Colour variation in two coastal popuiations of the wartbiter

(Decticus verrucivorus (L.); Insecta: ) in relation

to biotope

Rolf Tienstra

P.G. Otterweg 5

8459 EV Luinjeberd

Photographs: T. Tienstra - van derStaak, exceptfor nrs. 1,3 and 4 by the author

Samenvatting

In de jaren ’60 kwamen in het Gooi nog wrattenbijters

(Decticus verrucivorus) voor, verdeeld over 2 popula-

ties met elk zo’n 100 zingende mannetjes. Deze dieren

hadden minimale afmetingen en waren vrijwel altijd

van een donker-blauwgroene kleur. Het analis-cubitalis

foto of veld (a, 5) was eveneens donkergroen, zeer don-

kerbruin. Toen ik in 1981 tijdens een bezoek aan het

Deense Hanstholm reservaat dezelfde kleurvariëteit van

kwam ik de de wrattenbijter aantrof, tot hypothese van

een ‘atlantische vorm’, die kustheiden van Noordwest-

Europa zou bewonen.

In 1992 moest ik deze veronderstelling laten vallen: in

dat jaar bezocht ik grote delen van het schiereiland Thy

en hoorde duizenden wrattenbijters sjirpen. Ze kwamen

in verschillende biotopen voor, waren heel gevarieerd

van kleur en hadden behoorlijke afmetingen. Dieren

met een blauwgroene kop en pronotum werden, naast andere variaties, echter uitsluitend in de heidehabitat

aangetroffen (bijlage 1).

dit ik In artikel probeer de zeer karakteristieke Gooise

dierente duiden als aanpassingen aan een zeer eenzijdi- Figuur 1. locatlon studied sites: A. Gooi (Nl), B. Thy (Den.)

ge habitat, nl. de dofgroene, door menselijke invloed ontstane struikheide-akker (Genisto anglicae-Callune- tatie, die, als de schapen enige jaren geleden het

De vallen hierin min- betreffende bezocht tum). donkergroene wrattenbijters perceel hebben, over grote opper- der op dan de lichtgroen gekleurde. Feitelijk bestaat het vlakten tot gelijke hoogte is uitgegroeid (foto 1). Dit biotoop van de wrattenbijter uit twee habitats, één voor laatste is erg belangrijk, want hier hebben de mannetjes de larven één de volwassen dieren De hun en voor (tabel 1). baltsplaatsen (‘leks’): ze leggen er afstanden van larvale habitat is begroeid met een nogal vochtig, licht- wel 100 m per dag af, om met elkaar te rivaliseren en

afwisselend groen gekleurd vegetatietype, dat van wijfjes te ontmoeten. Het belang van een strukturele hoogte en rijk aan struktuur is. In het Gooi wordt de hoogte van de vegetatie ca. 25 cm boven de bodem is, adulte habitat gevormd door uniforme struikheidevege- dat de dracht van het mannelijke gesjirp in dat geval

10 Nieuwsbrief Saltabel 8 (1992) het meer dan twee maal zo groot is dan op de bodem zige vegetatie met gedeeltelijk afgestorven grasbladen

bv. zou zijn. Vergrassing van de heide door bochtige smele bevindt, een helmgrasvegetatie (Elymo-Ammophi-

(Deschampsia flexuosa ) hindert de dieren in hun voort- letum). De uniforme donkergroen-bruine analis-cubita-

beweging, en dit is waarschijnlijk de voornaamste oor- lis velden van de Gooi-dieren zullen een aanpassing

Calluna zaak geweest van het uitsterven van de wrattenbijter in zijn aan het eenzijdige dofgroen gekleurde

het Gooi in 1989. vulgaris- biotoop.

In Noord-Jutland zijn zowel de habitats voor de volwas-

sen wrattenbijters als die voor de larven veel gevarieer- 1. Introduction

der dan die in het Gooi (par. 3.2 en foto’s 2-4). Dit is In the 1960’s hundreds of wartbiters occurred in the

vinden in het divided the terug te uiterlijk van de dieren (foto’s 5- Gooi area, among two populations, one at

10). North and the other at the South Heath. The species is

Het biotoop van de wrattenbijter stelkt complexe eisen, since 1989extinct in the Gooi. bovendien the I took the heeft een gezonde populatie een nogal groot According to notes and 30 specimens or

Daardoor het dan ook that I the from these oppervlak nodig (par. 2). gaat so collected, two arcas

and, slecht met deze gorilla onder de sprinkhanen in het were very conspicuous: they were very small,

coloration. geciviliseerde Noordwest-Europa. De populatie op Thy when green, in all cases of a dark blue-green

is thans de belangrijkste van deze regio. The analis-cubitalis field (a, Photo 5) at the upper edge

Ca. 5% de dieren is colour van Gooise niet groen gekleurd, of the elylra was either ofthe same dark green or

maar geheel of gedeeltelijk zwart, grijs, bruin of paars. very dark brown, never pale brown, reddish brown or

Voor populaties in andere biotopen gelden vergelijkbare yellow, like in the photograph of this species in Duijm

lateral getallen (Sussex: kalkgrasland; Thy: gevarieerde duin- & Kmseman (1983). The black stains on the

vegetaties: tabel 2). De naar mijn inzicht meest bevredi- lobes of the pronotum (b) and elytra (c) and the lines on

in gende hypothese voor dit verschijnsel is, dat selektieve the abdomen (d) were more developed than many

die zich predatie van de larven, immers in een groene Continental specimens.

