The parasitoid complex of tedella (Cl.) (: ) MIKAEL MONSTER-SWENDSEN

Miinster-Swendsen, M.: The parasitoid complex of Epinotia tedella (Cl.) (Lepidoptera: Tor­ tricidae). Ent. Meddr, 47:63-71. Copenhagen, Denmark 1979. ISSN 0013-8851. The parasitoid species attacking Epinotia tedel/a (Cl.) in North Zealand, Denmark, have been studied during nine years. Pimplopterus dubius (Hgn.) and Apanteles tedel/ae Nix. were the dominant primary parasitoids. Campoplex cursitans (Hgn.) and Exochus tibialis Hgn. were both cleptoparasitoids associated with A. tedel/ae and P. dubius, respectively, whereas Mesa­ chorus si/varum Curt. was the only hyperparasitoid, which attacked all of the above men­ tioned parasitoids. Summarized data on phenology and biology of the species are presented in the paper. P. dubius and A. tedellae cannot discriminate between parasitized/unparasitized hosts, leading to random super- and multiparasitism, but the distributions in time and space of their attacks are not identical. Means and ranges of parasitism found in different stands and years are presented, as well as a general scheme on the outcome of the multiparasitic competition. Mikael Miinster-Swendsen, Institut for almen Zoologi, Universitetsparken 15, DK-2100 Kpbenhavn 0, Danmark.

Introduction The needleminer, Epinotia tedella (Cl.), is forest floor. Pupation takes place in May and a well known pest on Norway Spruce (Pi­ the pupal period lasts 3-4 weeks. cea abies Karst.) throughout Europe. In mid-August, host larvae were collected Over a period of nine years (1970-1978), the from branch samples and dissected in the lab­ population dynamics of E. tedella has been oratory. At this time of the year all parasitoid studied in a stand of Norway Spruce (treeage: attacks on E. tedella had occurred and it was 34 years in 1978) in the forest Gribskov, North then possible to detect the degree of super­ Zealand in Denmark. During the study it be­ parasitism, multiparasitism and encapsulation came apparent that parasitoids significantly af­ and to trace the outcome of any kind of com­ fect the population dynamics of E. tedella. petition among the parasitoid larvae (Miin­ The present paper summarizes the data on ster-Swendsen, 1973a), though the host phenology and relative importance of the indi­ was only about 2 mm long and had to be dis­ vidual parasitoid species and their associated sected with fine insect-pins. clepto- and hyperparasitoids, and describes the When the host larvae spun down from the interspecific relations and the competitive as­ canopy in November and December, they were pects related to multiparasitism. sampled in 200 funnel traps. These were at­ tended every week and the larvae caught were immediately counted and dissected. Host biology and collecting of data In May, host and parasitoid mortalities were E. tedella emerges from the forest floor in June. assessed from host cocoons sampled from the The female deposits her eggs singly on the forest floor. needles in the canopy, where the first larval in­ In June and July, 200 emergence traps of a star appears in July. The larva mines in the type described by Miinster-Swendsen (1973b) needles until November, when it spins down were placed on the forest floor for sampling of from the canopy to hibernate in a cocoon in the the emerging host and parasitoid populations.

