membranous area.

Four British species belong in this group. The male genitalia of one of these, E. arcanus Coe, have not been examined.

E. longifrons Coe

Male Abdominal segment 8 with large apical membranous area

(fig. 113). Claspers, aedeagus and sperm pump apodeme as in fig. 87.

Wing lengths of 2 males from Silwood Park 3.797 Earn; 4.489 mm.

Wing lengths of 3 males from Stuttgart 4.311 mm; 4.370 mm; 4.548 mm. 122

E. obscurus Coe

Male Abdominal segment 8 with large apical membranous area

(fig. 114). Claspers, aedeagus and sperm pump apodeme as in fig. 88. Wing length 3.144-3.836 mm; mean 3.538 mm. Based on 82 males from Silwood Park. The male genitalia of the above two species are

similar. In Coe's key the species separate into different

couplets on the basis of leg colour. The tibiae are black dorsally for at least apical half in obscurus and yellow

dorsally (at most vaguely darkened for slightly more than

apical half) in longifrons. E. longifrons is distinctly

larger than obscurus (see above wing lengths). The apical

margin of the left clasper is more hollowed out in obscurus

and the terminal portion of the aedeagus relatively shorter.

The antennae are more sharply pointed in obscurus. The

length of approximation of the eyes is less than the length

of the frontal triangle in obscurus; in longifrons the

length of approximation of the eyes is greater than the

length of the frontal triangle.

E. zermattensis Becker

Male Abdominal segment 8 with large apical membranous area

(fig. 169, Coe p.72). Inflected part of sixth abdominal sternum much shallower than in obscurus (fig. 89). Aedeagus resembling that of E. zonatinus sp.n. (Appendix C) but shorter. Claspers quadrate with rounded apical margins (fig. 89).

Wing lengths of 2 males collected from sand dunes in Glamorgan 2.947 mm; 2.986 mm. The species is the smallest of the lattermost three

and easily distinguished from obscurus by the shape of the 123

claspers. The male genitalia most closely resemble

those of the non-British zonatinus sp. n. (Appendix C).

The latter has black humeri so it is unlikely to be confused

with zermattensis. Further comparisons between the two

species are given in Appendix C.

E. zermattensis may be a typically coastal species

in Britain. Apart from the above tro examples from

Glamorgan it has been taken by Collin at Worlington,

Suffolk (Coe, p.74).

GROUP III

Four anterior tibiae with a distinct posteroventral spur at tip; humeri dark brown or black; bases of femora dark; costal stigma complete; eighth abdominal segment with apical membranous area.

Six British species belong to this group; the male genitalia of two, E. inferus and E. unicolor, have not been examined.

E. montium Becker

Male Abdominal segment 8 with moderately large apical membranous area (fig. 115). Claspers as in fig. 90. Aedeagus with a short terminal filament (fig. 90(b)).

Wing length 3.045-3.639 mm; mean 3.480 mm. Based on 7 males from Stuttgart.

E. montium does not occur at Silwood Park. In

Britain it is typically a montane species. It is easily

distinguished from the other three species described in

this group by the short terminal aedeagal filament. The

male genitalia of one British example have been examined

and were found to be similar to fig. 90, which is based on

specimens from Stuttgart. . 124

E. fuscipes Zetterstedt

Male Abdominal segment 8 with large apical membranOus area (fig. 175, Coe p.72). Sixth abdominal sternum relatively small and narrowly inflected (fig. 91). Aedeagus with long and coiled terminal filament (fig. 91(b)). Claspers as in fig. 91.

Wing length 2.729-3.243 mm; mean 2.976 mm. Based on 8 males from Silwood Park.

This species is small. Its overall size, the relatively small sixth abdominal sternum and the shape

of the olaspers readily distinguish it from the other

species in this group.

E. zonatus Zetterstedt Male Abdominal segment 8 with large apical membranous area

(fig. 173, Coe p.72). Aedeagus with long coiled terminal filament

(fig. 92(b)). Claspers and sperm pump apodeme as in fig. 92.

Wing length 3.856-4.430 mm; mean 4.213 mm. Based on 17 males from Silwood Park.

E. zonellus Collin

Male Abdominal segment 8 with large apical membranous area.

Aedeagus with long coiled terminal filament (fig. 93(b)). Claspers and sperm pump apodeme as in fig. 93.

Wing length 4.173-4.865 mm; mean 4.602 mm. Based on 60 males from Silwood Park.

Wing length 4.390-4.884 mm; mean 4.621 mm. Based on 19 males from Stuttgart.

The females of the above two species are readily

distinguishable. The ovipositor of zonatus has a long

and strongly upcurved piercer which is about twice as long

as the base. In zonellus the piercer is only very slightly 125

upcurved and a little longer than the base. Both species • have been taken in copula at Silwood Park and the male

genitalia of mated specimens as well as of many other males

have been examined. A good consistent difference is in

the shape of the sperm pump apodeme (figs. 92(a) and 93(a)).

The claspers of zonellus have the apical margins more

distinctly hollowed out compared with zonatus. This is

apparent in a striotly ventral or lateral facial view

(figs. 92(c)(d) and 93(c)(d)). Both species are fairly

numerous at Silwood Park (zonellus being the more common).

Although neither has been bred out the adult sampling data

suggest they are both univoltine (Section B).

PIPUNCULUS Latreille

P. zugmayeriae Kowarz and P. spinipes Meigen

Aedeagus bifid, reuniting at tip as in fig. 94(f). Sperm pump apodeme small.

P. zugmayeriae Kowarz

Male Third costal segment shorter than fourth. Terga 2-5 with conspicuous greyish side-margins. Halteres dark. Frons shorter than length of approximation of eyes. Aedeagus, sperm pump apodeme and claspers as in fig. 94.

P. spinipes Meigen

Male Third costal segment about equal to fourth. Halteres yellowish. Terga 2-5 with conspicuous greyish side-margins. Frons much shorter than length of approximation of eyes. Clasper° strongly curved in lateral view (fig. 95(e)). Aedeagus resembling that of zugmayeriae. Sperm pump apodeme resembling that of P. oldenbergi

Collin (Appendix C). 126

The above two species are quite closely allied. The

claspers in zugmayeriae taper uniformly to the tip; in

spinipes the basal half is stouter and when seen in lateral

view the claspers are strongly curved (fig. 95(e)).. The

sperm pump apodeme of spinipes resembles that of oldenbergi

(Appendix C) and is more parallel-sided than in zugmayeriae.

The non-British oldenbergi is more closely allied to spinipes

than to zugmayeriae. All three species have the divided

aedeagus which reunites at the tip. P. zugmayeriae may be

distinguished from oldenbergi, apart from the characters of

the male genitalia, on account of (a) its smaller size,

(b) third costal segment much shorter than fourth; in

oldenbergi the third and fourth are about equal, (c) thorax

with brownish dusting dense all over; in oldenbergi only

the anterior half and the posterior quarter are dusted.