all the habitat bevinden, een groterol speelt Except for one, incompletely labeled specimen,

is het de the Aantrekkelijk werking van epistatische genen wartbiters from the Gooi present in Entomological

veronderstellen, dx. dominante die of Amsterdam have these te genen door hun Museum of the University

invloed op meerdere loci een (te?) grote variatie binnen features. They are not only collected by me, but were

de bruine Piet and Troelstra populaties tegengaan. Bij sprinkhaan (Chor- also by, a.o. MacGUlavry, Kmseman,

thippus brunneus). waar deze genen zijn beschreven, bctween 1915 and 1967. All my specimens, and suppo-

habi- kunnen ze m.i. populaties van deze soort ‘beschermen’ sedly theirs too, have been collected in the heath

veel in hoewel toch Hanstholm Reserve in tegen te variatie basiskleur, een tat. In 1981 I visited the

schier eindelozeafwisseling in kleur bij een minderheid Northern Jylland (Denmark). Here I found wartbiters

de De dieren of van populatie mogelijk is. kunnen daar- with the same coloration, but ‘normal’ dimensions door leven in biotopen met een zeer verschillende kleur (Photo 5). I arrived at the hypothesis of a special

klein aantal is inhabit Coastal heath en structuur, terwijl een aangepast aan ‘Atlantic form’, which would

microhabitats. bepaalde arcas in NW Europe (Tienstra, 1992).

Voor de het of this ha wrattenbijter, waarvan mannetje dagelijks After I visited the SE part magnificent 6000

maakt in in the 1992 the grote afstanden loopt en dat gebruik van vegeta- Reserve 1981,1 explored summer of

of State and the the ties van verschillende kleur en struktuur, zou te grote NW part the Reserve area between variatie binnen een populatie, analoog aan Chorthippus Reserve and Frpstrup, part of the peninsula of Thy. I brunneus, nadelig kunnen zijn. heard the chirping of at least several thousands of male

Decticus verrucivorus. In a number of places the popu-

De kleur het in van analis-cubitalis veld heeft waarschijn- lations of the inland and Coastal biotopes are still lijk de funktie dat hierdoor het dier a.h.w. visueel in contact witheach other. My observations here made me

wordt tweeën gedeeld en derhalve minder als zodanig drop my hypothesis: the dark-green Gooi wartbiters herkenbaar hierar- is voor predatoren, vooral als dit vleugelge- cannot be classified into a higher ‘Atlantic form’ deelte is geelachtig gekleurd en het dier zich in een gra- chy.

NieuwsbriefSaltabel 8(1992) 11 discus- ments. In this article the colourof the wartbiters willbe

Gooi As the propagation of the sound of the wartbiter is sed in relation to the biotopes in the and Thy. very

- of 2-3 it poor at ground level at a distance m. provokes

- structural no longer a reaction of its a vege- 2. Biotope conditions opponent the of consists of tation of 20-25 cm. high improves transfer The biotope of Decticus verrucivorus two layer

for the adult ani- the of the wartbiter’s habitats, one for the larvae and one high frequencies walking chirp up

4-5 and further et mals. The larval habitat is formed by a high-structured to m. (Keuper al., 1986).

the that consists of several layers between For this uniform anthropogenic Genisto green vegetation purpose

here also takes in (see de Smidt, 1981) 0 and 55 cm high: oviposition place anglicae-Callunetum-vegetation

with a of the Gooi is fit. When a flock of sheep patches of bare sand or in those covered very (Photo 1) very

several all the heat- thin vegetation (own observation, see also Cherrill & grazed a particular area years ago,

thus will to the same making Brown, 1990b). As the diapausing eggs starve her-plants grew out height,

wartbiters is the of the at a con- below a humidity level of 75% (Ingrish, 1986), it possible daily wanderings

the soil is humid here all over stant distance from the ground. absolutely necessary that

this bushcricket has small fore and also when it seems on the face of it, a con- Though large very the year: dry

- avoid obstruction a from cm midlegs to by grasses -, stant humidity at a depth 3 on is indispensable. probably

be far from and the flowering Adult females can mostly found not very too grassy habitat, especially rigid these ‘larval’ places, but in fact the exact distribution of sterns of the grass Deschampsia flexuosa, may impede

as its tours and thus its sexual (rivalry) con- the females during their life cycle is unknown: they daily walking

the males find themsel- detect them in the field. tacts. Therefore, in places don’tchirp, it is not easy to many

for their the here 100 m ves in areas leks, vegetation being The adult males walk, while chirping, up to a dry

the the scattered behaviour. This wal- so scarce that can wander, using daily, as part of their sexual rivalry they

where some tussocks of the Corynephorus canescens as a king takes place in well-defined areas, e.g. grass ‘structural’ males meddle with each other. These In the Thy dunes a vegetation twenty to thirty chirping post.

number of leaves of the Ammophila ‘leks’ (Wilson, 1980) have to meet a of require- layer flat-lying dune-grass

this has function for the leks of the wartbiter. Photo 1. The Gooi, South Heath, 1964. Genisto anglicae-Callunetum. vegetation a Lande 1964. ofthe larvae be seen.Le Gooi, mériodionale, In the distance, 30 m. lower, the humid ‘ green’ breeding places can

certaine foncton les “leks'. A 30m bas, le Gentsto anglicae-Caltunetum; cette vegetation a une pour l’arrière-plan, plus biotope humkJe des juvéniles.

