Nico W. Elfferich Rotterdamse Natuurhistorische Club

Is the larval and imaginal signalling of and other related to communication with ants?

Ellferich, N.W, 1998 - Is the larval and imaginal vibration signalling of Lycaenidae and other Lepidoptera related to communication with ants? - DEINSEA 4: 91 - 95 [ISSN 0923-9308]. Published 30 August 1998

The larval instars, pupae and adults of ant-associated lycaenid have to integrate into the ants' communication system in order to appease the normal aggressive behaviour of the ants and hence to profit from protection from predators. The vibration signalling of caterpillars, pupae and adults (imagines) was studied and its impact on the appeasement of ant aggressiveness after the emergence of the from the pupal skin was tested. As the vibration signalling in the larval instars and the emerging butterfly is only found in lycaenid species, which are at the same time the species with ant-attendant relationships in their life-cycle, the vibration might play a role as manner of communication. During emergence, the communi- cation only works well in the , while other lycaenids evoke aggressive behaviour in the ants and get killed easily. In case of adults a pheromonal substance might also be involved.

Speelt het larvale en imaginale vibratie signaal van Lycaenidae en andere vlinders een rol bij de commu - nicatie met miere n ? – De larvale tussenstadia, poppen en volwassen exemplaren van met mieren geasso- cieerde blauwtjes (vlinders) zijn genoodzaakt zich te integreren in het communicatie systeem van de mie- ren om het normale agressieve gedrag van deze dieren te kalmeren. Het doel is te profiteren van de bescher- ming die mieren bieden tegen predatoren. De vraag is of het vibreren van de blauwtjes daarin een rol speelt. Daartoe werd het vibratie signaal van rupsen, poppen en imago’s van verscheidene vlindersoorten bestu- deerd en werd bekeken in hoeverre het signaal de agressiviteit van mieren deed afnemen nadat de vlinders uit de pophuid gekropen waren. Aangezien het afgeven van een vibratie signaal door de larvale tussensta- dia en de uitkomende vlinder uitsluitend bij Lycaenidae-soorten (die tijdens hun levenscyclus regelmatig door mieren bezocht worden) werd vastgesteld, wordt geconludeerd dat het vibreren een belangrijke rol kan spelen bij de communicatie tussen vlinder en mieren. Tijdens het uitkomen van de pop bleek de communi- catie uitsluitend goed te werken bij Polyommatini-soorten, terwijl andere Lycaenidae-soorten agressief gedrag bij de mieren ontlokten en direct werden gedood. Sommige vlinders (imago’s) produceren ook een feromoon om de mieren te kalmeren.

Correspondence: N.W. Elfferich, Reviusrondeel 223, NL-2902 EG Capelle a/d IJssel, The Netherlands, phone 31 10 4518428

Keywords: Lycaenidae, caterpillar vibration, pupal vibration, imaginal vibration, ant aggressiveness

I N T R O D U C T I O N For more than 200 years we know that rubbed together by muscular contractions. the pupae of lycaenids produce sounds For more than 40 lycaenid species it has (Kleemann 1774). Prell (1913) detected the been shown that this kind of stridulation is a sound organs in the intersegmental split normal behaviour of pupae (Elfferich 1988, between the 5th and 6th abdominal segment. 1989; Elfferich & Jutzeler 1988). Downey On the 6th segment there is a dentated plate (1966, 1967) tested a number of nearctic and on the 5th segment a vibrating plate is species and Downey & Allyn (1973) analy- present. The plates produce a sound when zed the sound organs by SEM. In his study