63 The trap glasses were attended every week and whether any of the larval endo-parasitoids of E. hosts and parasitoids were identified, counted tedella could be found. No such overlap was ob­ and sexed. served except for one incident, where a larva The abundance of hosts and parasitoids in dif­ identical with that of A.? dngulipes was found in ferent spruce stands was studied by taking E. nanana, whereas an Agathis-species frequent­ branch samples from stands of varying ages in 8 ly found in P. clausthaliana was surely not identi­ different forests in North Zealand in 1971, and cal with that in E. tedel/a. by the use of trap funnels in different stands in Thus, at least P. dubius and A. tedel/ae can be Gribskov forest in 1977 and 1978. regarded as strongly host-specific in a pure spruce stand. A. tedellae is described as genuine­ ly host-specific by Capek (1969), whereas P. du­ Parasitoid species bius, though well adapted to E. tede/la, has been In North Zealand the following parasitoid spe­ recorded from other host species, according to cies were found on E. tede/la through investiga­ Thompson (1957). This might be due to confu­ tions of about 10,000 host individuals: sion concerning the identification and taxonomy of the parasitoids (Capek, 1969). Hymenoptera Ichneumonidae: All the Ichneumonidae and Braconidae Pimplopterus (Lissonota) dubius (Hgn.) found on E. tedella are monovoltine and solitary Mesochorus si/varum Curt. endo-parasitoids, attacking the host in its first Campop/ex cursitans (Hgn.) or second larval instar. Parasitoids attacking Exochus tibialis Hgn. the pupal stage have neither been found in the Braconidae: present study nor in other studies on E. tede/la. Apante/es tede/lae Nix. Agathis? dngulipes Nees. Tetracampidae: 1. Pimplopterus dub ius (Hgn.) Dipriocampe sp. The species is a primary parasitoid attacking Trichogrammidae: the first larval instar (L 1) of E. tedel/a from late Trichogramma evanescens Westw. June till the end of July. The adults emerge be­ tween 10 June and 15 July with a protandry of Diptera Tachinidae: about 10 days. The sex-ratio of different gener­ Unidentified larvae. ations varies and <;?!Q-ratios between 0.66 and Parasitoids known, or assumed to be associated 2.73 (mean and S. E.: 1.67 ± 0.27) have been ob­ with E. tedel/a in Austria and Germany have served during eight years within a single spruce earlier been recorded (Schedl, 1951; Fiihrer, stand. the individual female probably spends 1964), but in most cases the findings were based some days swarming and mating before search­ on the use of emergence-traps and -boxes, a ing and oviposition is commenced. She follows a method that often leaves a great deal of uncer­ particular behavioural sequence during the de­ tainty with respect to the true host species of tection and parasitation of the host: When the the collected parasitoid and gives no informa­ female finds the small pile of faecal pellets fixed tion on the relationships between the parasitoid by the host larva outside the entrance to the species. Further, these investigations were mine, she investigates the pile closely by intense carried out during outbreaks of E. tedel/a, palpations by the antennae. She then liberates whereby unusual parasitoid abundance might the fine, 6 mm long ovipositor from the valvae, have appeared. The species composition found leads it through the entrance of the mine, by Fiihrer (1964) in Schleswig-Holstein is very moves a little to let the ovipositor follow the close to that found in the present investigation. mine, and remains quiet for a moment, appar­ Epinotia nanana Tr. and Pseudohermenias claus­ ently depositing the egg. After withdrawal of thaliana (Sax.) both live on Norway Spruce and the ovipositor, she cleans it with her hind legs have a biology similar to that of E. tedel/a, but and brings it in position between the valvae they were both less abundant than E. tedel/a, again. This sequence is followed by intense which was the predominant lepidopteran spe­ cleaning of the whole body and especially of the cies in all stands. The parasitoids of the former antennae. The total »handling time« (Holling, two species were studied in order to observe 1959) lasted between 40 and 120 seconds in the

64 a a 1mm

0.5mm 0.2mm

k

1mm 1mm

d

e

1mm 1mm

g 0 0.1mm

n

1mm 1mm

Fig. I. Egg and larvae of larval endoparasitoids from E. tedella. P. dubius (a-e), eggchorion (a), early L1 (b), L2 (c),

head of L, (d) and head of L, (e). E. tibialis (f-g), late L1 (!)and early L1 (g). A. tedellae (h-k), early L1 (h), head of L1,

ventral view (i), late L1, lateral view U) and dorsal view (k). C. cursitans, L1 (I). A.? cingulipes, late L1 (m). M. si/varum

(n-o), early L1 lateral view (n) and head, ventral view (o).

laboratory, where all these observations took protected against attacks. This short-time sus­ place. ceptibility of the host results in synchronization A host larva placed outside a mine was not aspects of importance in the dynamics of the noticed by the searching parasitoid and never species (Miinster-Swendsen & Nachman, 1978). released an oviposition behaviour; in addition, The egg is deposited in the haemolymph of it was observed that host larvae in mines longer the host and can be found in various places than 6 mm could not be reached by P. dubius. within the host body during the next 5 days. The To produce a 6-7 mm long mine only takes the newly hatched parasitoid larva is mainly found newly emerged larva 3-5 days after which it is in the anterior part of the host, whereas the