P. spinipes and P. oldenbergi are compared in Appendix C.

P. thomsoni Becker, P. campestris Latreille and P. fonsecai Coe

Males When viewed from behind, abdominal segment 8 with membranous area narrower below than above. When viewed from in front, tergum 2 is not entirely shining but partly brownish dusted. Aedeagus tnree- forked at tip. Claspers and sperm pump apodeme more or less as in drawing of P. campestris (fig. 82).

As already mentioned in the section on larval taxonomy, these three species are very closely allied. The male genitalia are similar and cannot be used reliably in their identification. The drawing, fig. 82, was made from a genitalia preparation of P. campestris.

In thomsoni the claspers are generally more rounded on the outer edges but if a long series of specimens are examined the two conditions grade into one another. In the present studies the characters used 127

to separate the three species were those already given by Coe.

The absence of greyish side markings on terga 2-5 separates off campestris from thomsoni and fonsecai. The latter two are distinguished by size (see below) and by the possession of swollen hind femora in thomsoni. In the females the ovipositor has the piercer more strongly downcurved in campestris than in thomsoni.

The tibiae of fonsecai are mainly darkened and those of thomsoni mainly yellow. Biological differences between the three species are given in Section D. P. fonsecai is, as already pointed out by

Coe, a small species. P. campestris is variable in size, while thomsoni is normally a large species.

P. thomsoni Wing length 3.619-4.845 mm; mean 4.180 mm. Based

on 17 males from Silwood Park.

P. campestris Wing length 2.986-4.726 mm; mean 3.949 mm. Based

on 59 males from Silwood Park.

P. fonsecai Wing length of one male, from Silwood Park 3.164 mm.

P. phaeton Coe

When viewed from behind, male abdominal segment 8 with membranous area narrower below than above. When viewed from in front, tergum 2 entirely glittering black. Aedeagus two-forked (fig. 96(g)).

Claspers and sperm pump apodeme as in fig. 96.

I have examined only one specimen of phaeton. The

two-forked aedeagus is apparently a unique character. The

long pointed claspers should easily distinguish it from the

campestris group. It separates out in Coe's key on the

basis of the entirely glittering black second tergum. This

species has not been found at Silwood Park. 128

P. varipes Meigen

When viewed from behind, male abdominal segment 8 with membranous area narrower above than below. When viewed from in front, tergwn 2 is not entirely shining but partly brownish dusted. Aedeagus three- forked. Sperm pump apodeme very large (fig. 97(a)). Claspers with tips rounded (fig. 97).

The shape of the sperm pump apodeme, the rounded tips

to the claspers and the delineation of the apical membranous area characterise this species of Pipunculus.

CEPHALOPS Fall6n

C. semifumosus Kowarz, C. ultimus Becker, C. subultimus Collin, C. titania Coe, C. oberon Coe, C. carinatus Verrall

Male abdominal segment 8 with membranous area extended to base of tergum 9 (epandrium) (figs. 98, 101, and 131).

C. carinatus

This species may be separated out on the basis of the light grey side markings on terga 2-5 (when viewed from behind) and the long

(2-5) black bristly hairs anteriorly on middle third of hind tibiae.

These are the distinguishing characters given by Coe. No British specimens were examined; the drawing of the male genitalia in fig. 131 (Appendix C) is based on a specimen from Stuttgart. The remainder of the species under the above head may be split into two groups on the basis of clasper shape.

(a) semifumosus and ultimus with claspers in ventral view markedly

tapering towards the apex (fig. 98)

(b) subultimus, titania and oberon with claspers in ventral view

slightly tapering towards 'ne apex (fig. 101) Group (a) are typically smaller species than group (b) (see wing lengths below). J. cy

Comparison of C. semifumosus and C. ultimus Males

When viewed from above, semifumosus has tergum 4 partly glittering black; in ultimus terga 2-4 are completely dull. This is how the two species separate out in Coe's key. Further differences can be found in the male genitalia as seen in lateral view (figs. 99 and 100).

The claspers are distinctly curved in semifumosus, the aedeagus has shorter and stouter terminal forks and the "aedeagal sheath" terminates in two long spikes. In ultimus the "aedeagal sheath" terminates in two small rounded projections.

C. semifumosus Wing length 3.144-3.935 mm; mean 3.506 mm.

Based on 23 males from Silwood Park.

Wing length 3.144-3.718 mm; mean 3.375 mm.

Based on 28 males from Stuttgart.

Wing length 2.769-3.303 mm; mean 3.027 mm.

Based on 34 males from near Calw (Black Forest).

C. ultimus Wing length 3.243-3.777 mm; mean 3.553 mm.

Based on 15 males from Silwood Park.

C. oberon Coe

Viewed from above, male with tergum- 3 shining at least posteriorly.

Femora extensively darkened about middle. The species separates out in Coe's key on the basis of these characters. In both titania and subultimus terga 2 and 3 are completely dull when viewed from above.

The aedeagus of oberon is very different from that of subultimus and titania. In ventral view (when aedeagus and claspers are pulled back posteriorly revealing the true ventral surface) (fig. 104(g)), the left fork of the aedeagus is distinctly longer than the other two and all three forks are obviously more dilated at the tips compared with titania and subultimus (figs. 102(g) and 103(g)). The%edeagal sheath" is developed into only one spike (fig. 104), not two as in titania and subultimus (figs. 102 and 103). 130

Comparison of C. titania and C. subultimus Males

The membranous area of the eighth abdominal segment is noticeably

wider in subultimus, occupying about half the width of the segment

(as seen from behind). The "tooth" on the inner apical margin of

the clasper is more pronounced in titania (fig. 103). In titania

the tips of the three-forked aedeagus are scarcely swollen (figs. 103

and 103(g)); in subultimus they are more conspicuously swollen

(figs. 102 and 102(g)). The tips are more obviously inclined to

the main axis of the aedeagus in subultimus (cf. figs 102 and 103).

C. subultimus Wing lengths of 4 males from Stuttgart : 3.658 mm; 3.955 mm; 4.054 mm; 4.311 mm. Wing lengths of 2 males from Silwood Park :

4.014 mm; 4.271 mm.

. furcatus Egger, C. obtusinervis Zetterstedt, C. vitti es Zetterstedt, C. aeneus Fallen, C. curtifrons Coe ..m.1.•■•■•••■• Male abdominal segment 8 with membranous area not extended to base of

tergum 9 (figs, 105, 106, 107, 108 and 109).

C. furcatus Egger

Wing vein M1+2 with an appendix. This character is also shared by

C. germanicus Aczel. The male genitalia of the latter have not been

examined. The claspers of furcatus resemble those of obtusinervis.

Both the aedeagus and sperm pump apodeme are very different, however.

(cf. figs. 105 and 106).