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of the , DeVries (1990) discover- Vibration re c o r d i n g ed sound producing organs on caterpillars: The vibration signals of caterpillars, pupae he tested lycaenid caterpillars and found and adults could only be made audible by vibration signals too (DeVries 1991a, b). means of a contact microphone. They were Often larval instars of lycaenid species have simultaneously recorded via a record-player- relationships with ants. These relationships element and by a specially prepared microp- can be quite weak, like in hairstreaks hone (Telefunken TD-20). The were (Theclinae) which do not form stable rela- placed on a piece of sigarette-paper placed tionships with ants. Most lycaenids, for exa- directly on the microphone membrane. In mple the P l e b e j u s and P o l y o m m a t u s s p e - this way, it was also possible to record the cies, are steadily myrmecophilous: most vibrations of very small caterpillars, such as mature larvae live ant-associated (Fiedler Maculinea nausithous. To record the vibra- 1988; Fiedler 1991; Schurian & Fiedler tions after emergence of adults and during 1991). The most intense relationship is the wing expansion, a small light T- s h a p e d found in M a c u l i n e a -species, who spend nine perspex construction was made. This was months of their caterpillar life as parasites placed upside down on the microphone in M y r m i c a nests (Elfferich 1963; T h o m a s membrane. A light piece of a twig was glued & Elmes 1987). As ants live in high num- on the top of the vertical leg under a small bers in organized colonies with highly deve- angle. Most of the just emerged butterflies loped communication systems (Hölldobler moved to the highest place to stretch the & Wilson 1990) and are potential caterpil- wings. To test whether the sound during l a r-predators, the main problem for the eclosion was produced by the pupal sound caterpillars is to integrate into the ant com- o r gan, the pupal skin was removed from the munication system. The close relationship abdomen of some Polyommatus icaru s . T h i s with the ants gives rise to the idea that, next was done 45 to 30 minutes before the expec- to adaptations to prevent predation, some ted emergence. Furthermore, videorecor- kind of communication takes place. It is not dings were made by means of a Watec CCD unlikely that the vibration of caterpillars, c o l o u r-camera (Wat-202) and a JVC S-VHS pupae and possibly adult butterflies is a way v i d e o r e c o r d e r. to communicate with ants. Testing the reaction of ants on eclosing In this study, many caterpillars, pupae and a d u l t s imagines were tested for vibrational signal- Some tests were run to observe the beha- ling. Furthermore, the importance of vibra- viour of the ants towards newly hatched but- tions of adults directly after emergence from terflies. These tests were done in plastic the pupal skin in the presence of ants was boxes connected with plasternests where the s t u d i e d . ant colonies were kept. These boxes were normally in use as a feeding place for the ant MATERIAL AND METHODS c o l o n y. A few days before emergence the Collection of test species pupae were placed into the plastic box. T h e Most of the caterpillars, pupae and butter- behaviour of the emerging butterfly and the flies used for the experiments have been ants were recorded with a JVC GR-77 video- bred from eggs laid by females in captivity. c a m c o r d e r. Most females were captured in T h e Netherlands or other countries in We s t e r n R E S U LT S . The eggs of Polyommatus icaru s Caterpi llar vibr ations were collected in Crete, Greece. Some eggs All tested lycaenid caterpillars regardless of were kindly given by other entomologists. their taxonomic group, always produced a

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Table 1 Caterpillars tested for vibration (this study). t e r f l y ’s abdomen was already separated from the pupa. Some more tests were run with fully no vibration vibration developed pupae of Polyommatus icaru s t h a t were treated in such a way that the pupal skin Pieris napi (L) Lycaena helle (D&S) Melanargia galathea (L) Lycaena phlaeas (L) with the sound organs was separated from the Epirrita dilutata (D&S) Heodes tityrus (Poda) abdomen just before eclosion. The newly Gymnoscelis rufifasciata (Haw)* Quercusia quercus (L) e m e rged butterflies also showed vibrations. Mimas tiliae (L) ilicis (Esp) During the emergence of the butterflies, vibra- Adscita statices (L) Satyrium w-album (Esp) Zygaena lonicerae (Schev) Callophrys rubi (L) tions were recorded. At the experimental con- Sideridis albicolon (Hüb) Maculinea teleius (Bergstr) struction it was possible to record vibrations Maculinea nausithous (Bergstr) after the emergence during the period when knysna (Tr) the showed hestitating movements to Celastrina argiolus (L) Philotes baton (Bergstr) find a place for expanding the wings. A f t e r Plebejus argus (L) that, the imago stopped giving vibration sig- Vacciniina optilete (Knoch) nals. However, after the expansion of the Lysandra coridon (Poda) wings, a slight vibration signal was recorded Polyommatus icarus (Poda) at the moment the imago squeezes its wings t o g e t h e r. Tests with other freshly emerged but- terflies of other groups and gave com- *The caterpillars of Gymnoscelis rufifasciata reacted by drumming with their legs, resulting in a vibration-like signal parable results (Table 3). Once being able to f l y, no vibrations were detected in any tested butterfly species. humming vibration. However, no vibration was recorded with caterpillars of other Lepidoptera (Table 1). There was no detecta- B u t t e r f ly vibration and ant behav i o u r ble difference between the vibrations produ- Polyommatus icaru s (Rott) and P l e b e j u s ced by myrmecophilous and non-myrmecop- a rg u s (L) were not attacked during the emer- hilous species. Furthermore, in the audio- as gence of the butterflies from the pupal skin in well as in the video-recordings no changes in the nest of Lasius niger (L), but Lycaena phla - vibration as a reaction to visiting ants could be e a s (L) and Satyrium ilicis (Esp) were killed. found. After physical contact with ants there In a nest with Myrmica ru g i n o d i s (Nyl) all were no reactions either. The vibrations were four butterfly species were killed. Imagines of also produced by the Maculinea nausithous Polyommatus icaru s (Rott), Plebejus arg u s and M. teleius larvae in the adoption stage. (L) and Zizeeria knysna ( Tr) could escape wit- During the pupation, vibrations are produced hout any harm from the colonies of L a s i u s too. A sound producing organ was searched n i g e r (L). After the butterfly had left the pupal for in the caterpillars but could not be found. skin, the ants follow the footmark of the ‘pro- Only in the pupal instar, when the sound t e c t e d ’ b u t t e r f l y. On spots where the imago o rgans are developed, the vibrations result in a stopped for a moment during the search for a stridulation signal that is audible. good spot for wing-expansion, after a few seconds some ants gathered. During the B u t t e r f ly vibrations during and after emer- expansion and ‘drying’ of the wings the ants gence from the pupal skin crawled freely over the butterfly. After about During eclosion, all lycaenid butterflies gave one hour, as the imago is ready to fly, the ants strong vibrational signals whereas the non- started to show aggressive behaviour, but then lycaenid species never produced vibrations the butterfly could easily escape by flying ( Table 2). This was remarkable because a w a y. sounds were recorded at the moment the but-