65 older larva is found in the posterior part (Jpr­ the results fit a Poisson-series (Fig. 2a), corre­ gensen, 1975). According to Jprgensen, these sponding to an apparent random search for changing positions play a role in the intra- and hosts, combined with complete absence of dis­ interspecific competition between parasitoid crimination ability. However, a Poisson-series larvae. could have appeared if search was not random, P. dubius has five larval instars some of which or, for other reasons, all hosts did not have the are shown in Fig. 1 b-e. The first ecdysis takes same chance of being found and attacked, and if place about I October and often coincides with a certain degree of discrimination was present. an ecdysis of the host. P. dubius hibernates as L2 Generally, the defence mechanism of the host within the host in the forest floor, and not until is ineffective against the well adapted P. dubius, ultimo April does it continue its development but a few parasitoid larvae are nevertheless en­ and eats the host larva. L~ leaves the fragile inte­ capsulated by haemocytes. Thus, out of 317 gument of the dead host, and, within the host co­ single eggs or larvae 10 eggs and 4 larvae were coon, it spins a light cocoon, which darkens at encapsulated. the rear end due to ejection of the larval me­ The presence of the small P. dubius larva pro­ conium. The pupal stage lasts about one month. vokes some changes in the host, as the develop­ The female of P. dubius is not capable of ment of gonads and wing buds are suppressed avoiding already parasitized hosts and super­ (Fiihrer, 1972, 1973); further, the time at which parasitism followed by intraspecific competition the host leaves the canopy is delayed. among the larvae is frequently found. In the case of superparasitism only one parasitoid 2. Apanteles tedellae Nix. larva, usually the oldest and biggest, survives This primary parasitoid attacked L1 and L2 while the other larvae in the host are suppres­ from the beginning of July till the beginning of sed physiologically and sooner or later die. This August. The adults emerged between 15 June suppression is often followed by encapsulation and 15 July with a protandry of about 9 days. by haemocytes of the host.

(a) OE (b) 542 obs. 800 1021 obs. OE 350 P>.9 .5

Ill OE u; 150 150 0 .&: -0 olOo 100 c:

50 50 OE OE . !l g;_, OE m. OE OE 0 2 3 4 0 2 3 4 Fig. 2. Observed (0) and expected (E) numbers of E. tedella containing 0-4 parasitoids in their body. The expected numbers refer to a Poisson-series. P. dub ius (a), and A. tedellae (b).

66 nance was only observed in one year (1975), with a protandry of about one week. The while the other years showed an excess of fe­ <;?/0-ratio varied between 0.44 and 0.67. The egg males. Little is known about the behaviour of is deposited in the haemolymph of the parasitoid the adult A. tedellae, except that the female may larva located within E. tedella, and is found at oviposit in the host larva simply by penetrating different places within the body. The number of the mine wall with her 1 mm long ovipositor. larval stages is not known, but M. si/varum hi­

This behaviour creates no synchronization bernates as a small L1 (Fig. I n-o) within the still problems. living parasitoid. The egg and larva (Fig. lh-k) are found in the Superparasitism occurs and up to three haemolymph within the abdomen of the host. larvae have been found in a single P. dubius Three larval stages exist and A. tedellae hiber­ larva. In that case only one was alive while the nates as L1 within the host. After leaving the others had been suppressed or directly killed dead host in May, L3 spins a cocoon and pupates and appeared small and sleazy. An egg of M. sil­ within the host cocoon. The cocoon of A. tedel­ varum was once found free in the haemolymph lae is a little shorter than that of P. dubius, and is of an E. tedella which did not contain any other covered by a few light-brown threads. parasitoid, but the egg had not hatched, though A. tedellae is not capable of avoiding super­ it was found on 10 November. On a few occa­ parasitism, and the first larva to arrive will at­ sions solitary eggs of M. si/varum have been tack another egg or larva of its own species, found encapsulated by haemocytes and thus de­ and of other species. It bites the competitor, stroyed in both P. dubius and A. tedellae. keeping the mandibles in its body for some time, Hyperparasitism of the rather transparent L1 of a situation often found during the dissections. A. tedellae can be detected directly under suit­ Finally, the damaged larva is killed by encapsul­ able light conditions in the microscope, whereas ation of host haemocytes. the larvae of P. dubius have to be dissected to as­ The spatial distribution of attacks on hosts certain whether they are hyperparasitized; the was found to be contagious, and hence, a ran­ parasitized parasitoid larva is often smaller and dom distribution of eggs and larvae among has a "humpback-like" appearance and is ap­ hosts, i. e. a Poisson-series, would not appear if parently somewhat weakened, as the lepidopte­ discrimination between parasitized/unparasi­ ran host is less affected by its presence than tized hosts was totally absent. Samples from usual. branch sections at one particular canopy-height showed a distribution that followed a Poisson­ 4. Campop/ex cursitans (Hgn.) series (Fig. 2b) when sampling was performed with a view to eliminate the effect of spatial dis­ Close investigations through all years have tribution. The results may thus be interpreted shown that C. cursitans is an obligate clepto­ as a local random search on branches. In other parasitoid, as it does not attack unparasitized words, the search in great scale is aggregated, larvae of E. tedella, but only those that have but the species has no capability of discrimina­ been parasitized specifically by A. tedellae. tion. However, on very few occasions, it has been No sol,itary A. tedellae larva has ever been found together with A.? cingulipes, P. dubius and found encapsulated within the host, emphasi­ E. tibialis. The adults emerged during the zing the good adaptation to the host species. The period 20 June - 25 July, with a protandry of effect on the host is also more pronounced than about 8 days, and <;?/0-ratios between .64 and that of P. dubius. In addition to the suppression .87. of gonads and wing buds, larval colours do not The first instar larva (Fig. 11 is found in the develop and the size and weight of the host de­ haemolymph in the thoracic region of the larva crease appreciably (Fiihrer, 1970, 1972, 1973). of E. tedella. C. cursitans hibernates as L1 and completes its development during May and June