C. obtusinervis Zetterstedt

This species possesses the following unique combination of characters:

black femora which are all brightly polished behind. The aedeagus

is quite unlike that of any other British Cephalops (fig. 106(g)). 131

C. vittipes Zetterstedt and C. aeneus Fallen

Both species have the femora completely yellow in both sexes. In the male the eighth abdominal segment, when viewed from above, is longer in aeneus (i.e. quite half as long as tergum 5), than in vittipes (where it is at most one third as long as tergum 5). Coe illustrates these differences. Further distinct differences are found in the claspers and aedeagus. In aeneus the claspers are asymmetrical (fig. 107); in vittipes they are less extended and are symmetrical (fig. 108). The aedeagi of the two species have two- forked tips. Although these tips are structurally very different

(figs. 107(g) and 108(g)), a common ancestry of the two species is suggested since the aedeagi of all other British Cephalops have three-forked tips.

C. curtifrons Coe

Male Frons strikingly short, not longer than antennae.

C. curtifrons is separated out on the basis of this character by

Coe. The aedeagus has three very short forks at the tip (fig. 109(g)) and is noticeably dilated before the forks. The "head" of the sperm pump apodeme is conspicuously rounded (fig. 109(a)).

ALLONEURA Rondani

Three of the 7 British species occur at Silwood Park.

A. sylvatica Meigen

Male Viewed from behind, abdominal segment 8 with membranous area very narrow. Fourth and fifth sterna with ridges (fig. 110). The claspers are long and slender (fig. 110) with the tips inwardly curved. Hardy (1943) illustrates the male genitalia of a N. American specimen and the clasper shape is in good agreement with fig. 110 based on Silwood Park specimens. The sperm pump apodeme is similar to that of A. kuthyi Aczel (fig. 111(a)). 132

A. kuthyi Aczel

Male Viewed from behind; abdominal segment 8 with'membranous

area circular, occupying at least half the width of the segment.

The hind femora with conspicuous fine posteroventral hairs. Ninth

tergum (epandrium) more elongate and tapering than in sylvatica or

nigritula Zetterstedt (fig. 111). The claspers are stouter than

in sylvatica and the sperm pump apodeme is larger and differently

shaped from that of nigritula (cf. figs. 111(a) and 112(a)).

A. nigritula Zetterstedt

Male Viewed from behind, abdominal segment 8 with membranous

area circular, occupying at least half the width of the segment.

The posteroventral hairs on hind femora are shorter and less obvious

than in kuthyi. The claspers (fig. 112) are not conspicuously

incurved at the tip as in kuthyi. The fourth and fifth sterna

of both kuthyi and nigritula are without the ridges found in sylvatica.

The sperm pump apodeme of nigritula (fig. 112(a)) is smaller and

differently shaped from that of sylvatica or kuthyi.

•

Explanation of Figs. 82-115

Figs. 82-98. 101, 105-112 - Male Postabdomen in Ventral View

Fig. 82 P. campestris 83 E. fascipes 84 E. subfascipes 85 E. obliquus 86 E. subterminalis 87 E. longifrons 88 E. obscurus 89 E. zermattensis 90 E. montium 91 E. fuscipes 92 E. zonatus 93 E. zonenus 94 P. zugmayeriae 95 P. spinipes 96 P. phaeton 97 P. varipes 98 C. semifumosus 101 C. subultimus 105 C. furcatus 106 C. obtusinervis 107 C. aeneus 108 C. vittipes 109 C. curtifrons 110 A. sylvatica 111 A. kuthyi 112 A. nigritula

Figs. 99, 100, 102-104 - Male Ilypopygium in Lateral View

Fig. 99 C. semifumosus 100 C. ultimus 102 C. subultimus 103 C. titania 104 C. oberon

Figs. 113-115 - Male Abdominal Segment 8 in Posterior View

Fig, 113 E. longifrons 114 E. obscurus 115 E. montium

a = sperm pump apodeme b = aedeagus in lateral view c . left clasper in lateroventral view d = right clasper in lateroventral view e = right clasper in lateral view f = aedeagus in lateroventral view g = aedeagus in ventral view

Scale line = 0.5 mm. 133

82

right clasper

i Ct1

' - •- - • ------• - • • • AS- • 111 • • • ott S2

• 11, • alt 1:5

• • ------at rn

• • 140 •

.S2 •

0 as

a 4 a din Ct5

r A 4 145

a f

1 I •

147

9 a

co

s .-...... ------21:::::. 150

100g i00 151

i

)

102 • • 153

1029 1039

104g 154

1

a 155

4

p 156

•

rj

cJ

p

a 158

159 160

a

i - 161

* 162

114

115 163

DISCUSSION

Larval taxonomy of cyclorrhaphous Diptera is notoriously

difficult. Typically the larva is an acephalous maggot living

completely surrounded by its food supply. It is the task of the

adult to search out a suitable food medium into which to lay the

eggs. The larvae do not need to seek out their food and this is

correlated with the absence of well developed and conspicuous sense

organs. The head capsule is completely reduced, the only chitinised

cephalic structures being the mouthparts and internal phragmata.

The whole head is retracted into the anterior part of the thorax.

These features give the larvae of cyclorrhaphous Diptera a very

uniform appearance. Their identification is based as much on

inference from the food medium in which they are found as on strictly • morphological characters. There are of course exceptions, not all

Cyclorrhapha conform to this generalisation. For example, the

work of Hartley (1961) on syrphid larvae shows how species can be

identified exclusively on morphological characters. Syrphid larvae

. do not, however, have the typical acephalous maggot appearance,

their habits are varied and they are freely. endowed with different

types of conspicuous sensillae.

The Pipunculidae and Syrphidae are closely allied. There

are similarities in adult structure and both families have the k posterior pair of spiracles in the mature larva on a disc or plate.

In addition, there is a link between the predatory aphid feeding

habit of some Syrphidae and the parasitic habit of Pipunculidae.

The present studies have shown how the shape of the spiracular

plate may be used in larval and puparial taxonomy. When the 164

structure of the mouthparts is considered together with the shape

of this plate, identifications to the generic, at least to the

species group and sometimes to the specific level, are possible.

Most species, although not host specific, do exhibit some degree

of specificity and if this biological information is considered

in laryae the species may frequently be named. Inferred from

the many dissections of hosts made in this study, it is concluded

that pipunculids have two larval instars. It is only the second

instar which possesses the spiracular plate.

The present work has shown that the genera recognised by

Coe (1966) on adult biological and morphological characters also

holds for the larvae. There is thus further evidence that the

existing classification is a natural one.

It has been shown time and again in the Diptera and other

insect orders that the structure of the male genitalia provides

a reliable and often the only means of distinguishing species

when all else fails. The descriptions of Pipunculidae with illustrations of the male genitalia show how once again these characters alone are of use in species identification. It is

on the basis of structure of male genitalia that two British species, E. obliquus and E. jenkinsoni, described by Coe, may

be'synonymised.

There is one species group where the structure of the male genitalia does not provide a reliable means of distinguishing them. P. thomsoni, P. campestris and P. fonsecai are very closely allied. They are only reliably separated on the basis of tergal dusting only visible in dried specimens, and the shape 165

of the hind femora. However, it is significant that biologically

they are distinct species. P. thomsoni and P. fonsecai are uniform

in size and are univoltine. P. campestris is at least bi- and

perhaps typically trivoltine; it is also highly variable in size.

