Field studies on the surface fauna of forests

by

J. van der Drift

Institute for Biological Field Rersearch (ITBON), Arnhem

Contents

I. Introduction 79 b. The lifecycle of problematicus

II. Technique 79 Herbst 87

III. Results 80 Fluctuations in 90 c. population density ....

a. Carabids 82 d. Local distribution 94

b. Other 85 e. Phenology 100

c. Spiders 85 V. Conclusion and Summary 102

IV. Discussion: VI. Literature 103

with other results 86 a. Comparison

I. INTRODUCTION

In most handbooks on forest entomology much stress desirable. This study is only concerned with the

laid the of second the is on importance predatory in question. It is hoped that a field study of the soil for habits be later. as enemies pupating noxious feeding can published

(ESCHERICH, 1923; GRAHAM, 1939). However, de- Little is known concerning the period of activity tailed investigations in the field on the significance of predators. LARSSON (1939) in and LIND- of these the who predators are scarce. ROTH in are only investigators,

In much work has been done the worked on carabids in this field. GILBERT on Recently

the life of four biology and feeding habits of Carabus species (KERN, (1956) published a study on history

1921; LENGERKEN, 1921; OERTEL, 1924; DELKES- species of Calathus. The results of LARSSON and

but LINDROTH based KAMP, 1930; KIRCHENER, 1927; JUNG, 1940) are mainly on capture frequencies adult material and the these observations and experiments were mainly done of specimens in museum on under conditions. of larvae. Often information from these laboratory FORBES (1880, 1882) occurrence

sometimes investigated the gut contents of many carabid species data was of necessity somewhat vague and and concluded that about of the food unreliable. 1/3—1/4 was even of origin. VITÉ (1953) studied the signifi- This study is intended to elucidate the activity cance of spiders in forests. periods of the surface fauna by means of a direct

If is of of method and to connect these with a predator importance as an enemy activity periods

coincide with the the life of the this noxious insects its activity must cycles species. For purpose a trap different activity of these insects. In the case of soil-surface technique was used. Traps were put in

these be the forest and continued predators predators must active at time areas trapping was during that noxious insects are present at the soil surface, several years.

around in search of Besides information the and life- e.g., caterpillars creeping pu- on activity period

which the of this the data pation sites. cycle, is main object paper,

For a better evaluation of the significance of the yielded information about fluctuations in population soil-surface local distribution and These predators more knowledge of the feed- density, phenology. ing habits and the period of activity in the field is results are reviewed in the "Discussion".

II. TECHNIQUE

The used this described A hole the bottom covered with trap technique in study was draining in was a in DER small-mesh , a previous paper (VAN DRIFT, 1951, p. 35). wire-netting. actively running

with surface of and the soil fell into the and col- Biscuit-tins a 24 cm square a on surface, trap were

of 25 sunk the the lected Some succeeded in depth cm, were to rim into ground. weekly. escaping during 80 J. VAN DER DRIFT

week the by flying out (very seldom) or by climbing undergrowth is replaced by a vegetation composed the sides of the evident that the of and out along tin. It is Vaccinium, grass mosses. This second plot

is method not equally efficient for the different (oak-mor) is situated at a distanceof about 150 metres

for the numbers from the first The oaks of the species. However, any one species one. are same age

but 13.5 trapped during a certain time are sufficiently com- they are only metres high with diameters

with to and to indicate 14.5 The the parable respect season place averaging cm. canopy covers 85% of

seasonal activity and local density. ground. The undergrowth consists of Vaccinium

The made oakwoods captures were in two adjacent Myrtillus L., Deschampsia flexuosa Trin. and Poly-

near Hoenderloo (Veluwe) and in a Scots pine wood trichum commune L., leaving only small patches of

at Schaarsbergen near Arnhem, both situated on dry litter. The soil is a true mor: an 8 cm thick layer of

and soils. the oakwoods 10 litter and humus the mineral poor sandy In two traps raw covers soil, which

of and each of is material. were put in two rows 5, rows traps in poor in organic

the rows being 10—20 metres apart. Trapping was The plot in the Scots pine wood occupies about done from March 1950 till November 1952. In the 5 ha (approx. 12 acres) and is surrounded by other

wood 20 4 of stands of Scots All the of the Scots pine traps were put in rows 5, pine. trees are same

rows and traps in each of the rows 50 metres apart. age (approx. 50 years), but in the northern part, the started March and stand of the Here trapping in 1951 was con- trees is rather close, the height varies tinued until November 1955. from 8—10 metres and the undergrowth consists

The first oakwood V2 ha. The of the Pleurozium schreberi (oak-mull) occupies mainly moss Mitten,

50 with which oaks are about years old, 15 metres high occupies about 70 % of the surface, the balance

diameters 18.5 The needle litter. The of litter and averaging cm (breast height). being pine layer moss,

about 90 % of the The under- humus 5—8 thick. the southern the canopy covers ground. is cm In part

consists of a of Holcus stand is the 5—7 growth patchy vegetation very open, trees are only metres

mollis Stellaria media and the consists L., Poa pratensis L., Cyrillo, high undergrowth of a patchy vege-

dioica Rubus tation of Calluna Hull, Urtica L., sp., Aegopodium podagraria heather, vulgaris especially

L., Glechoma hederacea L., Vinca minor L., and Am- on the Cladonia open spots, sp., Hypnum cupressi-

pelopsis quinquefolia R. et Sch. The litter occupies forme L. and several other mosses. Here the layer of

about of the and forms thin needles and humus about thick. The 30% area only a layer. moss, is 3 cm

The soil be characterised it has a difference between the two is caused may as a mull; areas partly by

rich in loose and crumbly structure and is humus. the soil texture since a layer of very coarse sand

favourable condition and the rich the and This herbaceous comes near surface in the southern part, be the result of the cultural the northern vegetation may regular depo- partly by circumstances since

sition of refuse from an adjacent garden. From this part, which previously carried oak coppice was subse-

plot the surface slopes slightly (2—3%) to the second quently tilled before the planting of the oak stand.

of the and soil conditions diminish November 1954 all the southern plot. Height trees In trees in part were

down the and the rich herbaceous felled and 1955 the regularly slope in June plot was ploughed.

III. RESULTS

the evident Since it is not practicable to present complete It is that the histograms of the populations

data for all here, in the in the different woods and from the different species they were deposited years

library of the Institute. Only one species, Ptero- agree closely. Some difference may be seen in the

in full. in stichus oblongopunctatus F., will be treated first occurrence of the young imagines the pine-

This medium sized carabid which abundant and oakwoods. Also the which be- is a was point at activity in all three the of The in weeks in the different areas during period study. gins spring may vary some discussed results are summarised in the histogram in Fig. 1. years. These phenomena will be in the

columns directed re- on however, of In the histogram the upwards section phenology. They are, minor

the number of males and those directed with the of present importance respect to general appearance downwards the number of females caught weekly. the histogram. The same applies to the other species.