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Table 2 Imagines of butterflies tested for vibrations during ty of vibrations in relation to the intensity of the emergence from the pupal skin (this study). m y r m e c o p h i l y. The vibrations can best be seen as a method of general communication vibration no vibration between lycaenids and ants, rather than ena- Lycaena helle (D&S) Hamaeris lucina (L) bling species-specific communication. T h e Lycaena phlaeas (L) Pieris brassicae (L) fact that M a c u l i n e a species are not able to Heodes tityrus (Poda) Leptidea sinapis (L) establish a fine tuned communication by vib- Heodes ottomanus (Lef) Pieris rapae (L) Quercusia quercus (L) Vanessa atalanta (L) rations with their specific host ants (De Vr i e s Thecla betulae (L) Inachis io (L) et al. 1993), also appears to apply to all lyca- Satyrium ilicis (Esp) Araschnia levana (L) enid caterpillars. During the emergence from Callophrys rubi (L) Melitaea didyma (Esp) the pupal skin, again, only the lycaenid spe- Lampides boeticus (L) Zizeeria knysna (Tr) cies produce vibrations. However, during the Celastrina argiolus (L) last stage of wing expansion, all butterfly Philotes baton (Bergstr) species could give a slight vibration during a Plebejus argus (L) short period (not to be confused with the Vacciniina optilete (Knoch) Aricia agestis (Schiff) warming up vibrations before taking off ) . Lysandra coridon (Poda) Polyommatus icarus (Poda) T he ant -a tt endant life st yl e, al be it i n v a r i o u s intensities, is among the European Table 3 Butterflly species producing slight vibrations after expansion of the wings (this study). Lepidoptera only known from the lycaenids. As the ability to produce vibration signals is Lycaena phlaeas (L) also restricted to lycaenids, (no other tested Maculinea nausithous (Bergstr) butterfly species showed this behaviour), Polyommatus icarus (Rott) Pyrgus malvae (L) signalling by vibrations could well be related Pieris brassicae (L) to communication with ants. The protection Pieris rapae (L) through ‘speaking foreign languages’ is suf- Vanessa atalanta (L) ficient to protect larval and pupal instars Aglais urticae (L) Araschnia levana (L) from attacks by ants. They are obviously Melitaea didyma (Esp) able to appease the natural aggressiveness of Leptidea sinapis (L) the ants. Once being a butterfly, this way of Deilephila elpenor (L) communication cannot guarantee full under- Melanchra persicariae (L) Abrostola triplasia (L) standing anymore. In the presence of certain glyphica (L) ant species, only the Polyommatini survived mi (Clerck) eclosion. Adscita statices (L) Phragmatobia fuliginosa (L) Epione repandaria (Hufn) Critical analysis of the sound-recordings of d i fferent groups of Lycaenidae during the e m e r gence revealed just a small diff e r e n c e between the Polyommatini and the other CONCLUSION AND DISCUSSION groups. Just before t he emerge nce all The caterpillars and pupae of all tested lyca- lycaenids give strong signals but in the enid species are able to produce vibration Polyommatini, in most cases, the vibrations signals, while the caterpillars of all other last somewhat longer, probably because of Rhopalocera and species do not show the slower emergence from the pupal skin. this behaviour. Although it seems to be a During and after eclosion, the influence of normal lycaenid behaviour, no diff e r e n c e communication by vibration to appease the could be found in the frequency and intensi- ants is of minor importance. Based on the