12 Nieuwsbrief Saltabel 8(1992) arenaria is also used as such.

larval habitat tarval habitat Bccause of all these conditions the leks can be found at VofQdVarnaof cycl*cycle tfsckütrack: small flxed places. In most landscapes only a very part Sttlelittle holahole that coBects rainrain water from trade;track; helghtheight of

vegetationvégétation 0*10-30 cm, coveragacoverage about90%. of an extensive area is used by the wartbiters: they not

only need lek territories with a not to luxuriant Orthoptera vegeta- Main plant species5 oSc^verrucivorus Decticus verrucivorus tion, but also humid places for deposition and AgrostisJJSsfeSSScapillaris egg virkhssimaviridissima lanceolatalanceolate Tettigonia Plantago ‘green’ vegetations for larval development in their Chorthippus brunneus Campanula rotundtfoBarotundifoka C. moitis neighbourhood. Dactylis glomerata C. aibomarginatus If I the that minimum of 50 60 chir- «aas*Hotcua lanatus put case a somc to Grytlus campestris Mofinia caerulea Gryllus ping males, to be divided among 2-5 leks, and which Galium mollugo mutually can enrich the populations of each other as to TrlfoliumTrifolium repeosrepens Cirsium arvensa their genetica! composition, is necessary for the long- Artemisia vulgaris term survival of the wartbiters, then the ‘vital space’ Rubus Cf.cf. fruticosusfruticosus

(Lensink, 1963) in the more uniform landscape of the

Larval and aduitadulthabitat Gooi area is 1,5-2 sq. km and in part of the Thy dunes, Souteast exposed slope of loam pit, veg. Festuco-

with the highest of variation, 4-5 as I obser- ThymatumThymetum serpylltserpylli (Westhoff & danden Held. 1969)1969) degree ha, of 0-3-15-25-35-55 height vegetation: cm,cm. coveragacoverage ved in the field in the respective areas. 95% The maximum diameter of a large lek is about 150 m:

Mainplant species Orthoptera in the Gooi, where the larval areas were situated espe- Calamagrostis epigejos DecticusDacticus verrucivorus cially along paths etc., the distributionof the leks also HyperkmmHypericum perforatum Chorthippus brunneus created linear with a maximum of 3 km; Agrostis capillaris C. biguttulus figures length Festuca rubra C. mollis in the differentiated Thy dunes the usage of the area by FestucaFéstuca ovina Omocestus viridulus the wartbiters can be more economical, so that the vital Ononis spinosa Stenobothrus stigmaöastigmaticus Nemobius Pimpinelia saxifragasax ifrag a sylvestr»sylvestris space can be smaller here. Nevertheless, this is also a Thymus serpyllumsarpyllum large area for a ground-dwelling . Polygala vulgaris On of the conditions mari,imUmmaritimum aacoount complex biotope the Galiumünïrca?Scum’verum ssp. Unum catharticum wartbiter has strongly declined in NW Europe, especial- Lotus corniculatus ly in the last two decades, in several countries nearly to Viola canlnacanina

CallunaCaüuna vulgaris extinction. The Thy populations undoubtedly is the

ErigeronErigoronaceracer most important of the region. Antennaria dtoica

AdiilleaAchillaa millofoliummillefolium

lanceotatalanceolate PtantagoPiantago 3. The biotopes in the two areas

AduitAdult habitat(used(used as lak):lek): 3.1. in the Gooi veg. Genisto anglicae-Callunetum (Photo 1)1) The biotope (Photo 1) and height of vegetation; uniform 0 30 cm, coverage 80% In the 1960’s the wartbiters exclusively used a small

Main plant species Orthoptera species part of the 1000 ha grey-brown podzolic soil occupied DacticusDecticus verrucivorus CaüunaCalluna 80%) uniform Genisto Chorthippus b.guttulu* by a anglicae-Callunetum vegetation, Genista anglica Chorthippus biguttulus Myrm. macuiatus GG. pilosa a result of five ages of human wood cutting and sheep

0ödOed.- caerulescens Festuca ovina ssp. animals had their grazing. Here the leks. These were tenuifotia the larval which Nardus stricta situated near ‘green’ places, were lying

flaxuosafiexuosa Deschampsia (rare) either along the main cycle track, where water from the 'min open placesplaces a.o.;a.o.: track was led into undeep holes and ditches, or in loam CiadoniasCladonias

Polytrichum piliferum pits (Table 1): very vulnerablelocalities in the crowded Dicranum scoparium Gooi area because of tourist recreation, and even more

in as these were very limitcd areas the monoculture of Tabla 1. Exampfas of larval and aduit habitats of Decticus Calluna verrucivorus in the Gooi; #ie main plant species and the vulgaris.

Orthopterafauna In the localities (data; Tionstra, 1992).

Biotope de Decthus verrucivorusau Gooi.

Nieuwsbrief Saltabel8 (1992) 13 3.2 The biotope at Thy (see for the Orthopterofaunas gare, Hieracium umbellatum and Ammophila arenaria.

Appendix 1) Scattered over the arca you can find many low, grassy

places with a.o. Calamagrostis epigejos, Pimpinella

3.2.1 Coastal heath (Photo 3) saxifraga, Ophioglossum vulgatum and in the weitest

In Denmark the natural heath habitat, consisting of places, unfit for the wartbiter, Hydrocotyle vulgaris,

Carici arenariae-Empetretum (de Smidl, 1981) has a lot Orchidaceae div. spec. and Gentianapneumonanthe.

it for in the border of variety: conlains, except Carex arenaria and I suppose that egg deposiüon takes place

Empetrum nigrum, plant species like Polypodium val- zones of these small areas, where a.o. Plantago corono-

pus. Armeria maritima, Ononis spino-

sa and Odontites verna indicate a form

of Plantago coronopus-Carex distans-

association (Westhoff & Den Held,

1969). On the bare, sandy ridges of the

soil here the females maydeposit their

indicates eggs. This vegetation also

that the water level is rather high.