The reproductive period extends from spring until Before considering the results it is important to

the fact that the and the decrease mid-summer, newly emerged imagines are present in stress increase in autumn. the number of the caused captures throughout year are FIELD STUDIES ON THE SURFACE FAUNA OF FORESTS 81

Fig. 1. Weekly captures of Pterostichus oblongopunctatus in two oakwoods

10 (each traps) and in a pine wood (20 traps).

in primarily by changes activity and secondarily by Fig. 2 demonstrates the different theoretical shapes

varied numbers of In most it is of the for two imagines. species histograms ranges of beginning activity clear that before the of emergence occurs long period (3 and 7 weeks) and four different periods of indi- catches. The highest small captures at the time of vidual activity (2, 3, 5 and 8 weeks). The population

and due low densities the the emergence afterwards, are to activity. are same (8 units in diagram), a

The be considered to indicate the distribution histograms may regular in the beginning of activity is The of the catches and weather activity. histogram weekly ex- assumed, mortality influences on activity of the total excluded. pressed as a percentage capture through- are The total number caught during the out the will be called an year activogram. activity period is proportionate to the length of the

Most and thus show individual the histograms, activograms too, activity, steepness of the curve is one or more curves. The the he determined the in shape of curves may by range beginning activity. attributed to two 3—5 the factors: Figures give average activograms of the other beetles and carabids, spiders. They are based 1. The varying time at which activity begins; the total catches in the different The on areas during the 2. length of the period of individual activity. 1950 1954 inclusive and years to they represent the When the of factor 1 is small and the indi- range weekly percentage of males and females of the total vidual short, a steep-sided, but short curve catch. The total activity numbers of males and females are will result. With a and a individual for each large range long given species. In general those species

a slow-sided and curve results etc. in lower activity long caught a number than 100 are omitted. 82 J. VAN DER DRIFT

2. Different of Fig. shapes histograms induced by different ranges of beginning activity

(3 and 7 weeks) and varying length of the individualperiod of activity, (2, 3, 5 and 8

weeks). The numbers of animals becoming active in the first, second, third etc. week

are represented by white and hatched columns alternatively.

A. CARABIDS

of With to the of From the activograms it appears that the activity reproductive activity. respect period

carabids is two be most restricted to a part of the year. Only reproduction types can distinguished.

Notiophilus biguttatus F. and N. rufipes Curt, and The first type is related to species that reproduce Their larvae perhaps also the other Notiophilus species occur in spring and/or early summer. occur

the in and takes in late throughout year. But within this period of activity summer emergence place summer there considerable difference and These be indi- is a in its intensity. In autumn. species may properly with larvae. nearly all species, maximum activity both of males cated as: spring-breeding species summer and females The this occurs during the oviposition period: following species belong to group: Cara- FIELD STUDIES ON THE SURFACE FAUNA OF FORESTS 83

nemoralis bus Müll., Pterostichus oblongopunctatus F., are present before emergence of the new generation.

P. have the and have angustatus Duft., P. strenuus Panz. In two species, They passed winter as imagines

C. nemoralis and P. the In oblongopunctatus, some mature probably reproduced preceding year. most

observed in the in is ovaries observed and ovi- eggs were ovaries autumn. It cases developing were

known whether these animals the old will the the not belonged to position likely occur at same time as few or to the new generation. This exceptional behaviour oviposition of the new generation. Only in a of of is reflected that time. a very small number the animals cases mature eggs were observed before also the of of C. nemoralis in In the with larvae it is difficult to by finding a pupa species summer animal of the spring and the exceptional occurrence of larvae of find out whether the reproducing is

P. both mentioned The of oblongopunctatus in winter, by new or of the previous generation. recapture LINDROTH (1945). individuals of Pterostichus oblongopunctatus marked

demon- The second type refers to species that reproduce during the preceding reproductive period,

late and Their larvae this in summer or summer autumn. strates the longevity of species. live in autumn, winter and spring and emergence Some species are not included in the above men- called: Villa shows distinct generally occurs in early summer. They are tioned types. Abax ater two

with winter larvae: of mature summer-breeding species Cara- periods emergence: eggs occur throughout bus Herbst, C. violaceus the of and larvae occur the problematicus purpurascens period activity throughout

in F., Cychrus rostratus L., Pterostichus madidus F., P. year. Evidently part of the population reproduces

Calathus and has larvae and the other niger Schall., micropterus Duft., C. erratus spring summer part

Sahib., C. fuscipes Goeze, C. melanocephalus L., reproduces in summer and has winter larvae.

anthobia Villa. In this is difficult the results of Amara group active imagines It more to interpret Notio-

forest carabids. ordinate five of total Fig. 3. Average activogram of the main Units on percents capture. 84 J. VAN DER DRIFT

Fig. 4. Average activograms of staphylinids and silphids. Fig. 5. Average activograms of dor-beetles and spiders. Units ordinate five of total ordinate five of total Units on percents capture. on percents capture.

philus species, N. palustris Duft, and N. aquaticus shows that related species have different periods of small the L., since they were caught in rather numbers. peak activity and that the successive peaks of and extend the whole Highest activity occurs in spring early summer. various species together throughout

observed in the ovaries Carabus nemoralis C. Mature eggs, however, were growing season, e.g. >-< v. pur-

almost the and was de- —C. and Pterostichus ob- throughout year emergence purascens>■ problematicus

monstrated in in It i-1P. P. madidus. In Calathus only one year early summer. longopunctatus niger.. -J

that obser- and this alternation does As seems likely emergence generally escapes Notiophilus not occur.

vation owing to the minor activity of newly emerged the feeding habits of these various Carabus species

animals. The of this alternation be of prolonged period reproduction prob- are probably very similar, may

be due small number of ably may to the mature eggs great ecological importance.

at time in female. The maximum the present any a num- The shape of the curves during reproductive

ber of relatively large eggs found in any female of period for the species with summer larvae is wholly whereas Abax and these species was 3, in Carabus, different from the shape of those with winter larvae.

the and medium sized Pterostichus this the first the rather but low large species In group curve is steep, between and and short which maximum was 20 30. long, indicating a period during

Of the Amara communis Panz. is first but individual species studied, activity at begins, a long activity.

discordant differ- In the only one that gave results in the the second type the curve is steep, high and short,

ent remarkable that this small but short individual years. It was in case highest indicating a range also, a

activity did not coincide with reproduction. activity.

of the of related It be observed that most the Comparison activograms species may in species num- FIELD STUDIES ON THE SURFACE FAUNA OF FORESTS 85

ber of females is much lower than the number of most in the first weeks of the reproductive period—-

males. the Calathus where Exceptions are species, especially in the spring-breeding species—whereas

especially in C. erratus the females outnumber the females are more numerous at the end of this period.

males far. this not by Of course proportion may re- These facts, may be attributed to the mate-searching

a since males and females of the males the first and the present true sex ratio, may activity in case to be different Males latter. active to a degree. predominate oviposition activity of the females in the

B. OTHER BEETLES

The in the of animals is low. staphylinids, caught traps, belonged to activity newly emerged very To

the larger species. Also in these species the greatest this group belong: Staphylinus compressus Marsh,

the olens Müll, and lateralis Grav. activity occurs during oviposition period. Newly Staphylinus Quedius

animals could in that this too the emerged only be distinguished one It seems in family species repro-

and larvae of three taken. So and have rather case only species were ducing in spring summer a long

time individual those the life cycle is mainly based on the of the period of activity, whereas repro-

and have short with oviposition period remains in some cases some- ducing in autumn a one activity

what doubtful. restricted An commencing during only a very period.