at the expense of the host. L1 has only rudimen­ 3. Mesochorus si/varum Curt. tary mandibles and suppresses its competitors M. si/varum was found being a hyperparasitoid physiologically, but the typical anterior position in larvae of both P. dubius, A. tedellae, C. cursi­ in the host seems to be necessary for successful tans, E. tibialis and A.? cingulipes. The adults suppression. Thus A. tedellae (and other com­ emerged during the period 15 June - 15 July petitors) inevitably dies if C. cursitans occupies

67 its anterior residence, but on nine occasions, 6. Agathis? cingulipes Nees where it was found in the abdomen of the host, A? cingulipes is a primary parasitoid attacking L1 both parasitoids were still alive in December or L2 of E. tedel/a during the first two weeks of though they were a little smaller than usual. July, and the species hibernates as L1 (Fig. lm) Functionally C. cursitans can be compared with in the host larva. The larvae are found at differ­ a hyperparasitoid as it is the primary enemy of ent places within the host, though mainly in the another parasitoid species, and only attacks abdomen. Super- and multiparasitism occur larvae of E. tedella that are bound to die. and A.? cingulipes probably uses its well de­ When C. cursitans itself is hyperparasitized by veloped mandibles in the competitive combat. M. silvarwn the effect on A. tedel/ae is either the The influence on the host physiology is much usual suppression or a situation where A. tedel­ less pronounced than that of the other primary lae is alive and normal while C. cursitans is small parasitoids. The reason might be that A.? cingu­ and weak. Neither superparasitism nor en­ lipes is primarily adapted to another host spe­ capsulation by haemocytes have been observed. cies, e. g. E. nanana. The effect on the host is difficult to observe as the presence of the young larva of A. tedel/ae 7. Trichogramma evanescens W estw. has already induced the changes, mentioned above, prior to its early death. Yet, these T. evanescens is a well known egg-parasitoid changes are less pronounced when C. cursitans found on several Lepidoptera-species, and its is present. (At 1 November the mean fresh­ development in eggs of E. tedella has been des­ cribed by Schedl (1951). weights of host larvae (L5) that were unpara­ sitized, and parasitized by P. dubius, A. tedellae The highest pecentage parasitism found during the long-term investigation in Denmark and (C. cursitans + A. tedel/ae) were 6.17, 5.90, 3.99 and 4.82 mg, respectively). was 32.8 (in 1973) while other years showed It is not known how closely C. cursitans is con­ percentages between 6.9 and 16.7. No signifi­ nected with E. tedella, but investigations of a cant response to host aggregations has been found; neither was there any demonstrable large number of larvae of P. clausthaliana and E. nanana did not yield this species. The connec­ correlation between the degree of parasitism tion with A. tedellae might be interpreted as a and the position of eggs on needles or branches. specific connection with E. tedella as well, but C. cursitans might well be associated with other 8. Dipriocampe sp. braconid species attacking other host species. The species was found as an ectoparasitoid on L3 and L4 of E. tedella; it was also found on P. clausthaliana in October. In October the larva 5. Exochus tibialis Hgn. pupates inside the mine of E. tedel/a, without E. tibialis attacks the first and second instars of making a cocoon. The adults emerge the fol­ E. tedel/a larvae and has been observed in host lowing spring and must then attack other host­ larvae from 10 July. The adults emerged from species. 23 June till 9 July with 4-5 days protandry. L1 Fiihrer (1970) has found Euderus albitarsis (Fig. 1f-g) was found in the haemolymph in the Zett. (Hymenoptera: Eulophidae) as an ecto­ abdomen of the host throughout the autumn parasitoid on E. tedella, but this species was and winter, and, without exception, together never found in the present investigation. Diprio­ with dead or dying larvae of P. dubius. Thus, E. campe sp. only occurred in certain years and tibialis must be considered a cleptoparasitoid at­ never exceeded 0.2 per cent parasitism. Con­ tracted to hosts that are parasitized by P. du­ sequently, it must be regarded as insignificant in bius. This may explain why Fiihrer (1964) found the dynamics of E. tedella. the species especially in young stands where P. dubius is also the dominant parasitoid. Superparasitism does occur and up to four Frequency and interrelations E. tibialis larvae have been found together with When data from all years and stands were used, one P. dubius larva in a single host. In the case of the means and rages of larval parasitism shown superparasitism only one larva survives, just as in Table 1 were found. E. tibialis always kills a P. dubius larva, probably In general, P. dubius was the dominant pri­ by means of its mandibles. mary parasitoid followed by A. tedellae,