3.2.2. Coastal dunes (Photo 3)

The same can be said of the Coastal

dunes, where the wartbiters occur in

densities. Here greater population too,

the soil is always moist and males as

well as females can be found in the

superficially uniform-looking vegeta-

tion, which however demonstrates a

subtle, nearly mosaiclike diversity; the

dunes on the weather side are covered

with an Elymo-Ammopliletum-vegeta-

tion, var. with Elymus arenarius and

Lathyrus japonicus (= maritimus) (low

population density of wartbiters)

and off the wind side with the variety

with of this plant-associaüon a.o.

Festuca rubra, Hieracium umbellatum

with patches of Carici arenariae-

Empetretum and Violo-Corynephore-

in tum (Westhoff & den Held, 1969)

between (very high population den-

sity of wartbiters); in Appendix 1

these lee side plant-associations are

presented together under the heading

Photo 2. Thy, 1992, Inland heath near Frastrup: a mosaic of patches with a.o. ‘Carici arenariae-Empetretum ( + Vaccinium uliginosum, Calluna vulgaris, Empetrum nigrum with Ammophila are- Ammophiletum aren.. etc )’, so to tetralix. A littie the flexuosa The naria, Erica ‘spoiled’ by grass Deschampsia be considered of the heath population density of the wartbiters is small in the heath, as compared to that in as part the of verge of the road (front photo), which functions as a corridor between habitat heath areas. Thy, 1992. Lande prés de Frastrup: végétation mosaique de The leks SE Vaccinium uliginosum, Calluna vulgaris, Empetrum nigrum, Ammophila are mostly on exposed arenaria, Erica letralix. Une partie est envahie Deschampsia flexuosa. La par slopes, often with an Ammophiletum- densité de la population de Decticus verrucivorus est petite dans la lande, en comparaison avec Ie bord de la route, qui fait fonction de corridor entre deux vegetation. parties de la lande.

14 NieuwsbriefSaltabel 8 (1992) and Violo- Photo 3. Hanstholm Reserve, 1981. Coastal heath and dunes. A mosaic of Elymo-Ammophiletum, Carici arenariae-Empetetrum

most can be found in SE exposed On the lefl in the dis- Corynephoretum functkxis as a walking area tor the male wartbiters; leks Ammophiletea

to fit tor larval wartbiters. Landes et dunes k la cöte. de Elymo-Ammophiletum, tance a ‘green'place, which I suppose be Végétation mosaique les mêles. La des ‘leks’ Carici arenariae-Empetrum el ViotoCorynephoretum fait fonction d'aire de ‘promenade’ pour plupart se trouvenl sur

des Ammophiletea,exposés au sud-est A gauche une zone ‘verte’, biotope juvéniles.

Urtica dioica; It Photo 4. Thy, 1992. Verge of road 6 km. eats of Hjardemèl. Dry ditch with a.0. Heracleum spondylium, Equisetum arvense, next to females in linear scanty (ormer 'produclive' grassland. In the area in-between, parallel to the wire, chirping males and (egg-lying) a configuration. Unica dioica A cóté: abandon- Bord de route, 6km è l est de Hjardemèl. Fossé sec k Heracleum sphondylium, Equisetum arvense, pelite pelouse nóe. Entte les deux, males chantants et femellespondants sur une ligne.

NieuwsbriefSoltdbel8 (1992) 15 the social structure of the lek must have been weak, also v -, . || , , v Sussex population (chalk grassland) because the males were chirping here at soil level, a (CherrSI & Brown, 1991) males and females unfavourable condition with very acoustic properties. 1987 95.2 (n-334)

1988 86.5 (n*266) In many places however these long anthropogenic 1989 1 00 (n-201) structures have a function as corridors between distinct

areas. GooiGool popuiationpopulation (dryCallunetum)Cattunetum)

own observatoria,observations, onlyonly malesmates 1966 93.4 1966 (n-91) 4. Colour variation in the two areas 19671967 94.5 (n-73)

1969 100 (n-63) 4.1 The Gooi

The colorationof the green specimens was described in

2. of animals in Tabte Pecentage green (adult) two popu- par. 1 of this article. A small percentage of the adult tations of Decticus verrucivorus. Pourcentage d'adutte de wartbiters did not have the overall blue-green colour. couleurverte dans deux populatlons de Decticus verrud- This with that of the Sussex- vorus quantity globally agrces

population and the Denmark-data (Appendix 1).

I found the following not-green varieties: 3.2.3. Inland heath(Photo 2) - sides of the animalpale grey (upper side of head, pro- On the more inland heaths vegetation is denserand hig- notum and elytra, including analis-cubitalis field, her; the Calluna vulgaris and Empetrum nigrum plants blue-green) 45 ‘ideal’ for the wal- are up to cm high (the height

- animals of overall dark grey, nearly black coloration king/chirping maleDecticus’ is about20 cm, par. 2). - overall purple The vegetations are often mixed with the grass - overall pale brown Deschampsia flexuosa, of which, as stated above, the

