Nico W. Elfferich Rotterdamse Natuurhistorische Club Is the larval and imaginal signalling of Lycaenidae and other Lepidoptera 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 butterflies 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 butterfly 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 Polyommatini, 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 91 DEINSEA 4, 1998 of the Riodinidae, 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 insects 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 Europe. 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 92 ELFFERICH: vibrating lycaenids 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) Satyrium 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 Zizeeria knysna (Tr) the insect 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 moths 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.