68 Table I. Larval parasitism in E. tedella. A. tedellae always wins when competing with P. dubius. The results of multi-, clepto- and hyper­ parasitism, and the existence of more or less range "host" random superparasitism, are shown in Fig. 4. mean% of% (100%) The quantitatively most important multipara­ P. dubius 24.4 7.1-50.8 E. t. sitism (cleptoparasitism excluded) concerns P. A. tedellae 18.9 .8-53.7 E.t. dubius and A. tedel/ae. Apparently A. tedel/ae A.? cingulipes 1.6 .0-10.5 E. t. does not discriminate between healthy hosts and C. cursitans 5.3 .6-14.3 A. t. those parasitized by P. dubius; however, due to . E. tibialis .5 .0- .87 P. d. differences in the temporal and spatial distribu­ M. si/varum 9.0 2.5-22.1 P. d. tions of the two species, multiparasitism found M. si/varum 2.6 0.- 4.1 A. t. on branches in one particular height was only .412 times the value excepted if time and space considerations were disregarded. whereas A.? cingu/ipes was either absent or rare, except in one stand where 10.5 per cent Concluding remarks parasitism was found. Among the cleptopara­ In a broader population dynamic perspective, sitoids, C. cursitans was by far the most domi­ to be presented subsequently, the present para­ nant species, whereas E. tibialis was found only sitoid complex must be viewed as an entity with in some stands, and then in very low numbers. distinct spatial and temporal patterning, but Only one hyperparasitoid, M. silvarwn was subjected to modifications by interspecific in­ found attacking both P. dubius, A. tedel/ae and C. fluences. Still, a profound knowledge on the bi­ cursitans, though P. dubius was the preferred ology of the parasitoids is essential when realis­ host species. Fig. 3 shows a network diagram of tic host-parasitoid models are to be con­ the parasitoid-complex of E. tedel/a in North structed. The following relations should all be Zealand. clarified: The specific behaviour of the search­ The frequency and outcome of multipara­ ing females, handling time, sex-ratio, encapsula­ sitism have been studied for all species. Within tion in the host (immunity), super-, multi- and this parasitoid-complex the outcome of any spe­ hyperparasitism as well as other relations be­ cies composition within a host can be predicted tween the parasitoids concerned, temporal as the results have been found to follow a gen­ aspects, spatial distribution of the attacks, eral scheme. Thus, except for "rare incidents" searching effect, the influence of weather on ac-

p lTachinid

c H

Fig. 3. Diagram of the parasitoid complex of E. tedel/a. Average values on percentage parasitism, referring to the attacked species, are given. The broken arrow indicate that A. tedel/ae is an obligate winner in case of multipara­ sitism.