- overall reddish brown rigid flowering sterns impede the males in their daily

- overall darkbrown walking tours to challenge the other males and to meet All colour variations demonstrate the characteristic

females. So this grass, the result here of the decline of white stripe, with black and mostly also white spots on wind influences because of P/niw-plantations, and the the elytra. I collected specimens of most varieties. As I end of sheep grazing, directly destructs the structure of prepared them with formaldehyde 10% they maintained in with the lek. All the heath areas north Jylland more their well. colours pretty than approximately 30% Deschampsia had no wartbi-

ters at all. 4.2 Thy Another cause of their absence may be the fact that the In 1992 I didn’t find specimens with an overall blue- areas of bare soil are minimal here, so that the females like those of 1981 visit and green coloration my as cannot deposit theireggs. described in par. 1 (Photo 5). Nevertheless, in the area I

visiled this summer animals with blue-green head and 3.2.4. Road verges (Photo 2 and 4) but with coloured could be pronotum pale green elytra Where wartbiters in inland heath areas do occur, they found (Photo 6). This variation however was only pre- can be found in anthropogenic biotopes, like the road sent in the heath habitat, while I saw all-over pale green verge of Photo 2, respectively on the edge of a Poo- wartbiters (Photo 7) in all habitats. The colour of the Lolietum (Westhoff & den Held, 1969), a former ‘pro- analis-cubitalis field at the upper edge of the elytra (a, ductive meadow’ (Photo 4), which, as a consequence of Photo 5) was, of the animals from the heath, as well as poverty of the soil and a dry spring, looks more like a those from the other habitats, green, pale brown or dark savannah vegetation at the end of the dry season. I brown (Photos 5-10). A good number of specimens had

foundchirping males here in a linear constellation, bac- lateral lobes for the ‘traditional’ pronotum with, except ked by the high herbs of the dry ditch. On this ridge olive ditto coloration black spot, an brown or green (a, long, sandy patches, tracés of former ploughing, could Photo 8). This feature was always coupled with a fron- be seen. In this place I observed an egg-lying female. tal the hind femora in this olive colour spot (b) on set- As a consequence of the linear position of the animals

16 Nieuwsbrief Saltabel8 (1992) ting, which is an argument for linkcd genes or plciotro- (Rubztov, 1935). Both phenomena togethcr enhancc the

fitness py- of these populations, as they are better able to

I saw one specimen of an overall dark brown coloration exploit their environment than monomorphic popula-

(Photo 9). tions.

The exclusively (?) blue-green coloration of the Gooi-

5. Discussion wartbiters in green coloursetting might lead to the con-

clusion that amputation of their biotope on account of

5.1. Varieties in the green body colour the building of houses upon the communal meadows at

of the wartbiter the the end of the last and the of this The biotope at Thy is, including beginning century led heath habitat, much more varied than that in the Gooi. to gene flow and consequently to impoverishment of

The presence and/or lack of distinct body colour varie- the gene pools of the populations. The usual lag ties in these areas must be considered as selective ans- between the state of the environment and the adaptive wers to their respective circumstances. state of the population had probably become substantial

Investigations of a number of Acrididae demonstrate in the Gooi area, so that the animals must have been the importance of a large phenotypic variation for vulnerable. Although the Gooi populations had accom-

of this maximum ground-dwelling grasshoppers, as vegetations plished crypsis because of the development

variable in of overall dark colour in all indivi- biotope are spatially and temporally very our an blue-green nearly climate. Moreover, grasshoppers with a large phenoty- duals-, they were however still conspicuous in the dull- pic variation have been demonstrated to choose actively green Calluna vulgaria-habitat, at least to human eyes. for habitats that agree with their own body coloration Nevertheless, the flossy purple inflorescence seemed to

Photo 5. Hanstholm Reserve, 1981. All-over dark blue-green male of Decticus verrucivorus. The elytra with the anaHs-cubltalls field (a) also have

this coloration;the black spots on latera! lobes of pronolum (b) and elytra (e) are well-developed, as well as the black striping (d) on the abdomen.

Male vert foncé de Decücus verrvcivorus. Les élytres et Ie champanal-cubital (a) de mème coloration:les lèches noires sur les lobes du pronotum

(b) et sur les éluytres (c) sont bien développóes, de même que les anneaux noirs sur l'abdomen (d).

Nieuwsbrief Saltabel 8 (1992) 17 and of Photo 6. Frastrup Heath, 1992. Male of Decticus verrucivorus. Animals from the heath are often smaller, more markedly stained and striped

darker than those trom olher sides of and abdomen; dark latera) lobes of and front a green biotopes. Head, upper pronolum blue-green; pronotum of hind femora olive Decticus verrucivorus. Les animaux vivant les landes sont brown; elytra green; analts-cubitalis field pale brown. Male de sur

de couleur celles des du et abdomen vert foncé; lobes du plus petits, plus fonoée, que autres biotopes. Tête, partie supérieure pronotum pronotum et fémurs postérieurs buns olives; éfytres verte; champ anal-cubital brun clair.

Photo 7. stained and all-over female of Decticus verrucivorus found in This weakly striped, pale green was a dry Callunetum-vegetaion near Femelle Frestrup. de couleur verte claire vivant dans une végétation de Callunetum.

18 Nieuwsbrief Saltabel8(1992) Photo 8. male of the of 4. The wartbiters In these somewhat and have colo- Hjardemél, verge photo biotopes are mostly bigger a more pale green

ration. Colour: overall also the analis-cubitalls latera! lobes of and front of hind femora show the characteristic for green, Held; pronotum (a) (b) (so

the Thy peninsula) olive brown coloration.n male du bord de route de la photo 4. Les animaux de ce biotope sont plus grands et de couleur plus

claire. Coloration: vert, également Ie champanal-cubital; lobes du pronotum (a) el fémurs postérieurs (b) brons clairs.

Photo 9. Hanstholm Reserve, 1992. This big male was found in the first line of sea-side dunes, in Ammophiletum. Overall body colour dark brown, except for analis-cubitalis field (pale brown) and lateral lobes of pronolum/front of hind femora (dark olive brown). Ce grand mêle a été observé

dans la de dunes dans Coloration: brun è du anal-cubital première rangée cótieres, un Ammophiletum. corps foncó, l'exception champ (brun clair) et des lobes du pronotum et des fémurs postérieurs (brun-olive foncé).