There is good evidence that the only host of P. fonsecai is

D. stylata, at least in southern England. P. campestris attacks

a whole spectrum of hosts, nine have been recorded from Silwood

Park. One may speculate that P. fonsecai evolved from P. campestris

(or its ancestor) by specialising its attack on a morphologically

distinctive leafhopper. It is significant that campestris has

not been recorded as a parasite of D. stylata. The two species may

be prevented from interbreeding by these biological differences,

including phenology of hosts.

One of the main aims at the outset of this study was to

investigate the life cycles of Pipunculidae, since even this basic information was not available. Adults were successfully sampled with a Malaise trap. As with any trapping method, there is the shortcoming that peak catches may reflect peak activity and susceptibility to capture rather than abundance in the field. A second means of sampling was with a hand net. The data on abundance obtained from the latter agreed with that of the Malaise trap.

What is perhaps more important is that observations on the times of emergence of the larvae from their hosts, togethet with the analyses of adult catches, enabled elucidation of the life histories of the most common species. It is hoped that the interpretations of pipunculid phenologies given in Section B are therefore valid.

In this study 18 species of Pipunculidae were bred out from

26 species of leafhoppers. Waloff (1975) has already shown that some of these species at Silwood Park have little host specificity. 166

Up to 1966 Coe (1966) collated the breeding records.of six of the pipunculid genera. The breeding records in this study have provided two exceptions to his suggestions. Cephalops (C. furcatus) is now known to select Cixiidae as well as Delphacidae and Verrallia

(V. setosa) is known to select Cicadellidae (Macropsinae) as well as

Cercopidae. That Cephalops attack the Fulgoromorpha exclusively seems to be the only valid broad generalisation. At the species level there is some evidence for strict host specificity.

C. curtifrons, P. fonsecai and P. zufmayeriae are species which attack taxonomically distinct leafhoppers at Silwood Park, the hosts being S. minutes, D. stylata and G. ventralis respectively.

The latter do not have any other species in their respective genera and both hosts and parasites are univoltine.

Another way of considering host specificity in this study has been to look at size variability of the adult parasites. In the four genera Cephalops, Pipunculus, Alloneura and Eudorylas, significant differences in the size of the flies result from larval development in differently sized hosts. This phenomenon is well known in other insect parasites (Salt 1941). A pipunculid attacking a wide range of host species can be expected to vary more in size than a pipunculid attacking one or only a few. Size variation of adult pipunculids collected in the field was quantified by calculation of the coefficient of variation based on measurements of wing length and head width. Statistical tests comparing the values of the coefficient of variation showed that there are often significant differences between species. It has been possible to explain some of the observed differences by regression analyses relating the coefficient of variation with the number of host species parasitised. 167

The regression analyses do not explain all the variation in size of the adult flies. Apart from errors in the recording of the number of host species parasitised, ensuing from the observation that the most common pipunculids will tend to be bred out more frequently and be recorded from a disproportionately large number of hosts, there may also be increase of variability associated with that of parasite abundance. Ford (1971) has shown how expanding animal populations become more variable, there being relaxation of some selection pressure and survival of atypical forms in the more favourable environments. One way this increased variability manifests itself in the Marsh Fritillary Butterfly studied by

Ford, was in size. Dissimilar distributions of suitable ranges of hosts may also account for some of the observed differences in size variability between pipunculid species.

Probability paper was used to plot wing length and head width distributions. It has been assumed that the observed frequency distributions of field collected flies, known to parasitise hosts of different sizes, represent the sum of separate and overlapping normal distributions, each corresponding to a different size of host. Separating these normal distributions by graphical methods, it is suggested that the principal host of the common pipunculid,

E. subterminalis at Silwood Park is as yet unknown; only a small part of this fly's size distribution can be explained by the sizes of hosts known so far.

Field observations on the oviposition behaviour of V. setosa demonstrate the great part played by vision in host location. The nymphs of Oncopsis flavicollis, the host of V. setosa, have "exploited" this dependence of the parasite on its vision by mimicking the birch buds and thus avoiding detection. 168

In Appendix C descriptions are given of male Pipunculidae collected near Stuttgart, West Germany. Nine species are described as new. These discoveries are indicative of the basic work still required on this poorly known family.

It is interesting that there is close agreement between adult and larval taxonomy in the Pipunculidae but not in the Syrphidae even though the two families are closely allied. A major revision of the higher classification of the Syrphidae was proposed by

Hartley (1961) on the basis of his studies on larval taxonomy.

They are saprophagous, phytophagous, or predacious, and a few are scavengers in the nests of social insects. The varied habits and structure of the larvae are reflected in Hartley's revised classification. The larvae of all Pipunculidae live inside the bodies of leafhoppers. Perhaps this uniformity of habit explains the close agreement between larval and adult taxonomy; evidently in the Syrphidae evolution of the larvae has proceeded independently from that of the adults. 169

SUMMARY

(1) Almost half of the 76 British species of Pipunculidae

have been found at Silwood Park and 18 species have been

bred out.

(2) Methods of rearing Pipunculidae from their leafhopper

hosts are described. The duration of the pupal stage at

20°C was recorded for both sexes of three species. In

each species the duration of the pupal stage was greater

in females than in males. This is discussed in relation

to emergence times of the adults.

(3) Many species of pipunculids show little host specificity. They may vary considerably in size intraspecifically, the

size depending on the species of leafhopper attacked; this

is reflected in measurements of wing length and head width.

(4) Coefficients of variations based on wing length and head width of field collected pipunculids often differ

significantly between species. This has been partly

attributed to differences in the number of host species

attacked, but other possible causal factors are considered.

(5) Using probability paper to plot distributions of wing length and head width of Pipunculidae, an attempt was made

to identify the importance of the host range in the biology

of the parasites. The implications of the differences in

shape of the distribution curves of the different pipunculid

species are discussed. Analyses of the distributions of

wing length frequency suggest that the principal host of

one of the most common species of Pipunculidae has yet to

be found. 170

(6) A key has been constructed for the identification

of the larvae of some of the 18 species of Pipunculidae

bred out. Characters used in the key include the structure

of the mouthparts and posterior spiracular plates. A

knowledge of the leafhopper host is often required to

identify larvae from the key. Scanning electron micrographs

are included to illustrate several characters referred to

in the key. Micrographs of the labial plates of some

species show probable sensory receptors.

(7) A Malaise trap was used in studies of the seasonal abundance of Pipunculidae. Observations on the times of

emergence of the larvae from their hosts, together with

analyses of the catches of adults in the Malaise trap,

elucidated the life histories of the most common species.

(8) Drawings of the male genitalia of most species of Pipunculidae at Silwood Park are given. The shape of

the male genitalia provides almost invariably absolute

characters for species identification.

(9) Field observations on the oviposition behaviour of

one species of Pipunculidae demonstrated the great part

played by vision in host location.