69 P. d. A. t. A. c. Tach E. t. C. c. M.s. P. d. s A.t. + s A.c. + s Tach E. t. + s C. c. + + + • M.s. H H H H H s

Fig. 4. The competitive relations between the parasitoids of E. tedel/a as these appear within the same host in- dividual. The arrows indicate the loosing species in case of multi- and cleptoparasitism, whereas (-) represents "not observed", (S) superparasitism occurs and (H) hyperparasitism occurs.

tivity and the influence of the conditions of the Acknowledgements locality (structure, micro-climate etc.) on I am greatful to Prof. E. Fiihrer, who kindly placed searching effect. his collection of parasitoids at my disposal, to 0. Lom­ In the previous section, observations are holdt for assistance with the identifications, and to presented that are necessary, but so far insuf­ Prof. C. Overgaard Nielsen, P. Holter and Dr. C. ficient, for the understanding of the forest­ Chapman-Andresen, who read and corrected the pest-parasitoid system and for correct inter­ draft of the manuscript. pretation of observed events in the dynamics of the populations. As the long-term investigation will later show, References the parasitoids of E. tedella are of real import­ Beddington, J. R., Free, C. A. & Lawton, J. H., 1978: ance as they cause mortalities ,that are high Characteristics of successful natural enemies in compared with the low fecundity of the host, models of biolo_gical control of insect pests. -Nature and as they have also a stabilizing effect on the 273:513-519. system. Through the present investigation it ap­ Capek, M., 1969: Zur Problematik der Insektenpara­ pears that, among the parasitoids, only P. du­ siten des Fichtennestwicklers Epinotia tedel/a (Cl.). - bius, A. tedel/ae, C. cursitans, M. si/varum and T. Acta Univ. Agri. Brno 38, rada C: 271-283. evanescens may have a significant effect on the Fiihrer, E., 1964: Zum Auftreten des Fichtennest­ dynamics of the host in Denmark, and that it wicklers Epiblema tedella Cl. (Lep., Tortricidae) in Schleswig-Holstein.- Z. ang. Ent. 54: 150-163. may be sufficient to concentrate on these five - ,1970: Studien iiber okologische Auswirkungen der species in the modelling of parasitism of E. te­ physiologischen Beeinflussung von Epiblema tedel/a della. Cl. durch entomophage Endoparasiten. - Habilit. In general, the importance of parasitoids as schr. Forst. Fak. Gottingen, 247 pp. decimating enemies may be underestimated, as - , 1972: Eine parasitiir bedingte Entwicklungsshem­ their presence apparently decreases host densi­ mung der Fliigelimaginalscheiben in der Larven ties in the field by a much greater factor than von Epiblema tedella Cl. (Lep., Tortricidae). Z. ang. that excepted from common assumptions (Bed­ Ent. 71: 113-120. dington, Free & Lawton, 1978). Further, para­ - , 1973: Der Einfluss zweier Endoparasiten auf die Gonadenentwicklung in der Larven von Epiblema sitoids may assist in keeping the host population (= Eucosma) tedel/a Cl. (Lep., Tortricidae). - Z. from escaping a domain of attraction at a low Parasitenk. 41: 187-206. density level, even though the observed parasi­ Rolling, C. S., 1959: Some characteristics of simple tism is not very high (Peterman, Clark & Hol­ types of predation and parasitism. - Can Ent. 91: ling, 1978). 385-98.