NieuwsbriefSaltabel 8(1992) 19 Photo 11. Hjardeméü Klit, 1992. This big female was found near to the male of photo 9. However, it fiew offwhen disturbed and covered some 15

m in a nearty horizontal line. Colour; overall pale green, except for the analis-aibitalis field (pale brown); black staining and stripes at pronotum, elytra and abdomen minimally developed;one hindleg missing. Cette grande femelle a été observée prés du méle de la photo 9. Elle s'envolait

sur une distance de 15 m. Coloration: vert dair, a l'exception du champ anal-cubital (brun foncé); cloration foncée et taches sur Ie pronotum; élyt-

abdomen res et peu développés; une patte postérieure manque.

favour crypsis. Also in Denmark the animals with a beak marks on her abdomen. In Denmark birds of prey

(partly) blue-green colorationwere probably - the mate- seemed to be nearly completely absent at the moment, I rial is statistically insufficiënt - restricted to the heath suppose as a consequence of the intensive com culture

habitat. The 1992 findings in this habitat were made in over extended areas.

300 from dunes other Besides mammals the lizard Lacerta which places up to m or ‘green’ vegeta- big ( agilis),

tions. The overall blue-green specimens of my 1981 is very common at Thy, may be a potential predator.

visit to the Hanstholm Reserve occurred in a large heath

area, 3 km removed from Coastal and ‘green’ vegeta- 5.2. Percentage ofa not-green basic body coloration

tions like road verges, meadows etc. In par. 4 (Table 2) I pointed out that a minority of adult

These observations led me to my selection hypothesis specimens from the Gooi, Sussex and Thy populations

conceming the blue-green Gooi animals. didn’t have the overall blue-green, green or pale green

Ofcourse predation of adult individuals by vertebrates body colour. I suggest that this may have to do with

must play an important role in this, but I honestly admit predation of the larvae. Just after hatching the larvae

that my own observations of predation are scarce: in the have a greyish coloration (Cherrill & Brown, 1991).

Gooi the sparrow hawk (Accipiter nisus) skims over the During their development they generale the green

heath, catching , but I didn’t collect concrete colour more and more, especially from stage 4 on.

data. While they find themselves in their green larval habitat

Cherrill & Brown (1990b) report the kestrel (Falco tin- during this period, selective predation of the not-green

nunculus) as a potential predator. colour varieties seems likely. In any case the mortality

They record 5.2 % of the adults of the 1987 Sussex- rate of the larvae is very high; in the 1988 Sussex-popu-

population with severed hind femora, hindtibiae or ovi- lation 99.3 % ! (Cherrill & Brown, 1990a). Candidates

positors; a further 13.0 % had an entire hind leg mis- for this feat might be the crested lark (Galerida

sing, while an adult female was found with triangular cristata), the wheatear (Oenanthe oenanthe) and groups

20 Nieuwsbrief Saltabel 8 (1992) of wandeling starlings (Sturnus vulgaris). Although 5.3. Colourof analis-cubitalis field

occurring in the area then, I never saw the black grouse The colourof the analis-cubitalis field at the upper edge

and the Phasanius (Lyrurus tetrix) pheasant ( colchicus) of the elytra undoubtedly plays an important role in

of the in the neighbourhood breeding places, contrary to crypsis. When the is in a resting position, the

samll lizard Lacerta clear lateral the ( vivipara), which is very com- green sides are not easily visible. Seen

mon in the Gooi as well as in the Thy area.. from above, the brown colour of the area mentioned

the data of the and favours of the animal Considcring Gooi, England crypsis in more luxuriant grassy

which the of it in the form of Denmark, agree as to percentage green vegetations, as presents itself a linear

individuals in these populaüons, predation of adult structure. Becau.sc of this the rectangular form of the

wartbiters not role in the may play an important 95/5 green pronotum and head may look less conspicuous, as

body colourratio. the animal is, so to say, divided in two clements.

Another possible explanation for this might be the wer- In the dull dark green Calluna vulgaris-monoculture.

which king of epistatic genes, i.e. dominant genes that exhibit was formerly so abundant in the Gooi heaths, a

with dark or interactions other loei, thus ‘protecting’ the popu- green dark brown an.-cub. area would favour

lations of the wartbiter from too much variation and crypsis, a pale colour ed one would make the animals

nevertheless making possible an enormous variation in very conspicuous. This might explain the complete (?)

of the a minority of it (analogous to Chorthippus parallelus absence pale brown colorationof this area in the

(Sansome & La Cour, 1935) and C. brunneus (GUI, individuals of the Gooi populations, according to my

1981). One may imagine that maximum crypsis for a own observations and as demonstrated by the material

Decticus collected in is in number large bushcricket like verrucivorus, which Amsterdam, while it present a

occupies habitats of diverse colours and structures (e.g. of the Jylland wartbiters, as well as in those from other

the colour and diameter of leaflels in poor vs. more Dutch populations (e.g. Hoge Veluwe, Nunspeet,

luxuriant vegetations), will be realised by not too much Drongelen, Hoog-Buurlo). The biotopes in these places

variation. The males of this species walk around in the are more varied in structure and colour of vegetation

sunshine, while chirping, covering distances up to 100 than that of the uniform Calluna-habitat in the Gooi,

m a day. During these activities they make use of diver- which became nearly the only open type of vegetation

until se vegetations (see also Photos 1-4), in which a not- in this area the 1970‘s, when the expansion of the

coloration be and of the exoüc Prunus greenbasal might disadvantageous. grass Deschampsia flexuosa