4 discerned: is Xantholinus linearis Fig. shows that three types can be exception with a very high and short The of curve in spring. periods peak activity

1. Species with summer larvae. Activity already alternate rather distinctly in the species Staphylinus

in remains low S. and With begins autumn but very until the be- brunnipes, chalcocephalus S. compressus.

of be observed the of Philonthus ginning spring. Eggs can in ova- exception decorus, males outnumber the

rioles but they are soft and white. At the beginning females in the captures again.

of the and both of The two carinata Herbst, and Phos- spring eggs are mature, activity, silphids, Silpha

males and Othius L. show similar have females, increases as in punctulatus phuga atrata activograms. They linearis larvae. Their rather Goeze and Xantholinus Ol. Philonthus de- summer reproductive period is

also be classed in this late with the carabids and corus Grav. may perhaps compared spring-breeding

At the end of soft After this rather group. August a specimen was staphylinids. period activity remains and of the observed. In winter this species is not active high. Emergence new generation produces

reproduction starts about a month later than in the some increase in the catches in September.

previous species. Quedius fuliginosus Grav. may also Geotrupes silvaticus Panz. and Ceratophyus ty-

this but data are than L. with life-habits which belong to group not more phaeus are species are different from the suggestive. quite preceding species. They are

not predators but feed on dung, toadstools etc. No

with larvae and numbers their 2. Species in summer autumn. large were caught during reproductive

Reproduction takes place in summer. It is not known period. The captures of Geotrupes silvaticus in-

whether the in in new generation emerges autumn or creased after the oviposition period. Since no newly

The first animals this spring. possibility is more probable since emerged are present, increment must

are after the be- be attributed increased surface mature eggs present immediately probably to activity

ginning of activity: Staphylinus chalcocephalus F. (increased searching for food). In the middle of

and F. the numbers taken but Staphylinus brunnipes August increase again, now

is many soft animals are present and this increment

with larvae. takes due of the 3. Species winter Reproduction to emergence new generation. In Cera-

place in late summer and autumn. Larvae are active tophyus typhaeus oviposition takes place from Novem-

throughout winter and disappear in early spring. ber till March. No soft animals were observed. It is

animals not observed but doubtful whether the in March has real Newly emerged were prob- peak any surface ably occur in early summer. Apparently the significance in view of the small numbers taken.

C. SPIDERS

The the real of the the the histograms of species given are activo- activity males. After mating period,

caused the of females grams. They are by very intense mating samples consist mainly bearing eggs (Lyco- 86 J. VAN DEB DRIFT

In Trochosa far the and short individual and sidae). terricola Thor, by most high, indicating a activity a

half small Males outnumber females far the numerous species, grown specimens are caught range. by in the This de- The three from spring until autumn. suggests a samples. lycosid species show separate of than of but first velopment to maturity more one year. periods peak activity, they cover only the the short In general the shape of curves is rather half of the growing-season.

IV. DISCUSSION

A. COMPARISON WITH OTHER RESULTS

in which hibernation takes LARSSON published 1939 a paper on types in place is of great ecological

Danish carabids with to their the larva-hibernators respect development. importance. However, among

This study is based on collections of larvae and some of the imagines also hibernate and so I prefer from Denmark. denote larvae and imagines mainly Two main types are to them as species with summer

and autumn- winter larvae this of distinguished: spring-breeding species respectively. Moreover way breeding species. In the first type several subtypes describing indicates at which time the most sus- are discerned with respect to the activity of the ceptible stage, the larva, occurs.

in autumn. to Both and fre- young generation According LARSSON LARSSON LINDQUIST give monthly nearly all adults die after reproduction and so the quencies of catches in Denmark and Sweden respect-

hibernate The assessed from spring-breeding species only as young ively. developmental type was the the adults these and the of imagines. In autumn-breeding species frequency curves occurrence larvae,

withstand the conditions but die adults etc. may severe winter immature

before the Their results with those of this in spring or summer young generation are compared study

stated in the several in Table numerals months emerges. As previous chapter 1. The Roman giving the individuals of the spring-breeding Pterostichus ob- with the highest frequencies, the month with the

which were marked and released italics. In there longopunctatus, highest being in general is a good

the the during reproductive period were recaptured agreement as to the type of each species. Only in next and thus the first does not hold, the of Carabus and Calathus year assumption case problematicus

least in the . There also the differences C. at are objections micropterus are appreciable. prob- the second lematicus to assumption. KERN (1912) showed by has summer larvae in Sweden and in

that Denmark and has larvae the Netherlands. histological investigation in Carabus species a winter in second is and this conclusion Calathus summer-breeder reproduction probable micropterus is a typical affirmed four found was by GILBERT (1956) in Calathus with winter larvae in this country. Larsson

The of small ovarioles in Carabus the in Denmark well, believes species. presence this to be case as but

after hibernation also this that Sweden problematicus just points to some reproduction occurs in spring. In possibility, but it is not certain that these animals spring-breeding with summer larvae is normal. The

in the the in moderateform is developed eggs preceding year. Though same tendency, though more seen field observations are not convincing in themselves, in Carabus violaceus, Calathus melanocephalus and in connection with the of KERN which findings it seems possibly in Cychrus rostratus in species a part that of the very likely some autumn-breeders, perhaps of the population in Sweden belongs to the summer

rather small the follow- larvae whereas a proportion, reproduce again type (= imago hibernator), in Den-

this is ing year. Probably also the case with Pteros- mark and the Netherlands only the other type occurs. tichus oblongopunctatus (spring-breeder), but the It is remarkable that the opposite situation, i.e.

of the females dissected. Sweden but ovaria hibernating were not species with winter larvae in summer

LINDROTH the larvae this does this material (1949) distinguished same two types in country, not occur in as LARSSON did, but denote them this of would be preferred to as though change reproductive type with shorter imago-hibernators and larva-hibernators since the more understandable in connection the

of the first Sweden Scandinavia. reproduction group in generally summers in occurred not before summer (June) and the stage in If we take the months with high frequencies, as FIELD STUDIES ON THE SURFACE FAUNA OF FORESTS 87

Sweden Denmark Netherlands (Lindroth '45) (Larsson '39)

Carabus nemoralis 111. V-VI /K-V, VIII III-IV-V

•Carabus problematicus Herbst. K-VI-VIII V, VII IX

Carabus violaceus L. VI-I7/-VIII VI-VII-VIII

"Carabus violaceus purpurascens F. VII-VIII

*Cychrus rostratus L. VI-VII-\III K//-VIII VIII-IX

Abax ater Villa. V-IX VI-IX

Pterostichus madidus F. VII-VIII

￿Pterostichus niger Schall. V-K/-VII-VIII VII- VIII VIII-IX

Pterostichus oblongopunctatus F. V-VI IV, (IX) 1V-V-VI

Pterostichus angustatus Duft. VI IV-V-VI

Pterostichus strenuus Panz M -VI IV IV-V-VI

*Ca!athus micropterus Duft. VI IV-X VIII-IX

*Calathus erratus Sahib. K/-VII-VII1 IV, VII-VIII VIII-IX

"Calathus fuscipes Goeze. VI- VII-VIII VII- VIII VIII-IX

Calathus piceus Marsh VIII-IX V, VIII-IX

"Calathus melanocephalus L. K/-VII VI-VII-VIII VIII-IX

highest TABLE I. Months of high capture frequencies of some forest carabids in Sweden and Denmark (months with fre- in in the Netherlands. with winterlarvae in the quencies Italics) compared with peak captures of the same species Species

Netherlands are indicated by an asterisk.