(10) There is good agreement between the larval and adult

taxonomy of the Pipunculidae. It is suggested this is

related to the uniformity of the larval habitat. 171

ACKNOWLFMGFaENTS

I should like to express my gratitude to Professor

T.R.E. Southwood for the provision of facilities at Imperial

College Field Station, Silwood Park, during the course of this work.

I wish particularly to thank my supervisor, Dr. N. Waloff, for her interest and encouragement and her critical guidance during the construction of this thesis.

I should also like to express my thanks to:

Mr. R.G. Davies for advice on statistical matters and for drawing my attention to some interesting papers;

Professor O.W. Richards for advice on scientific names;

The staff of the Entomology Department, British Museum

(Natural History) and the Hope Department of Entomology, Oxford, for allowing me access to the collections under their care;

Professor H. Rahmann of the University of Hohenheim, Stuttgart,

West Germany, for the provision of facilities during June and

July, 1974.

This study at Silwood Park was made while in receipt of a

Science Research Council Studentship. I gratefully acknowledge this financial assistance.

Lastly, I wish to thank the Deutscher Akademischer

Austauschdienst for their financial help which allowed me to study and collect in West Germany. This trip greatly benefited my work. 172

REFERENCES

ACZEL, M. (1948). Grundlagen einer Monographie der Dorylaiden (Dorylaiden-Studien 6). Acta zool. lilloana 6 : 5-168. BHATIA, M.L. (1939). Biology, morphology and anatomy of aphididophagous syrphid larvae. Parasitology : 78-129. CHANTER, D.O. (1965). The Malaise Trap. Ent. Rec. .71 : 224-226 CHAPMAN, R.F. (1969). The Insects Structure and Function. The English Universities Press Ltd., London. CLEMENTS, A.N. (1963). The physiology of mosquitoes. Pergamon Press, Oxford. COE, R.L. (1966). Diptera Pipunculidae. Handbk. Ident. Br. Insects 10 (2c). COE, R.L. (1967). Notes on British Pipunculidae (Diptera). Proc. R. Ent. Soc. Lond. : 181-2. COLLIN, J.E.-- 1945). Notes on some recent work on the Pipunculidae. Entomologist's Mon. Mag. 81 : 1-6. COLLIN, J.E. (1956). Scandinavian Pipunculidae. Opusc. Ent. 21 : 149-69. ESAKI, T. & HASHIMOTO, S. (1936). Report on the Leafhoppers injurious to the Rice Plant and their Natural Enemies [in Japanese] Pubis. ent. lab. De t. A ic. Y ushu Im . Univ. (for the year 1935 , 31 pp. Rev. appl. Ent. a 1936 : 465. FORD, E.B. (1971). Ecological genetics. Methuen, London. HARDING, J.P. (1949). The use of probability paper for the graphical analysis of polymodal frequency distributions. J. mar. biol. Soc. 28 : 141-53. HARDY, D.E. (1943). A Revision of Nearctic Dorilaidae (Pipunculidae). Kans. Univ. Sci. Bull. 22, pt.l, No.1 : 231 pp. HARTLEY, J.C. (1961). A taxonomic account of the larvae of some British Syrphidae. Proc. zool. Soc. Lond. 136 : 503-593. HARTLEY, J.C. (1965). The cephalopharyngeal apparatus of syrphid larvae and its relationship to other Diptera. Proc. zool. Soc. Lond. 141 : 261-280. JENKINSON, F. (1903). Verrallia aucta and its host. Entomolo gist's mon. Imo. : 222-3. KEILIN, D. (1944 . Respiratory systems and respiratory adaptations in larvae and pupae of Diptera. Parasitology .36: 1-66. KEILIN, D. & THOMPSON, W.R. (1915). Sur le cycle evolutif des Pipunculides, parasites intracoelomiques des Typhlocybes. C. r. Soc. Biol. Paris. /13 : 9-12. LE QUESNE, W.J. (1960). Hemiptera Fulgoromorpha in Handbk. Ident. Br. Insects, vol.II Part 3. London, R. ent. Soc. LEWONTIN, R.C. (1966). On the Measurement of Relative Variability. Syst. Zool. : 141-2. MAY, Y.Y. (1971). The biology and population ecology of Stenocranus minutus (Fabriclus) (Delphacidae-Bomoptera). PETD. Thesis, University of London. MICKEL, C.E. (1924). An analysis of a bimodal variation in size of the parasite. Dasymutilla bioculata Cresson. Ent. News, 35s 236-42. MYERS, J.H. & KREBS, J.K. (1974). Scientific American. PERKINS, R.C.L. (1905). Leaf-Hoppers and their Natural Enemies (Pt.4 Pipunculidae). Re ort of work of Ex eriment Station of Hawaiian Sugar Planters' Assoc., Bull. 1 4 : 123-57. 173

ROTHSCHILD, G.H.L. (1964). The biology of Pipunculus semifumosus (Kowarz) (Diptera Pipunculidae), a parasite of Delphacidae (Homoptera) with observations on the effects of parasitism on the host. Parasitology, at 763-769. SACK, P. (1935). Dorylaidae (Pipunculidae). In. Lindner, E., Flieg. Palaearkt. Reg. A (4), no. 32. 57 pp. Stuttgart. SALT, T. (1941). The effects of hosts upon their insect parasites. Biol. Rev. 16 : 239-64. WALOFF, N. (1973). Dispersal by flight of leafhoppers (Auchenorrhyncha, Homoptera). J. aptil. Ecol. 10 : 705-30. WALOFF, N. (1975). The parasitoids of the nymphs and adults of Leafhoppers (Auchenorrhyncha, Homoptera) of acidic grassland. Trans. R. ent. Soc. Lond. in press WALOFF, N. & SOLOMON, M.G. (1973). Leafhoppers (Auchenorrhyncha : Homoptera) of acidic grasslands. J. a 1. Ecol. 10 : 189-212. WHITTAKER, J.B. (1969). The biology of Pipunculidae Dipters7 parasitising some British Cercopidae (Homoptera). Proc. R. ent. Soc. Lond. A. : 17-24. WILLIAMS, F.T.7918). Some observations on Pipunculus, a fly which parasitises the cane leafhopper, at Pahala, Hawaii, February 11 - April 25, 1918. Hawaii. Plant. Rec. 1.1 (3) : 189-92. WILLIAMS, J.R. (1957). The Sugar-cane Delphacidae and their natural enemies in Mauritius. Trans. R. Ent. Soc—Lond. : 65-110. 174

APPENDIX A

TABLE 4 (Continued from p.10)

SIGNIFICANCE OF THE DIFFERENCE IN SIZE BETWEEN ADULT PIPUNCULIDAE BRED FROM DIFFERENT HOSTS

Mean wing Host length t P Pipunculus cam estrisd'V

E. obsoletus 54.37 1.138 0.5

D. abdominalis 48.08 3.164 0.01

Pipunculus campestris

D. abdominalis 48.90 1.007 0.5

E. obsoletus 58.05 3.189 0.01

E.sulphurella 51.57 1.177 0.2

Alloneura sylvatica

E. ocellaris 30.38 0.05

J. pseudocellaris 28.23 2.076 -0.2

Eudorylas subterminalisdV

E. ocellaris A? 40.42 1.028 0.5

P. confinis dV 38.02 28.691 0.01

E. ocellaris &W? 40.46 0.5

D. abdominalis 40.27 0.5

40.27 D. abdominalis 1 0.5

175

TAW? 4 (Contd.) • Mean wing Host length

Eudorylas subterminalis 6V

J. pseudocellaris 38.71 8.211 0.01

J. pseudocellaris 38.71 6.514 0.02

Mean head Host width

Eudorylas subterminalisgle

E. ocellaris45 1 54.17 1.024 0.5

Note: No distinction is made in the above table

between macropterous and brachypterous

Delphacidae.