Crypsis with less uniformity is to be found with little serotina had begun, results of increased N-deposition

like maculatus which grasshoppers Myrmeleotettix pre- and the end of sheep grazing..

sents an almost endless varicty in body colour and The variety in colour of the analis-cubitalis field in the detailed spotted and striped markings. This small xerop- Jylland populaüons (Appendix 1) is certainly correlated hilic grasshopper, occurring exclusively in the heath here to the diversity of biotopes and a certain disequili- habitat, is, in its variety, very well adapted to many brium of the regulaüng genes. microhabitats of the heath biotope, where it dwells all its life. 5.4. Black staining and stripes

in Chorthippus brunneus however, which can be found The black stains on pronotum and elytra, and ditto lines

of has brown the a variety biotopes, predominanüy a body on abdomen also can be considered as adaptaüons

other colour demonstrated with funcüon of this colour; varieües are only by a crypsis ground-dwelling bush- a minority in most populaüons as adaptaüons to speci- cricket. I could not find a significant difference in the fic microhabitats, thus enlarging the fitness of these amount of staining between ‘heath’ and ‘green’ habitat populaüons as a whole. In this species the working of animals (Appendix 1). epistatic genes has been confirmed (GUI, 1981).

Decticus verrucivorus lives in habitats with a large 5.5. Geneüc characterisücs of respecüve colourfeatures diversity too. An analogous hypothesis can be offered Stains on elytra and body, and also the (for the Danish

forthis wandeling insect specimens rather typical) combinaüon of dark olive

brown lateral lobes of pronotum and olive brown stains

hind femora on ‘shine through’ the green basic colour.

Nieuwsbrief Saltabel 8 (1992) 21 the these AJ. & V.K. 1991. colora- Even in brown, grey, violet, etc. specimens Cherrill, Brown, Variation in

features are visible. This argues for different gene com- tion of Decticus verrucivorus (L.) (Orthoptera;

plexes of these genes respectively: the overall body ) in southem England. Entom. Gazelle

colour is superimposed on other polychromatic varia- 42: 175-183.

tions in detail. Duijm, M. & G. Kruseman, 1983. De krekels en sprink-

hanen in de Benelux. Uitgave KNNV 34: 1-186.

5.6. Altemativehypotheses GUI, P.D., 1981. The genetics of colour patlems in the The basic body colour, notably the adult (blue-)green, grasshopper Chorthippus brunneus. Biol. J. Linn. might, besides genetic and selective correlates, be the Soc. 16: 243-259. result of modification.Young wartbiters have a greyish Ingrish, S., 1986. The plurennial life cycles of the coloration; during their larval development they genera- European Tettigoniidae (Insecta; Orthoptera). 1986 le their green body colour. c 3. The effect of drought and the variable duration Laboratory experiments with Schistocerca vagans of the initial diapause. Oecologia 70: 624-630. demonstrated that low humidity during earlier larval

Keuper, A., K. kalmring, A. Schatral, W. Latimer & W. stages result in a high proportion of green hoppers tur-

Kaiser, 1986. Behavioural of ning brown in later instars, whereas high humidity adaptations ground

living bushcrickets to the properties of sound pro- result in most hoppers retaining their green coloration pagation in low grassland. Oecologia 70: 414-422. (Rowell & Cannis, 1972). Analogous to this, the young

larvae of the Gooi wartbiters may have generaled a dar- Lensink, B.M., 1963. Distributional ecology of some

ker green body colour during their development in dis- Acrididae (Orthoptera) in the dunes of Voome,

tinctly drier habitats than the Jylland animals in what I Netherlands. Tijdschr. Entom. 106: 357-443.

to be their ‘breeding areas’. suppose Rowell, C.H.F., 1971. The variable coloration of acri-

Homochromic i.c. grasshoppers developing responses, doidgrasshoppers. Adv. Insect Physiol. 8: 145-198.

pigments within a very short period so that they can Rowell, C. H. F. & T. L. Cannis, 1972. Environmental

survive at a substratum whose colour has suddenly factors affecting the gneen/brown polymorphism in changed, e.g. after a fire, can be excluded for the wart- the cyrtacanthacridine grasshopper Schistocerca biter. This phenomenon only seems to involve black, Acrida 1: 69-71. vaga (Scudder). yellow and orangc pigments and apparently these are Rubtzov, I.A., 1935. Phase variation in non-swarming not produced on green backgrounds (Rowell, 1971). grasshoppers. Buil. Entom. Res. 26: 499-574. Moreover, the greyish colour of the young Decticus lar-

F.W. & L. 1935. of 4 the larvae still Sansome, La Cour, The genetics vae changes to green from stage on, as

grasshoppers; Chorthippus parallelus. J. Genet. 30; find themselves in their green larval habitats.

415-422.

Acknowledgements Smidt, J.T. de, 1981. De Nederlandse Heidevegetaties.

I am grateful to Sietso Jan Nanninga for editing the Wet. Meded. KNNV 144: 1-87.

English texL Tienstra, R., 1992. De zwanezang van de wrattenbijter

(.Decticus verrucivorus (L.); Insecta: Orthoptera) in

het Gooi, een kroniek van 1966-1991. Fenologie- References ecologie en fysiologie-sociobiologie.