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behaviour observations, it appears more This pheromone is only successful in some likely that some lycaenid butterflies produce ant species, and is only effective for a short a pheromonal substance to calm the ants. p e r i o d .

R E F E R E N C E S D e Vries, P.J. , 1990 - Enhancement of symbiosis between butterfly caterpillars and ants by vibrational E l fferich, N.W., 1988 - Geluidsproductie van communcation - Science 248: 11 0 4 - 11 0 6 Lycaenidae- poppen. Vlinders 3(2): 8-12 D e Vries, P.J., 1991a - Call production by myrmecophi- E l fferich, N.W., 1989 - De merkwaardige vriendschap lous riodinid and lycaenid butterfly caterpillars tussen mieren en blauwtjes - Vlinders 4(3): 12-15 (Lepidoptera): morphological, acoustical, functional E l fferich, N.W., & Jutzeler, D., 1988 - and evolutionary patterns - American Museum Geräuschproduktion bei Ly c a e n i d e n - P u p p e n Novitates 3025: 1-23 (Lepidoptera) - Mitt. Entomologische Gesellschaft D e Vries, P.J. , 1991b - Detecting and recording the calls Basel 38(4): 156-168 produced by caterpillars and ants - Journal of F i e d l e r, K., 1988 - Die Beziehungen von Bläulings- Research on the Lepidoptera 28(4): 258-262 raupen (Lepidoptera, Lycaenidae) zu A m e i s e n D e Vries, P.J., Cocroft, R.B., & Thomas, J.A., 1993 - (Hymenoptera, Formicidae) - Nachr. ent. Ve r. A p o l l o , Comparison of acoustical signals in M a c u l i n e a Frankf. N.F. 9(1): 33-58. butterfly caterpillars and their obligate host M y r m i c a F i e d l e r, K., 1991 - Systematic, evolutionary and ants - Biological Journal of the Linnean Society 49: ecological implications of myrmecophily within the 2 2 9 - 2 3 5 Lycaenidae (Insecta: Lepidoptera: Papilionoidea) - D o w n e y, J.C., 1966 – Sound production in pupae of Bonner Zoologische Monographien 31: 1-134 Lycaenidae - Journal of the Lepidopterists' Society H ö l l d o b l e r, B., & Wilson, E.O, 1990 - The ants - 20(3): 129-155 Harvard University Press, Cambridge D o w n e y, J.C., 1967 – Sound production in Netherlands' Kleemann, C.F.C., 1774 - Beiträge zur Natur- und Lycaenidae - Entomologische Berichten 27: 153-157 Insektengeschichte 4: 123 D o w n e y, J.C., & Allyn, A.C. , 1973 - Butterfly ultra- Prell, H, 1913 - Über zirpende Schmetterlingspuppen - structure. I. sound production and associated abdomi- Biol. Zentralblatt 33: 496-501 nal structures in pupae of Lycaenidae and Riodinidae- Schurian, K.G., & Fiedler, K., 1991 - Einfache Bulletin of the Allynmuseum 14 Methoden zur Schallwahrnehmung bei E l fferich, N.W., 1963 - Kweekervaringen met Bläulingslarven (Lepidoptera: Lycaenidae) - Maculinea alcon. Entomologische Berichten 23: 46- Entomol. Zeitschrift 101(21): 393-412 52 (translated in German by D. Jutzeler: Thomas, J.A., & Elmes, G.W., 1987 - Die Gattung Zuchterfahrungen mit Maculinea alcon. Mitt. M a c u l i n e a - in: - Tagfalter und ihre Lebensräume - Entomologische Gesellschaft Basel 38: 134- Schweizerischer Bund für Naturschutz, Basel 1 5 0

Received 20 August 1997 Accepted 16 September 1997

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DEINSEA - ANNUAL OF THE NATURAL HISTORY MUSEUM ROTTERDAM P. O . B o x 2 3 4 5 2 , N L - 3 0 0 1 K L R o t t e r d a m T h e N e t h e r l a n d s

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