176

APPENDIX B

TABLE 8 (Continued from p.27)

COMPARISONS OF THE COEFFICIENTS OF VARIATION USED IN PLOTTING FIG. 1(11

Species of Parasite C.V. F P

/ E. obl!uus 5.59057 31.25447 1.07925 0.25

8 CC. semifumosus 5.38140 28.95951 1.160594 0.25

28.95951 11 C. semifumosus 5.38140 10.47788 0.001

5.59057 31.25447 12 E. obliquus 1.25257 0.1

12 E. obliquus 5.59057 31.25447 1.64148 0.025

1, E. obliquus 5.59057 31.25447 2.32533 P<0.001 m. E. fascipes 3.66618 13.44088

15 E. obliques 5.59057 31.25447 1.30822 0.001

A. sylvatica 4.99523 24.95232 16 1.31049 0.10

17 A. sylvatica 4.99523 24.95232 1.85645 P<0.001 I E. fascipes 3.66618 13.44088 24.95232 A. sylvatica 4.99523 9.02803 0.005

19.04039 20 E obscurus 4.36353 6.88903 0.01

E fascipes 3.66618 13.44088 4.86306 0.025

TABLE 8 (Contd.)

Species of Parasite c.v.

A sylvatica 22 ' 4.99523 24.95232 1.21624 0.10

25 C. curtifrons 3.62730 13 .15730 4.76040 0.025

APPENDIX C

During the summer of 1974 a large collection of Pipunculidae was made in Plattenhardt, (nr. Stuttgart). This collecting trip to West Germany was made possible by a scholarship awarded by the

Deutscher Akademischer Austauschdienst, which I gratefully acknowledge.

Forty-four species were collected and nine of these are described as new. A list of the species is as follows:-

CHALARINAE CHALARUS Walker spurius Fallen basalis Loew griseus Coe pughi Coe VERRALLIA Mik aucta Fallen

PIPUNCULINAE ALLONEURA Rondani sylvatica Meigen cilitarsis Strobl palliditarsis Collin nigritula Zetterstedt DORYLOMORPHA Aczel confusa Verrall xanthopus Thomson xanthocerus Kowarz PIPUNCULUS Latreille * zugmayeriae Kowarz campestris Latreille oldenbergi Collin thomsoni Becker sp. indet. CEPHALOPS Fallen aeneus Fallen oberon Coe subultimus Collin semifumosus Kowarz ultimus Becker carinatus Verrall

collected in Ellern 179

EUDORYLAS Aczel horridus Becker barbarus sp. n. subterminalis Collin terminalis Thomson obliquus Coe fascipes Zetterstedt obscures Coe longifrons Coe montium Becker fuscipes Zetterstedt zonatinus sp. n. zonellus Collin leptomeros sp. n. pachymeros sp. n. elephas Becker subelephas sp. n. mastodon sp. n. moehringensis sp. n. ruralis Meigen fusculus Zetterstedt minutulus sp. n. gynandroides sp. n.

DESCRIPTIONS OF PIPUNCULINAE FROM PLATTENHARDT, W. GERMANY

The following descriptions apply mainly to the males unless otherwise stated. Particular emphasis has again been placed on the

male genital structures in separating species. The wing lengths given are from the humeral cross-vein to the wing tip and all refer to males.

PIPUNCULUS Latreille

P. oldenbergi Collin

This species belongs to the same group as zugmayeriae

and spinipes, i.e. its aedeagus is bifurcated and reunited

at tip (fig. 94(f)). It is most closely allied to spinipes.

Male Frontal triangle longer than in spinipes, distance between upper point of frontal triangle and hind margin of ocellar triangle about equal in length to frontal triangle. Maximum length of third antennal segment about one and a half times the maximum breadth of the second; in spinipes it is twice as long as the maximum breadth 180

of the second. The base of the arista more dilated in oldenbergi than in spinipes. Thorax brownish dusted for anterior half, posterior quarter and base of scutellum. The thorax is not so extensively dusted as in spinipes. Humeri dark. Halteres yellow with brownish head. Femora black with knees broadly yellow. Basal third to half

of tibiae yellow (most distinctly so dorsally). Tergum 1 of abdomen

greyish dusted; basal half of tergum 2 and basal quarter or less of terga 3 and 4 brownish dusted. Sides of terga 2-5 conspicuously

.greyish dusted. Eighth abdominal segment with apical membranous area larger than in spinipes; in ventral view, claspers incurved at tips (fig. 116) (scarcely incurved in spinipes (fig. 95)); in lateral view, claspers much less strongly curved in oldenbergi (fig. 116(e)), than in spinipes (fig. 95(e)). Sperm pump apodeme similar to that in spinipes (fig. 116(a)).

Wing length 4.964-5.201 mm; mean 5.095 mm. Based on 6 males collected at Plattenhardt, W. Germany, in July, 1974.

Female Anterior third or more of thorax greyish dusted (not brownish dusted as in male). Leg colour as in male. Abdomen with tergum 1 and basal half of tergum 2 grey dusted. Ovipositor with piercer obviously downcurved (fig. 134). P. oldenbergi has the greatest wing length of all species

of Pipunculidae that were measured. The specimens collected

were identified as oldenbergi on the basis of Collin's

description (1956). A pair in copula of this species was

taken and the female ovipositor (fig. 134) differs considerably

from that of spinipes, where the piercer is only slightly down-

curved. In P. varipes Meigen the piercer is even more downcurved

than in oldenbergi. P. varipes may be further distinguished

from oldenbergi by its yellow femora. 181

EUDORYLAS Acz4l

E. horridus Becker and E. barbarus sp. n.

Legs black apart from knees and basal dorsal third of tibiae.

Posteroventral spur present on anterior tibiae. Costal stigma

complete; third costal segment longer than the fourth. These

two species are considered together as the male genitalia are

similar (figs. 117 and 118).