Cherrill, AJ. & V.K. 1990a. The life and Brown, cycle last of the wartbiters in (The song the Gooi, a chronicle

distribution of Decticus verrucivorus within a (L.) from 1966-1991): unpubl. report: 75 pp. chalk grassland in Southem England. Biol. Westhoff, V. & A.J. den Held, 1969. Plantengemeen- Conserv. 53: 125-143. schappen in Nederland. 342 pp. Thieme, Zutphen. Cherrill, AJ. & V.K. Brown, 1990b. The habitat requi- Wilson, E.O., 1980. Sociobiology (the abridged edi- rements of adults of the wart-biter Decticus verru- tion): 366pp. Harvard/Cambridge, Mass. London. civorus (L.) (Orthoptera: Tettigoniidae) in Southem

England. Biol. Conserv. 53: 145-157.

22 Nieuwsbrief Saltabel 8 (1992) Résumé

Deux populations de Decticus verrucivorus, une du Gooi

(Pays-Bas) et une de Thy (Danemark) ont été étudiées. Au

Gooi, presque exclusivement des animaux verts foncé ont

été observés, tandis qu’à Thy il y avait plus de variabilité

dans la coloration de l’animal (vert clair, vert foncé, brun

olive) et des élytres (champ anal-cubital), mais la propor-

tion d’animaux verts est également 95%. Les animaux du

Gooi étaient également de taille extrêmement petite, ce

qui est probablement du au biotope peu varié, consistant

d’une lande à Calluna. A Thy, les animaux volaient faci-

lement. L’espèce est en déclin dans le nord-ouest de

l’Europe. La population du Gooi n’existe plus depuis

1990. Celle de Thy est probablement la plus grande de la région.

NieuwsbriefSaltabel 8(1992) 23 Appendix 1

ofDecticus Data verrucivorus from northem Jylland, collected by R. Tienslra, august 1992

Doimées concemam Declicus verrucivorus dans le nord de Jylland en aout 1992.

‘green’ habitat

sex pronotum elytron hindfemur color lat lobes black stains elytra color an.-cub locality ovipositor body pron.

9.0 23 32.5 d. brown A a green +++ p.

- d. brown B a 9.0 30 32 green +++ p.

8.5 28 28 d. ++ A brown C cf green

8.5 31 31 D a p. green +++ p. green

a 8.5 31 32 + brown D p. green p.

9.0 33 34 olive ￿ brown D a p. green green p.

8.0 34 33 olive + brown E a p. green green p.

8.0 31 31 F a p. green ++ p. green

9.0 33 33 brown F a p. green +++ p.

8.5 30 31 brown F a p. green ++ p.

9.0 32 31 olive brown brown F a p. green ++ p.

a 9.0 33 31 - d. brown olive brown +++ p. brown G

8.5 32 32 - H a p. green olive brown ++ p. green

mean 8.7 31 32

extr 8-9 23-34 28-34

(N=13)

« 9 34 37 23 ++ brown F green p.

Heath habitat

8.0 27.5 28 - brown I a p. green + p.

8.5 29 29 - +++ brown I a p.green* p.

7.5 28 29 - olive brown ++ I a p. green green

7.0 27 28 - I a p. green* ++ green

mean 7.8 28 29

extr 7-8.5 27-29 28-29

(N=4)

8.5 28.5 32 22.5 I S p. green + p. green

* head + pronotum blue-green

Description habitat

A. Klil other - brunneus Hjardemil Hôtel; grassy végétationalong verge (photo4); Oithoptera Chorthippus

B. Klit - C. C. Hjardemil Hôtel; grassy végétation along verge (other locality than A); otherOithoptera brunneus, bigullulus

C. Callunetum& Corex Frestmp; verge of road near Cariciarenariae-Empetretum, Ericetum (photo 2); végétation cov. 100%, 30 cm high: arena-

Festuca ria,Ammophila, rubra, Armeria maritima;other Oithoptera - C. brunneus, C. bigullulus

D. near Klit of road Callunetum & Ericetum cov. 100%, 30 cm Hjardemil Hôtel; verge near Cariciarenariae-Empetetrum, (photo 2); végétation

high; Carei: arenaria, Ammophila,Festuca rubra, Armeria maruima; other Orthoptcra - C. brunneus, C. biguttulus. Omocestus viridulus

E. Frpstrup, near HjardemilKlit Hôtel; végétation cover 100%; verge along field (,Ammophila,Elytrigia repens, Galium verum, Campanula);

other Oithoptera - C. brunneus, C. biguttulus. O. viridulus

F. Bcach; Dunes Hjardemil along the Noith Sea beach: Elymo-Ammophiletumwith Rosa pimpinelliffolia,Galium verum, Pimpinellasaxifraga,

Lathyrusjaponica; other Orthoptcra - C. brunneus, C. biguttulus. C. albomarginatus, O. viridulus

G. Hanslholm Reserve; dunes along the North Sea beach: Elymo-Ammophilelumwith Rosa pimpinelliffolia,Galium verum, Pimpinella saxifraga.

Lathyrus japonica; other Orthoptcra - C. brunneus, C. biguttulus, C. albomarginalus, 0. viridulus

H. Hjardemil Klit Camping; veige of field with Calluna vulgaris, Carex arenaria, Ammophila, Festuca rubra, Holcus lanatus; other Oithoptera -

C. brunneus, C. biguttulus

Viola L Hanstholm Reserve; Carici arenariae-Empetretum(+ Ammophilaarenaria, Corynephorus canescens,Polypodium vulgaris, canina,

Hieracium umbellatum,Uchenes) (photo 3); other Orthoptcra - C. brunneus, C. biguttulus. Myrmeleotettixmaculatus

J- Frostrup; Carici arenariae-Empetrelum,Callunetum,Ericetum, with a.o.Vaccinium uliginosum (photo 2)

24 Nieuwsbrief Saltabel8 (1992)