LINDROTH and larvae Scandinavia and given by LARSSON (Table 1), to corre- species, having summer in

spond with highest activity and reproductive period, winter larvae here, should be considered to have

it that in with winter appears most of the species reached the best adjustment to the Scandinavian

larvae the period of highest activity is earlier in climatological conditions by moving forward their Sweden than Denmark and Denmark earlier in in period of reproduction to such an extent that their

than the Netherlands: reach before The in Cychrus rostratus, Pteros- offspring can maturity winter. re-

tichus Calathus Calathus the larvae Carabus niger, erratus, fuscipes. verse is seen in summer species

This be winter possibly may connected with earlier nemoralis, Pterostichus oblongopunctatus, Pteros-

the northern earlier tichus and Pterostichus in countries resulting in an re- angustatus strenuus. Here

productive period. This gives the new generation an the period of reproduction is earlier in the southern reach which with the earlier opportunity to a stage in it can possibly countries, doubtlessly in connection better withstand the conditions. Should severewinter spring.

this interpretation be true, the above mentioned

B. THE LIFE CYCLE AND ACTIVITY FLUCTUATION OF CARABUS PROBLEMATICUS HERBST

The of Carabus 3 of activogram problematicus in Fig. by a period high captures indicating high activity shows the The that before period of high activity, starting during September. gonads are now mature;

at about the middle of there is and August, a long period copulations frequently occur eggs are deposited.

which rather small number First instar-larvae from October until (April—August) during a occur April,

of beetles is first catches slow caught weekly. The (April- indicating a very development during winter;

June) consist of hibernating imagines. They form the the 2nd instars occur from November (very small first inconspicuous peak in early June. From the numbers) until the middle of May, 3rd instars do not middle of the and before and the end of June new generation emerges appear April they disappear at This activity goes on until the first part of August. May. Evidently the duration of each instar is de- second termined produces the peak in July. Activity is only largely by temperature. Minimum time for due observed and the each of the 2nd to feeding, mating was not stage—with exception instar—seems middle of gonads were not yet mature. In the August to be about one month. there is distinct the followed stated above a minimum in catches, It was (p. 81) that the shape of the 88 J. VAN DEK DRIFT

of problematicus Herbst. Explana- Fig. 6. Histograms from capture data 1951 and hypothetical histogram Carabus tion in text. FIELD STUDIES ON THE SURFACE FAUNA OF FORESTS 89

is of the disturbance of the animals be histograms caused by the length period kept) may responsible

which first and the for this. The last had during activity begins by length emerged imagines an even the individual of activity. This was substantiated by shorter inactivity period and very possibly this also

observations and of this holds the field. When the animals on the occurrence activity true in are active

in species 1951. The hibernating imagines occurred again the reproductive organs are mature and copu-

from the middle of and small lations observed. and May were caught in are Dispersion in re-activation

numbers observations this individual only. From terrarium at in activity period gives rise again to a that time it appeared that their activity is slight, they rather steep and high curve. In all cases—also in under after about week other much than retire the ground cover one years—the captures are higher now

and that re-activated the latter of the of the individuals. they are in part in activity period immature

1 in August. ) This may be attributed the first place to a longer

animals with soft occurred individual the Newly emerged elytra activity period. Supposing range in

from mid June until the end of July and thus activity the re-activation to be four weeks, the animals will have of four commenced over a period of 5 weeks. Terrarium an individual activity period weeks, to

observations demonstrated animals the of the that these were cover period main capture (see hypo-

active for few weeks after thetical for the mature in very only a emergence: histogram activity period

males about two weeks, females about three weeks. Fig. 6). By this the takings of males and females in

After that period activity diminished greatly and the the second activity period should be about 2.0 and animals remained nearly motionless under ground 1.3 times higher respectively than in the first period.

for several fact the but cover weeks. A hypothetical histogram for In September curves are not only longer

this based these also much than the Almost period, on facts, is given in Fig. 6 higher July ones. twice

females taken = and the (lowest histogram, first curve), assuming a normal as many are (229 : 123 1.9)

distribution activated male about fivefold = of the occurrence of newly capture is (489 : 102 4.8).

animals in the successive weeks. This certainly must be attributed to higher activity

active in Animals becoming the first week and (intensity or duration per day) caused by mating.

for weeks be in in search for males remaining active two may caught Evidently mates, are more acti-

the first three weeks but the numbers caught in the vated than females.

second week the There less are twice as high as those caught in is a second, though important, reason

first and third week The holds catches the second (white columns). same why in activity period are higher

for animals becoming active in the second week, but than in the first. Whereas the September curve con-

their numbers animals sists of the however, are larger than the numbers of wholly young imagines, July one, becoming active in the first week according to the includes also hibernated imagines (black columns in

normal distribution (black columns). The numbers of the upper three histograms). These latter were active

animals the third week before columns but becoming active in are larger July (black upper histograms)

time again (white), but from hereon the numbers decrease. inactive at the the young imagines emerged. At

all numbers of animals the time re-activated. It Adding that may be caught reproductive they were was

with which rather not to the of these old gives a curve a peak corresponds possible estimate proportion

good with those of the field data (upper three histo- animals. The low numbers caught in June suggest

also that the small. grams, white columns) and a length, which proportion is

with the of the field It this that and corresponds length curves. is only in species immature mature

The earlier occurrence in the pinewood has to be activity curves are clearly separated, which is due to

ascribed and will be the fact that the individual to microclimatological influences resting period is so long

referred to in the last section. The field data show and that activity is so low during this period. In the

that other carabids first re-activation occurs about 7—8 weeks after summer breeding e.g. Carabus v. pur-

the first of the animals Pterostichus madidus appearance newly emerged purascens, Cychrus rostratus,

and the same distance is seen between and Pterostichus the into each peak captures niger, curves merge other. the first stated that the in the first and the second activity period. Assuming, In species it was

that the field much shorter and the animals on grounds given above, in young resting period was maintained imagines also have an activity period of 2—3 weeks, some activity. that have after this of it seems they a period in- activity lasting about 5 weeks. ') These terrarium observations were made indoors in a In terraria this was about 3 weeks but arti- period of about 1 Miss C. A. MEL- large square tray sq. meter by ficial circumstances and mutual (higher temperature CHIOR. 90 J. VAN DEH DRIFT

C. FLUCTUATIONS IN POPULATION DENSITY

motive It is of interest to inquire to what extent these known powers of these beetles, especially of samples reflect fluctuations in population density. It the larger carabids and Geotrupes silvaticus, of which

stated in that the marked taken was the previous sections changing specimens were within a week about numbers from week to week are mainly caused by hundred metres from the point of release, provide the

we the total of continuous from the changing activity. If, however, compare possibility immigration sur-

in the overall weather If captures successive years, roundings. notwithstanding this, trapping would conditions compensate to a fair degree and it is sup- have had a deleterious influence, the numbers of

that in total catches that showed decrease in posed arbitrary changes ex- species a succeeding years, 25% caused lower would have been than the number ceeding are by higher or density. larger that in-

second from the fact that creased remained It shown Table A difficulty arises re- or equal. is in 2 moval of the animals by sampling reduces population that this was only the case in 1953. In this table the

the density to an unknown degree. In first place it number of increasing, constant and decreasing species

be borne mind that the for the different the different must in traps are not at- are given years in tractive and thus the catching-capacity is proportional areas. In the oakwood 26 species are concerned, in

the surface the mutual of the which the to of tins. At a distance pinewood 19 species. Cases in years'

and surface of 25 the 10 less brackets. 50 metres a 25 x cm proportion captures were or are placed in It of the surface" to the be concluded from that does not "catching surrounding area is may this, trapping

1 ratio which that the result in an of the : 40.000, a strongly suggests ever decreasing density species

concerned. deduce from the traps have no deleterious effect on the surface fauna. It is not possible to