E. horridus Becker

Male Humeri yellow. Middle of hind tibiae with two (sometimes

one) short anterior bristles. Abdominal terga covered with black

bristly hairs. Viewed from behind, terga with entire (tergum 1) or

interrupted (terga 2-5) silvery grey bands on posterior margins of

segments. The band is broadest on tergum 5 where it is at least half

the length of the tergum. Claspers hook-like (fig. 117) with whitish

yellow tips. Sperm pump apodeme as in fig. 117(a). Aedeagus three-

forked but shorter than in barbarus.

Female Ovipositor base small without a dorsal longitudinal groove.

Piercer twice as long as base and slightly upcurved.

'8 males and 2 females were collected during the first two weeks of

August, 1974, at Plattenhardt, W. Germany.

Wing length 3.223-3.738 mm; mean 3.565 mm. Based on the 8 males.

E. barbarus sp. n.

Male Humeri yellow. No anterior bristle(s) at middle of hind tibiae.

Thorax and abdomen of a uniform matt black colour. Abdominal terga

with some bristly hairs but weaker and much less numerous than in

horridus although more obvious than in other Eudorylas species. The

claspers are much stouter than in horridus and less outwardly curved

(fig. 118). The aedeagus is about as long as in obscurus (fig. 88(b))

but not coiled. The sperm pump apodeme is similar to that of horridus. 182

2 males were collected on 14 and 30 July, 1974, at Plattenhardt,

W. Germany.

Wing lengths 3.500 and 3.540 mm.

E. barbarus may readily be distinguished from

horridus by the absence of silvery grey abdominal bands

and by the absence of numerous abdominal bristles. The

differences in the male genitalia can be seen in alcoholic

or potashed material.

E. terminalis Thomson

This species has the general characters of the

Group I species in Section E. It is most closely

allied to subterminalis.

Male Abdominal segment 8 with'small apical membranous area. When

seen from behind, hypopygium as broad as the fifth abdominal tergum

and much wider than deep. In subterminalis the hypopygium is

considerably narrower than tergum 5 and about as wide as deep. The

claspers of the two species are differently shaped (figs. 86 and 119).

Aedeagus with terminal three-forked filamentous portion longer than in

subterminalis. Sixth abdominal tergum (i.e. the part of the tergum

which has been displaced ventrally) with a wart-like protuberance

which is slightly curved over (fig. 119). In subterminalis this

structure is represented by a distinct hook (fig. 86). E. terminalis

is a larger species than subterminalis. • Wing length 3.382-3.797 mm; mean 3.616 mm. Based on 6 males

collected on 30 July and 1 August, 1974, at Plattenhardt, W. Germany.

B. zonatinus sp. n.

The male genitalia are similar to those of zermattensis

Becker. The humeri are black, whereas in zermattensis they

are yellow. The species keys to zonatus Zetterstedt in

Sack's key (1935). 183

Male Antennae black with short pointed tip. Legs black except

for yellow knees. Stigma complete; third and fourth costal segments

about equal. Humeri black. Thorax and abdomen of a matt black

colour. Apical membranous area of eighth abdominal segment larger

and more ventrally directed than in zermattensis. Sperm pump apodeme

more or less as in obscurus (fig. 88(a)). Aedeagus as in fig. 120(b).

The right claFper has the inner apical margin with an obvious "beak".

The latter is not present in zermattensis (fig. 89).

Wing length 3.105-3.480 mm; mean 3.276 mm. Based on 6 males collected on 30 July and 3 August, 1974, at Plattenhardt, W. Germany. Apart from the differences in the male genitalia and

overall size, the males of zonatinus resemble those of zonatus

and zonellus. The apical membranous area is more oblong than

in the latter two. E. zonatinus sp. n. may prove to be Collin's

E. inferus (1956). It has not been possible to examine the

male genitalia of this species as yet.

E. leptomeros sp. n. and E. pachymeros sp. n.

These two species share the same group characters as

subterminalis (Section E), i.e. four anterior tibiae with a

distinct posteroventral spur at tip; humeri yellow; bases

of femoradistinctly yellow; costal stigma complete; eighth

abdominal segment of male with membranous area. They are

considered together because the membranous area is very

small in both species.

E. pachymeros sp. n.

Male Antennae brownish, long pointed. Humeri yellow. Halteres yellow with brownish head. Fore and mid tibiae with a posteroventral spur at tip. Femora strong, especially the hind pair; black apart from yellow base and tip. Tibiae yellow with apical ventral half

brownish (less so on hind tibiae). Tarsi yellow apart from last 184

tarsal segment. Stigma complete; third and fourth costal segments

about equal. Abdominal segment 8 with very small, round apical

membranous area. Claspers and aedeagus as in fig. 121. Sperm

pump apodeme resembling that of fascipes (fig. 83(a).

Wing length 4.192-4.509 mm; mean 4.346 mm. Based on 9 males collected on 1 and 15 August, 1974, at Plattenhardt, W. Germany.

E. leptomeros sp. n.

Male Pitting general description of pachymeros except smaller;

femora more slender; three-forked terminal filament of aedeagus much

shorter; hypopygium relatively smaller; claspers very differently

shaped (fig. 122) and both are equally distant from the ventral

abdominal. well (in pachymeros the left clasper is closer to the ventral

abdominal wall than is the right). Sperm pump apodeme with less vs rounded head than in pachymeros. Wing lengths of four males collected on 15 August, 1974, at

Plattenhardt, W. Germany: 3.916, 3.955, 3.876 and 3.836 mm.

The two species are readily distinguished by the

difference in size, strength of the femora and shape of

the claspers.

E. elephas Becker and E. subelephas sp. n.

Both species with hind margins of abdominal terga 2-5

membranous to varying degrees (fig. 132) so that the length

• of the terga is much less on the disc than at the margins; this is most obvious in potashed material. The sixth

abdominal sternum has one(elephas)or two (subelephas) ventrally

directed projections.

E. elephas Becker

Male Third antennal segment yellow, long pointed. Humeri yellow.

Halteres yellow with somewhat brownish head. Stigma complete; third

costal segment longer than fourth. Fore and mid tibiae with postero- 185

ventral spur at tip. Legs yellow apart from broadly dark ringed

hind femora, broadly but incompletely dark ringed fore and mid femora

and apical tarsal segments. Abdomen with terga partly membranous

(fig. 132). Hypopygium very large, when seen from above in specimens

in alcohol, as long as or almost as long as segments 3, 4 and 5.

Dried specimens tend to have the long axis of the hypopygium inclined

to that of the preabdomen. Sixth abdominal sternum with an obvious

ventrally directed but curved, pointed projection (fig. 123) which is

most obvious when the abdomen is viewed from the side. Aedeagus very long and coiled, when uncoiled about as long as dorsal length of

abdomen. Sperm pump apodeme of same general shape as in fascipes

(fig. 83(a)) but less rounded.

Wing length 3.935-4.390 mm; mean 4.140 mm. Based on 6 males collected during July 1974, at.Plattenhardt, W. Germany.