70 Jprgensen, 0. F., 1975: Competition among larvae of P. dubius klrekkes i perioden 10/6 til 15/7 med ea. Pimplopterus dubius Hgn. (Hymenoptera: Ichneu­ 9 dages protandri og <;?/0-forhold pa 1,67 i gennem­ monidae), a parasitoid of Epinotia tedella Cl. (Lepi­ snit. Den angriber I. Iarvestadium fra sidst i juni til doptera. Tortricidae).- Z. ang. Ent. 79: 301-309. sidst i juli. Herunder fprer den lreggebrodden ind Miinster-Swendsen, M., 1973a: Trrek afinsekt-parasi­ gennem abningen til den mine, som vrerten danner i toidernes biologi og vrertsrelationer. - Ent. Meddr grannaJene. Larver i miner, der er mere end 6-7 .41:3-15. mm lange, kan derfor ikke nas af P. dubius. Arten kan - , 1973b: En klrekkefrelde og faldgrubefrelde til in­ ikke skelne imellem parasiterede/uparasiterede vrer­ sekt-pkologiske underspgelser. - Flora og Fauna ter og fordelingen af afkom i vrerter fplger en tilfrel­ 79:85-92. dig fordeling (Fig. 2a). Den intraspecifikke konkur­ - & Nachman, G., 1978: Asynchrony in insect host­ rence imellem P. dubius-larver i samme vrert afgpres parasite interaction and its effect on stability, gennem fysiologisk undertrykkelse. studied by a simulation model.- J. Anim. Ecol. 47: A. tedellae klrekkes i perioden 15/6 til15/7 med ea. 9 159-171. dages protandri og <;?/0-forhold pa 1,06 i gennemsnit. Peterman, R. M., Clark, W. C. & Holling, C. S., 1978: Arten angriber I. eller 2. larvestadium fra 1/7 til The dynamics of resilience: Shifting stability do­ 1/8 og borer herunder Ireggebrodden direkte igen­ mains in fish and insect systems.- IRE report R-15, nem minens vreg, - en metode, der ikke fremkalder Vancouver: 1--47. synkroniseringsproblemer. A. tedellae skelner ikke Schedl, K. E., 1951: Der Fichtennestwickler (Epible­ imellem parasiterede/uparasiterede vrerter og super­ ma tedella Cl.) - Landesforstinsp. f. Kiirnten: 1-136. parasiteringen fplger pa udvalgte grenafsnit en tilfrel­ Thompson, W. R., 1957: A catalogue of the parasites dig fordeling (Fig. 2b ), mens angrebene i stprre skala and predators of insect pests. - Comm. Inst. of Bioi. er aggregerede. Den intraspecifikke konkurrence af. control, Ottawa. gpres rent fysisk, idet mandiblerne benyttes som vaben. M. si/varum klrekkes i perioden 15/6 til 15/7 med ea. 7 dages protandri. Den anbringer sine reg i parasi­ toid-larver, placerede i deres vrert, og angriber hyp­ Sammendrag pigst P. dubius. Superparasitering finder sted. C. cursitans klrekkes i perioden 20/6 til 25/7 med ea. Parasitoid komplekset hos Epinotia tedella 8 dages protandri. Arten er obligatorisk kleptopara­ (CL) (Lepidoptera: Tortricidae). sitoid, idet den udelukkende angriber E. tedella-lar­ Som et led i en stprre underspgelse af GrannaJevik­ ver, der allerede er parasiterede af A. tedellae. Lar­ lerens, Epinotia tedella (Cl.), populationsdynamik i ven findes forrest i vrertens hremocoel og drreber al­ Gribskov, Nordsjrelland, har parasitoiderne knyttet tid A. tedellae gennem fysiologisk undertrykkelse. Su­ til denne art vreret studeret indgaende igennem 9 ar. perparasitering er ikke observeret. Pimplopterus dubius (Hgn.) og Apanteles tedellae Nix. E. tibialis angriber tilsvarende kun vrerter, der al­ er helt dominerende blandt primrerparasitoiderne. lerede er parasiterede af P. dubius og drreber for­ De angribes selv af hver deres kleptoparasitoid, hen­ mentlig sidstnrevnte ved brug af mandiblerne. Super­ holdsvis Exochus tibialis Hgn. og Campoplex cursitans parasitering finder sted. (Hgn. ), mens alle fire arter angribes af en hyperpara­ Et diagram over parasitoid komplekset, med angi­ sitoid, Mesochorus si/varum Curt. De nrevnte arter er velser af gennemsnitlige parasiterings procenter er alle monovoltine og solitrere endoparasitoider. P. du­ vist pa Fig. 3. Nar A. tedellae og P. dubius tilfreldigvis bius og A. tedellae kan begge betragtes som vrertsspe­ er til stede i samme vrert, drrebes sidstnrevnte altid. cifikke i en beskrivelse af arternes dynamik inden for Et skema over multiparasitrere relationer som denne en Rpdgran-bevoksning. er vist i Fig. 4.

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