In the second place it must be pointed out that the available data to what extent this trapping technique

the surrounded forest influences the since data of plots carrying traps are by density comparable cap- from which areas of about the same composition. The well tures the animals were released again

Increase Constant Decrease

Oak mull

1950-51 10(+1) 8 4

1951-52 5 (+1) 11 8(+ l)

Oak mor

1950-51 11 ( + 1) 5 4 (+2)

1951-52 6 ( + 3) 6(+l) 9 (+1)

Pine (closed)

1951-52 7(+l) 4 ( + 1) 6

1952-53 3 (+2) 2 ( + 2) 10

1953-54 4 (+2) 5 ( + 3) 4 (+1)

1954-55 9 (+ 3) 2 3 (+2)

Pine (open)

1951-52 4 ( + 1) 5 8(+ l)

1952-53 2 5 (+1) 10 (+1)

1953-54 3 (+2) 4(4-2) 7 (+1)

1954-55 7 2 (+1) 5 (+4)

of TABLE 2. Frequency the number ofspecies showing increase, equal density or decrease in two suc-

cessive years. FIELD STUDIES ON THE SURFACE FAUNA OF FORESTS 91

and the other hand not animals to the first week of The ratio are lacking on trapping was caught up July. false performed in enclosed areas. of the total annual captures in this case gives a

Table ratio the catches from the the In 3 the for one year impression of change in population (1.35 in

to the next is for the different Values closed and 1.46 in the Based on the given areas. open part).

in brackets. ratio be based on captures of 10 or less are placed mature imagines this more correctly may With of the the evaluated and Carabus exception 1955/54 ratio extremes as 0.48 0.36 respectively. In

are 0.02 and 17.05 but 87 % lies between 0.2 and problematicus, normally somewhat later than the

4.00, 26% lies between 0.75 and 1.25, the arbitrary other species, only in oak-mull freshly emerged ani-

limits for 34% of the values mals the first week of After that unchanged density; ex- were caught in July.

is in in ceed 1.25 against 40% which are below 0.75. It date this area, as the others, freshly emerged evident that there animals taken and from this too is no significant were only occasionally mature ani-

below which should indicate mals small numbers with excess of ratios 1, a were caught in compared

decrease removal of the animals. It the steady by may preceding year. evident from the that the be seen that both in the two oak plots and in the It is foregoing sharp two pineplots the changes in each pair of plots are decrease in density from 1951-52 is not likely to be generally in the same direction. To 63 cases with attributed to the high catches and thus to the removal

there with of number of animals 1951. If this had corresponding development were 11 cases a large in opposite tendency (ratio's 1955/54 and values in been the cause, the numbers of larvae would have brackets not considered). been influenced and this apparently has not been the

in For the the decrease in The highest increases took place the year 1951 case. same reason density especially in the carabid species with winter larvae. can also not be ascribed to unfavourable conditions for larval The sudden de- It is not possible to trace the causes of this increase. development in winter.

there the forest in both all deleterious Though was no trapping in pine in crease species in areas suggests

the numbers 1951 influences in the first of 1950, large captured in suggest a meteorological part July.

there well and if this is it is these the rainfalls combined high increase as true Possibly were very heavy

that climatic influences involved. The with The first have been probable are high temperatures. may animals winter of 1950-1951 was characterised by a normal detrimental for the freshly emerged activated

short frost followed the autumn, a period in December, greatly by exceptional high temperatures.

mild and normal Before and It evident that the differ by a winter a spring. is population changes

Nevertheless there after the frost period precipitation was above aver- widely in the different species. is

It be assumed that these conditions closer within the two age. may were a conformity developmental larvae favourable for the development of winter larvae. types. Thus the species with winter show a Indeed Carabus from numerous larvae of problematicus significant increase 1950 to 1951 (av. ratio 6.90) and Carabus taken, these whereas the with larvae remain at v. purpurascens were being species summer effi- the only species in which the larvae are rather about the same level during that period (av. ratio

used. decrease ciently caught by the trapping technique 0.97). The following year produced a sharp

After the year of high density another mild winter in the first group (av. ratio 0.36) but now the species

shorter and less followed with only a severe frost with summer larvae show some increase (av. ratio

than the The of The form period in preceding year. captures 1.38). Notiophilus species a homogeneous inrvae than in the winter of with ratios of 1.18 and 2.10 were significantly larger group on themselves,

in oakwood and in the This 1950-51, the 88 26 resp. Following respectively two years. conformity in the the number of within of the de- high population density in 1951, population changes groups same hibernating imagines in 1952 was relatively large and velopmental type suggests also a directing influence in the earlier factors species, C. v. purpurascens, large num- of meteorological on population density. bers of taken. After the first The 1955 shows distinct increase in several young imagines were year a week catches decreased the closed of the and of July the of this species species in part pinewood, a

the oak forest mature im- decrease in the This difference is caused abruptly. In only some open part. agines were taken, in the pine forest these numbers by the fact that in the winter of 1954-55 the trees in

still but small in with the felled. this were large yet comparison the open part were Although may have

numbers of adults this influenced the to very large freshly emerged in adjacent parts some degree, it seems

in area. probable that, without any alteration the stand,

The total this the would have been the high capture for 1952 in area is population changes in same caused the number of direction as in the unaltered by very large freshly emerged they were part. 92 J. VAN DER DRIFT

1951 1951 1952 1953 1954 1955

1950 1951 1952 1953 1954

Notiophilus c 7 3.00 (.43) (1.00) (.33)

aquaticus d 16 .50 (.88) (.29) (7.50)

81 1.29 .46 Staphylinus a chalcocephalus b 578 1.56 .30

.35 .04 (2.00) c 78 (5.00)

d 11 .36 .00

Staphylinus a 26 1.04 1.04 brunnipes b 35 1.94 1.06

.09 Staphylinus a 9 (.11)

b 3 .19 compressus (.33)

Quedius a 19 .79 .79 fuliginosus b 2 (.29) (1.50)

13 .26 .87 Quedius a

lateralis b 45 .85 .85

3.03 Philonthus a 219 1.01

decorus b 3 (.43) (4.00)

1.56 1.00 Othius a 70

punctulatus b 84 1.06 1.38 .89 1.64 .29 .07 c 46

d 26 .54 1.62 .21 (.22)

Silpha a 21 4.20 1.33

carinata b 79 2.26 .58

.55 1.00 1.24 c 18 1.72

d 4 (4.00) .50 1.00 (.25)

1.83 .82 Phosphuga a 44

atrata b 46 1.05 .65

.77 .64 Geotrupes a 44 silvaticus b 1417 2.24 .91

.78 .15 1.35 3.87 c 300

d 42 1.29 .24 .92 1.00

1.24 Trochosa a 137 .50

terricola b 200 .61 1.31

.78 .65 .53 2.55 c 919 1.83 d 493 .72 .85 .65

1.25 Lycosa a 20 .31 1.47 chelata b 135 .69

3.08 1.49 .02 (26.00) c 12 2.53 .05 d 40 .75 (15.00)

9 .77 Tarentula a (4.50)

trabalis b 18 .82 1.11

in different TABLE 3. Ratio’s of successive year captures plots, a = oak mull

b = oak mor c = pine (closed part) d = pine (open part)

total of 1951 is in the first column. The capture given FIELD STUDIES ON THE SURFACE FAUNA OF FORESTS 93