E. subelephas sp. n.

Male Fitting general description of elephas except smaller; third and fourth costal segments about equal; sixth abdominal sternum with two ventrally directed projections, hypopygium relatively smaller

(in dorsal view in specimens in alcohol, shorter than combined length of terga 4 and 5); apical membranous area much smaller; aedeagus shorter (about one third of dorsal length of abdomen); claspers differently shaped (fig. 124). Wing length of a single male collected on 4 July, 1974, at Plattenhardt,

W. Germany: 3.836 mm.

E. mastodon sp. n. and E. moehrin ensis sp. n.

Both species have the abdominal terga 3 and 4 with the

posterior margin membranous so that the length of the terga is

greater at the lateral margins than on the disc. The

membranous area is not nearly so extensive and conspicuous,

however, as in elephas and subelephas; as in the latter two 186

species this character is best seen in potashed material.

There are no conspicuous, pointed, ventrally directed

projections on the sixth abdominal sternum as in elephas

and subelephas.

E. moehringensis sp. n.

Male Third antennal segment yellowish and long pointed.

Humeri yellow. Halteres yellowish. Posteroventral spur present

on fore and mid tibiae. Legs yellow apart from darkened apical

tarsal segments and femora which are broadly darkened dorsally.

Costal stigma complete; third and fourth costal segments about

equal. Sixth abdominal sternum with very small, inconspicuous,

truncate, ventrally directed projection (fig. 125). Aedeagus very

long and coiled. Sperm pump apodeme resembling that of asc1222

(fig. 83(a)). Claspers as in fig. 125. • Wing length of 2 males collected on 1 and 15 August, 1974, at

Plattenhardt, W. Germany: 3.480 and 3.362 mm.

E. mastodon sp. n.

Male Third antennal segment yellowish but broader and not so long

pointed as in moehringensis, elephas or subelephas. Humeri yellow.

Halteres yellow with brownish head. Four anterior tibiae with

distinct posteroventral spur at tip. Costal stigma complete; third

and fourth costal segments about equal. Legs with all femora broadly

and completely dark ringed. Fore and mid tibiae darkened on apical • half ventrally. Hypopygium about as long as tergum 5. Aedeagus

very long and coiled as in elephas. Claspers as in fig. 126.

Wing length 3.757-4.153 mm; mean 3.922 mm. Based on 9 males collected on 30 July, 1 and 15 August, 1974, at Plattenhardt, W. Germany. 187

E. ruralis Meigen, E. fusculus Zetterstedt, E. minutulus sp. n., E. gynandroides sp. n.

Male abdominal segment 8 with no apical membranous area. Costal

stigma at least slightly abbreviated. The four species may be

further separated into two groups : gynandroides and ruralis with

yellow humeri, minutulus and fusculus with black humeri.

E. gynandroides sp. n.

Male Antennae brownish. Humeri yellow. Halteres yellow. Legs

with femora black except at base and tip. Fore and mid tibiae

darkened for apical half ventrally; hind tibiae narrowly dark ringed

about centre. Apical tarsal segments darkened. Fore and mid tibiae

with posteroventral spur at tip. Costal stigma incomplete; third

costal segment clear for about its basal fifth. Third and fourth

costal segments almost equal. Abdominal segment 8 with no apical

membranous area. Hypopygium very large and bulbous with a conspicuous

ventral projection (figs. 127 and 133). Sperm pump apodeme large and

elaborate, occupying most of the seventh and eighth segments, possessing

apodemes and ridges.

Wing length of 2 males collected on 27 June, 1974, at Plattenhardt,

W. Germany: 3.955 mm. each.

E. ruralis Meigen

Male Antennae blackish brown, third segment narrower than in

Halteres • gynandroides, moderately long pointed. Humeri yellow. blackish. Legs black apart from yellow knees and about basal half

of tibiae. Costal stigma abbreviated, basal quarter clear; third

and fourth costal segments about equal. Eighth abdominal segment

without apical membranous area. Hypopygium (particularly eighth

segment) very large and bulbous. Sperm pump apodeme elaborately

constructed as in gynandroides. Claspers as in fig. 128. 188

Wing length of single male collected on 30 July, 1974, at

Plattenhardt, W. Germany: 2.848 mm.'

The common possession by the above two species of

enlarged and rounded seventh and eighth segments containing

large and complex sperm pumps suggests a close affinity

between them. They may readily be distinguished by size,

clasper shape and the ventral projection on segment 8 in 11) 2E2=c._.1a3 ..;:ie2.-1 •

E. minutulus sp. n.

Male Antennae black, short pointed (noticeably so in comparison

with fusculus). Humeri black. Halteres black. Legs black apart

from very narrowly yellow knees. Costal stigma incomplete, occupYing -

only apical two thirds of the third costal segment. Third and fourth

costal segments about equal. Eighth abdominal segment without an

apical membranous area. Claspers as in fig. 129. Sperm pump

apodeme very small and rod shaped.

Wing length of single male collected in July, 1974, at Plattenhardt,

W. Germany: 2.630 mm.

This species is the smallest of the group without an

apical membranous area. The general description fits that

of furvulus Collin (Collin 1956) except that middle cross-vein

is not opposite the base of the stigma and the drawing of the

'male hypopygium in lateral view does not agree with that of

minutulus. It should be added that Collin's drawing was

probably made from a dried specimen. I am describing this

species as new. 189

E. fusculus Zetterstedt

Male Fitting general description of minutulus except larger;

third costal segment shorter than fourth; knees more broadly

yellow; sperm pump apodeme not rod shaped but larger and of

same general shape as in horridus (fig. 117(a)); claspers very

differently shaped (fig. 130). The aedeagus is straight and

extends anteriorly almost to the middle of the claspers; it is,

as usual, three-forked.

Wing length of 3 males collected in July, 1974, at Plattenhardt,

W. Germany : 2.887, 3.164 and 3.164 mm.

111 Explanation of Figs. 116-134

Figs. 116-131 - Male Postabdomen in Ventral View

Fig. 116 P. oldenbergi 117 E. horridus 118 E. barbarus 119 E. terminalis 120 E. zonatinus 121 E. pachymeros 122 E. leptomeros 123 E. elephas 124 E. subelephas 125 E. moehringensis 126 E. mastodon 127 E. gynandroides 128 E. ruralis 129 E. minutulus 130 E. fusculus 131 C. carinatus

Fig. 132 - E. elephas, male abdomen in dorsal view

Fig. 133 - E. gynandroides, male postabdomen in lateral view

Fig. 134 - P. oldenbergi, female ovipositor in lateral view

a = sperm pump apodeme b aedeagus in lateral view e = right clasper in lateral view

Scale line = 0.5 mm.

CD

RS

• 191

a - - - - 194

b

..n

f 196

b

1 As. • st WO. 0 -- 0 0 0.1

9 201 202

• 203 204

i 205

r

r. 206

132

•.

1, 1 207

1 / / ///// / / /1/1 / // / '/'1 ‘7,,l /( ',//// // // 11// /1 /// ll• 1 ( , , / '/ // / / I / // / 0/1 / l/l i t , / / d i 1 1/ 11 / 1 , / % / /" /I ///0/,'/ /11 ,/ /1,1