1951 1951 1952 1953 1954 1955

1952 1953 1954 1950 1951

.29 Carabus a 371 1.98

problematicus b 314 1.77 .17 1.54 1.24 c 126 .40 .80

d 142 .41 .64 1.84 .47

.18 Carabus v. a 194 11.41

297 12.38 .16 purpurascens b .48 .07 1.88 7.69 c 192 (1.35) .53 d 114 (1.46) .36 .20 .85

Carabus a 49 1.22 1.16

nemoralis b 15 1.25 .47

3.00 .53 Cychrus a 36

rostratus b 9 (1.50) (.89)

.60 Abax a 1278 2.20

ater b 896 1.70 .38

.92 .28 Pterostichus a 46 .20 madidus b 704 3.81

.20 Pterostichus a 358 17.05

niger b 239 8.85 .17

432 .78 1.90 Pterostichus a

oblongopunctatus b 198 .61 .92

c 287 1.56 .63 .82

d 463 .66 .96 1.14

2.50 1.38 .89 1.59 Pterostichus c 16

26 1.04 1.22 1.00 3.70 angustatus d

Pterostichus a 32 .78

strenuus b 5 (1.80)

.63 .85 2.56 .36 Calathus c 43 5.06 .22 micropterus d 110 .37 .80

Calathus c 15 .27 (1.25) (.80) (8.00)

erratus d 61 .46 .72 .25 (12.00)

29 .28 (.56) (2.40) Calathus c (1.13)

fuscipes d 35 .74 1.08 .61 .24

Calathus c 4 (1.25) (1.80) (.78) (.00)

melanocephalus d 31 .68 .48 (1.20) (.08)

Calathus a 63 3.71 .87

piceus b 16 (8.00) .75

2.46 Notiophilus a 48 biguttatus b 31 1.90 3.45 .28 .14 2.94 c 114 d 112 1.06 .34 .22 4.45

2.96 Notiophilus a 74

rufipes b 78 2.32 1.78 .30 .78 1.16 c 93 2.20 d 60 .88 .42 .45

Notiophilus a 2 (2.00) palustris b 26 1.46

c 9 (3.89) .17 (.83) (1.00)

d 6 (1.50) (.11) (4.00) (3.25) 94 J. VAN DER DRIFT

D. LOCAL DISTRIBUTION

these 1. Comparison of the occurrence in oak-mull and most species in two plots differed in each of

the three of the oak-mor years investigation as may be seen

from the total yearly captures.

said the the It is that and thus As was in description, experimental plots true groundcover, vegetation

the oak-mull and oak-mor close microclimate different but it has been assumed carrying are very to are and the be- that this difference of each other (about 150 m apart) area in is negligible importance with

forms rather from and so to tween a regular transition one to respect to activity captures. For com- the other. It is not surprising that the two plots have parison, the total annual capture is regarded as the the densities of best available index of These all species in common. However, density. are given in

7. Fig. Comparison of captures of common species in oak mull and oak mor. FIELD STUDIES ON THE SURFACE FAUNA OF FORESTS 95

Fig. 7 for each plot in 1950, 1951 and 1952. The the difference in the two stands. This results in the

distant from the 45°-line the more a species is greater following comparitive statement:

oak-mull Both stands oak-mor More numerous in about equal More numerous in

1 Carabus nemoralis 10" Carabus problematicus 17 Pterostichus madidus

e 2 rostratus II Carabus violaceus 18° Cychrus purpuras- Notiophilus palustris

3 Abax ater cens 19° Staphylinus chalcocephalus

4" Pterostichus oblongopunctatus 12 Pterostichus niger 20 Quedius lateralis

5 Calathus piceus IS" Notiophilus rufipes 21° Othius punctulatus

6" Notiophilus biguttatus 14 Phosphuga atrata 22° Silpha carinata

7 silvaticus Staphylinus compressus 15 Staphylinus brunnipes 23° Geotrupes

8 Quedius fuliginosus 16° Trochosa terricola 24° Lycosa chelata

9 Philonthus decorus 25 Tarentula trabalis 96 J. VAN' DER DRIFT

the of the densities. has Since there is no difference in accessibility at various A description of the wood two plots the difference in density must be caused already been given in the second section. Fig. 8 by habitat factors, of which the physical properties gives diagrams of the most important vegetation of soil and litter layer and the composition of the characteristics and additional data. In addition to

the It that these factors biotic undergrowth are most apparent. seems an important factor, influencing the species of the first column are favoured by a the distribution, is operative. On the places indicated litter and loose and crumbly soil with a thin layer in the diagram ant-hills are present. Ants ( Formica

of the third column dense of affect the those by a vegetation rufa polyctena Förster) sampling results,

Vaccinium and a thick raw humus layer. since they were frequently observed attacking the

The of the second smaller individuals and them of the species group are apparently dragging out these factors. worth that the visited unaffected by It is noting traps. Only neighbouring traps were several Notio- indicated the The small congeneric species (of Pterostichus, regularly as in diagram. and philus, Staphylinus Quedius) are distributed over catches from these tins, however, were not only different With to the factors caused in the The of groups. respect involved, by ant activity tins. use a

Pterostichus niger, Notiophilus rufipes and Staphy- modified technique in which the animals, entering linus brunnipes should have a wider ecological ampli- the trap fell down into tubes of alcohol at the bottom, tude than the other of the well direct observations the field two species same genus. as as in suggests

Furthermore it be stressed that the number of that soil scoured ants is may intensively by only sparsely three also carabid species in each of these groups, which occur occupied by most of the smaller species. In in with winter the forest the pinewood (marked an asterisk) is greatest the 1954-55 the open part of was

the out of and cut down. be in the dia- in "mor-preferring" group (6 spp. 9) As may seen vegetation

in smallest the "mull-preferring" one (2 spp. out of 9), grams this corresponds to the two southern rows of the third intermediate this The soil surface remained unaffected group being in respect traps. actually

out of the total of This that the until but it then The ant colonies (4 spp. 7). suggests June was ploughed.

humus both the and had moved before this the SW of raw layer (present in pinewood happened: one out

with habitat in oak-mor) is of importance respect to the experimental plot, the E one about 50 m in a the forest border. preference. northerly direction, near new

The results of only four species are presented in the 2. Distribution pattern in the pine wood detail. In Fig. 9 the figures indicate percentages

The of in the total different continuous trapping over a period 5 years of years' catch given by the traps. the allows of the distribution The total catch the base of the pinewood a comparison is given at diagram.

in In in pattern of the different species different years and Carabus v. purpurascens, the distribution the

Fig. 8. Characteristics of the pine wood area.

A. Arrangement and numbering of the traps in the experimental plot. B. Height of trees in metres.

C. D. of needle litter. E. Percentages coverage of canopy. Percentages coverage Percentages

of heather = F. of Pleurozium Schre- coverage + very scarcely occuring. Percentages coverage and of cleared beri. G. Ant hills of Formica rufa polyctena area activity. H. Area in Novem-

ber 1954. FIELD STUDIES ON THE SURFACE FAUNA OF FORESTS 97

Distribution of four carabid and in wood five Fig. 9. pattern species one Geotrupes pine in

successive years. Figures give percentages of total year capture in each of the traps indicated

at the bottom of each diagram.

1951 is about the there is than in the years and 1952 same; some corresponding traps of the preceding the preference for the closed part of the forest but the years. From remaining part of the forest, how-

in species occurs frequently also in the open part. In ever, captures were significantly higher than the the 1953 and 1954 the far the loss in the felled years captures were very preceding year, exceeding by small, influencing the significance of the percentage part, suggesting a remarkable increase in population values. remarkable that and rela- the catches It is in traps 4 5 density. Surprisingly large are in traps 1

numbers taken. In 1955 the and 2 the of The tively large were cap- throughout period activity. larvae,

in smaller still taken in much smaller tures the felled area were very small, though numbers (numbers 98 J. VAN DER DRIFT

in winter in taken 1951/52 indicated diagram under It may be seen that in the last three species the

1951 etc.) show a distributionthat rather distribution in the successive is corresponds pattern years rather

well with the distribution of the It be stable. There is no indication of distinct imagines. may a change in

concluded that the distributionpattern remained con- distribution with changing density.

in the first Then, after a stant two years. significant It must be admitted that the method is rather

the increased and reduction in numbers, density again (in coarse it is possible that more refined sampling

the unchanged part of the forest), resulting in a pat- methods would indicate such differences in distri-

different from the of the first bution at different densities. It how- tern quite pattern two seems probable,

that these differences years. ever, are only slight.

Pterostichus shows distribution The do indi- oblongopunctatus a remaining species again not give

different from the distribution of the cations of distinct the The dia- quite previous changes over years. Numbers and the distri- species. change only slightly grams given in Fig. 10 present the distribution

bution the based the total catches pattern remains virtually same throughout pattern, on of 1951—1954.

evident is is the four years. It seems that this species The total number caught indicated at the bottom.

the with dense Pleurozium fall four scarce at highest parts a They apparently into groups; species with-

cover. On the other hand, it avoids areas traversed out distinct difference in for or any preference one

Formica is indicated the other of these varied Carabus intensively by rufa as by areas: problematicus;

small from 4, and which are with less very capture traps 5 14, species a more or pronounced preference for

all situated where ant is the and closed of the forest with its activity very great. Probably higher part

in the small catches trap 6 were due to the extremely accompanying properties: Carabus v. purpurascens,

and situation of this the northern dry sunny trap: Notiophilus biguttatus and N. rufipes, Geotrupes sil-

of small heather this Othius margin a patch. Evidently vaticus, Staphylinus chalcocephalus, punctu- the species prefers light and open forest vegetation. latus, Silpha carinata and Trochosa terricola; species After the with clear-cutting number taken decreased to a preference for the lower and open part of the but after few forest with some extent, even ploughing a were its characteristics: Pterostichus oblongo-

still taken. In 1 and 16 remarkable increase P. Calathus traps a punctatus, angustatus, micropterus, Ly- in capture suggesting a re-distribution, the cause of cosa chelata; species showing a marked peak in the which in unknown. part of the low forest with heather undergrowth:

The distribution of Calathus micropterus also shows Calathus erratus, C. melanocephalus and C. fuscipes. little very change over the years 1951 to 1954. It is It is remarkable here that the congeneric species show somewhat different small about in 1953 probably due to the the same distribution pattern: Pterostichus, catches, but the general type of distribution remains Calathus and Notiophilus. unaffected. The distribution the followed has had average over years Clearing by ploughing a great 1951—1954 rather well influence the distribution agrees with the distribution on of the species. Before of the be less the effect of the preceding species. However, it seems to ploughing clearing was slight only affected by ant activity, since captures in traps 5 in Pterostichus oblongopunctatus and Trochosa terri- and 14 rather Clear seems to have cola and in the latter small are high. cutting apparently species a affected the distribution only slightly, though the P.population maintained itself after ploughing. Of numbers are reduced. Even after few individuals markedly plough- oblongopunctatus only a were trapped

this ing species is caught regularly on the bare sand after ploughing in this plot from which this species has been eradicated. plain. probably now

silvaticus concentrated the Other that almost Geoptrupes is greatly in species disappeared wholly are

of the forest with dominant Pleurozium Carabus Calathus and highest part a v. purpurascens, fuscipes, vegetation on the floor and thus seems to have a Silpha carinata whereas Carabus problematicus de-

different from the shown creased the other hand preference quite preference considerably. On some species

Pterostichus Carabus increased the cleared after by oblongopunctatus. As in v. on plot even ploughing:

in purpurascens captures traps 9 and 10 are con- Pterostichus angustatus, Notiophilus biguttatus and lower than the stantly in adjacent traps. It is re- N. rufipes. In the first species it is most probably a markable that the distribution pattern of this species direct influence of the clearing. Compared with the is since it so distinct, is known to run rather quickly average captures of this species in the preceding four and It that the for which frequently. suggests preference years, differed only slightly from each other, the is but the the most northern of higher part very pronounced, operative row traps yielded about the factors are unknown. same number, the second row in the new forest FIELD STUDIES ON THE SURFACE FAUNA OF FORESTS 99

Fig. 10. Distribution pattern of surface arthropods in pine wood, based on captures from

of 1951 until 1954 inclusive. Numbers give percentage total capture, indicated behind the

of the name species.

in border yielded twice as many and the two rows Several species, up till now never found in the

much four times occurred the sand the clearing as as as many. Evidently pinewood, suddenly on plain. this species prefers the cleared surface, the numbers Among them must be mentioned Broscus cephalotes diminished, however, after ploughing. The first fact (21 ind.), occurring immediately after felling and

observations mentioned LINDROTH the agrees with the by present throughout following year. Apparently

(1945) that P. angustatus suddenly increases on burnt this species was attracted by the new conditions. areas in the forest. 100 J. VAN DER DRIFT

E. PHENOLOGY

and Trochosa terricola indicated. that Though the series of years is short it is of interest to are It seems

the of of Pterostichus trace the validity of the data with respect to pheno- period occurrence oblongo-

be described is rather well correlated with logical phenomena. Phenology may as punctatus surpassing

maximum "the study of the sequence of natural events through- the 10°C level of the average decade

the and the in date from out year, changes year to temperature.

and from The In Carabus is correlated year place to place" (WILLIAMS, 1949). v. purpurascens activity

of the of surface with the decade minimum quantitative description occurrence surpassing average temper-

in thus also ature of 9°C. Carabus and Trochosa fauna-species as was given chapter 3 may In problematicus be reckoned the second terricola the and of as phenological. Here only beginning ending activity are at

in different levels: in part of the definition matters: the changes date C. problematicus these are average

decade minima and in from year to year and from place to place. of 8° 6°C respectively and

There several drawbacks the available Trochosa terricola 1° and 6°C That the are in ma- respectively.

correlation terial with respect to phenology. The first concerns is better with maximum temperatures in the rather total from Pterostichus and with the conspicuous changes in capture minimum temperatures in

to and from to due to different other be caused the fact that the first year year place place, species may by densities. In a year or on a place with higher density species has mainly diurnal activity, the others noc-

be earlier date. Thus turnal first capture may expected at an activity. It is evident that the correlations it must be kept in mind that late occurrence of a stated do not have the character of a causal relation-

in the catches caused its low species may be by ship. Nevertheless they indicate that temperature

This be avoided in density. difficulty can to some ex- may be an important factor activating the species incidental late catches concerned. This that tent by neglecting early or in is sustained by the fact extreme

A is years with high density. second difficulty the high and extreme low temperatures increase and de- interval of week between dates a two collecting by crease the catches. which correlate the catch animals it is impossible to exactly Since react to microclimatological con-

conditions. with meteorological Since no meteoro- ditions, it is clear that there must be phenological

data available for the logical are region concerned, differences in so markedly diverging stands as the the weeks of the first and the last and the oakwoods. uninterrupted oc- pinewood For comparison it is

with the of that both woods the currence are compared decade-averages necessary in species are caught the maximum and minimum temperatures of the in rather large numbers. This is the case with

of Bilt about 50 Pterostichus in Royal Meteorological Institute De oblongopunctatus both years that cap- km of these data with those of made the and the west. Comparison tures were simultaneously in pine- km Winterswijk (about 60 east) shows a rather good oakwood. The first catches were a week earlier in

and thus it taken that agreement may be for granted the pinewood and a peak was reached sooner. A the of these data characteristics of the of application as great difference was noted in the first occurrence macroclimate is valid. the freshly emerged adults in this species. In the

in all the and in suffi- Only species caught years pinewood this date was three weeks earlier in both cient numbers handled in this viz. the were way years. carabids Pterostichus oblongopunctatus, Carahus v. The first fact points to earlier activation of the ani-

Tro- in purpurascens, C. problematicus and the spider mals spring, the second one to quicker development

chosa terricola. In is in Fig. 11 a graph given of the of larvae summer, both probably caused by higher

decade and the litter of the average maximum minimum temperatures temperatures in layer pinewood. of the years 1950—1955. This earlier first occurrence in the pinewood by 1—2

The Pterostichus Carabus and periods of activity of oblongo- weeks, was noted also for problematicus

Carabus punctatus, problematicus, C. purpurascens C. v. purpurascens. Fig. 11. Period of occurrence of Pterostichus Carabus Carabus regular oblongopunctatus, v. purpurascens, pro- blematicus and Trichosa in relation maximum and minimum terricola to average decade average decade tempera-

of the broken line. tures respectively. The fifty years average these temperatures is given by 102 J. VAN DER DRIFT

V. CONCLUSION AND SUMMARY

Baitless trapping of the macroarthropod surface fauna ent degree in the different species; mature imagines,

in an oak- and a Scots pinewood for several successive the re-activated old and young animals which re-

has revealed that each has character- years species its produce.

of often marked The and Carabus istic period occurrence, showing a long intense resting period in related and difference from that of species (Fig. 3, 4 problematicus causes two peaks in the histogram

differ and 5). The periods of occurrence only slightly representing immature mature activity (Fig. 3,

and from to In the other the is shorter from year to year place place (Fig. 1), 6). species resting period

they coincide with differences in temperature (Fig. and inactivation less intense and therefore the two

caused these into each other 11) and they are probably mainly by activity periods merge (Fig. 3). differences. Within the of distinct the fluctuations of period occurrence In general in density species in

periodic differences in the catches can be recognised, the different plots agree with each other rather well

caused differences The mainly by periodic in activity. (Table 3). It is suggested that the fluctuations are histogram of the weekly captures in percentages of mainly caused by meteorological conditions. In the

is the total year capture called activogram. The population changes which occurred during these five activogram characterises the species with respect to years, there is a greater resemblance between species with which have the of life either its developmental type: species summer larvae, same type cycle (i.e. with and larvae than between reproduction highest captures in spring winter or summer larvae) species

winter larvae, and/or early summer, and species with of different type. This also points to the fact that the with The of conditions considerable. these items in summer and/or autumn. influence meteorological is shape of the curves characterises the species with The influence of continued bait-less trapping upon respect to the dispersion in the time at which activity local population density could not be accurately as- first begins and the individual duration of activity: sessed but this is believed to be negligible. The ratios small and short individual of the annual in two for dispersion activity giving captures any successive years rise and short and the reverse all do show of decrease to a steep-sided curve species not a tendency slow-sided and to a long curve (Fig. 2). Comparison (Table 2). of the data here with those from literature The distribution little the presented pattern changes during

(Table 1) shows that in the category of "species with successive years, notwithstanding fluctuations in den- winter larvae", is the reproductive period occurs pro- sity, (Fig. 9). It clear that the preferences of

earlier with latitude. several for certain conditions gressively increasing In two species are very pro-

Carabus and Calathus within which species, problematicus micro- nounced, even areas superficially appear pterus, this results in a complete change-over in the homogeneous. The analysis of the causative factors

life the type of cycle from one with winter larvae in will be a subject for further research. south the with larvae much further to type summer north. It that this is suggested is an adjustment to Acknowledgements the adverse winter conditions in northern latitudes.

the of with for the thank the In category "species summer larvae", a It is a pleasant duty author to retardation of the of the forests in which collected reproductive period occurs, prob- owners was during ably caused by the later spring. so long a time: the Board and the director of the In the of life National Park "De type cycle involving winter larvae, Hoge Veluwe", ir. J. H. VAN TUYL, three different of be dis- and Douarière types active imagines can S. A. M. REPELAER VAN SPIJKENISSE,

that of "Deelerwoud". I also indebted cerned, viz.: beetles, hibernated as imagines, owner am to the reproduced in preceding year and which are ex- Dr. P. F. BARON VAN HEERDT (Utrecht) for his as-

for second of the material and pected to reproduce a time; newly emerged sistance in collecting part to

after short of Dr. EDWARD BROADHEAD for of the adults, which, a period intense activity, (Leeds) correction have in which reduced differ- a period activity is to a english text.

Tevens mededeling ITBON nr. 41, 1959. FIELD STUDIES ON THE SURFACE FAUNA OF FOHESTS 103

VI. LITERATURE

DELKESKAMP, K., 1930: Biologische Studien über Carabus KEHN, P., 1912: Über die Fortpflanzung und Eibablage

nemoralis Müll. Z. Morph, ökol. Tiere 19, (1), 1. bei einigen Caraben. Zool. Anz. 40, 345-351.

EMDEN, F. VAN, 1933: Über die erbliche Bindung von KERN, P., 1921: Beitrage zur Biologie der Caraben. Entom. _., D = BI. Latenzen an Jahreszeiten. V Congres Intern. d'Entom. 17.

II Travaux. KIRCHENER, H., 1927: Biologische Studien über Carabus

ESCHERICH, K., 1923: Die Forstinsekten Mitteleuropas II cancellatus. Z. Morph. Ökol. Tiere, 7, 489-534.

Parey, Berlin. LARSSON, S. W., 1939: Entwicklungstypen und Entwick-

FORBES, S. A., 1882: The food relations of the Carabidae lungszeiten der dänischen Carabiden. Entoni. Medd. 20,

and Coccinellidae. Bull. 111. State Lab. of Nat. Hist. 1, 277-554.

(6), 33-60. LENGERKEN, H. V., 1921: Carabus auratus und seine Larve.

GILBERT, O., 1956: The Natural Histories of four species Arch. Naturgesch. Abt. A. 87.

of in C. 1949: Die Calathus, living on sand dunes Anglesey, North LINDROTH, H., Fennoskandischen Carabiden

Wales. Oikos 7, 1, 22-47. Medd. Göteborgs Mus. Zool. Avdeln. 122.

GRAHAM, S. A., 1939: Principles of forest Entomology. OERTEL, R., 1924: Biologische Studien über Carabus gra-

McGraw Hill, New York. nulatus Zool. Jb. Syst. 48, 299.

41: Carabus violaceus L. und 1953: über die HENSELEB, C., 1940, pur- VITE, J. P., Untersuchungen ökologische

Entom. 152- im Z. purascens F. in Deutschland. Bl. 36, (5), und forstliche Bedeutung der Spinnen Walde.

157, and id. •37, (3), 117-118. Angew. Entom. 34, (3), 313-334.

Carabus WILLIAMS, C. 1949: The of the seasons. New JUNG, W., 1940: Ernährungsversuche an Arten. B., Biology Entom. Bl. 36. Naturalist 5.