Invitation by vibration: recruitment to feeding shelters in social caterpillars
Sociality is widespread in caterpillars, but the communication mechanisms used for group formation and cohesion are poorly understood. Here, we present the first evidence that caterpillars produce complex vibratory signals to advertise food and shelter sites to conspecifics. We first tested the hypothesis that early instars of the masked birch caterpillar (Drepana arcuata) actively form groups. Larvae placed alone on different leaves of a birch twig began assembling within minutes and forming groups of 2–6 at a median time of 2 h. In Y-choice experiments, larvae joined arms occupied by conspecifics significantly more frequently than unoccupied arms. To test the hypothesis that group formation is vibration-mediated, signals were monitored in solitary residents of silk leaf shelters before and during natural recruitment events. Four distinct signal types were recorded: anal scraping, mandible drumming, mandible scraping, and buzz scraping. Anal scraping and buzz scraping were the most common in residents prior to being approached, and these signals were strongly correlated to feeding and laying silk. Signaling occurred in 100% of residents, and higher signal rates resulted in significantly faster recruitment times. As a recruit approached a resident, complex signaling interactions occurred, which may communicate information about resource quality or location. We conclude that caterpillars, similar to other social animals, use acoustic communication to advertise resources. The vibratory signaling repertoire of these tiny caterpillars exhibits a complexity rivaling that of eusocial insects. Further investigations of vibroacoustic communication are essential to fully appreciate the intricacies of social interactions in caterpillars and other juvenile insects.
Group living provides many survival benefits to juvenile insects such as caterpillars, but little is known about the communication signals mediating social interactions such as group formation. Our study shows that caterpillars use vibration signals to “invite” conspecifics to social gatherings. Pinhead-sized early-instar caterpillars (Drepana arcuata) are capable of locating conspecifics on birch leaves to form small groups. But how do they accomplish this? We report that individual resident caterpillars established in a silk shelter produced complex vibrations by dragging their anal segments, scraping and drumming their mouthparts, and tremulating their bodies to advertise a feeding spot and shelter. These results provide the first evidence that caterpillars use vibratory signaling to form social groups, providing insight into the poorly understood role of vibratory communication in juvenile insects.
KeywordsGroup living Communication Vibration Recruitment Larvae Sociality
We are grateful to Jake Miall for help with insect collection. This research was funded by the Natural Science and Engineering Council of Canada (2014-05947), the Canadian Foundation for Innovation (9555) and an Early Researcher Award (ERO7-04-1-44) to JEY, and the Brazilian National Council of Scientific and Technological Development of Brazil (301847/2015-0) to RNG.
- Blumstein DT, Daniel JC, Evans CS (2010) JWatcher V1.0. University of California, Los Angeles and Macquarie University, SydneyGoogle Scholar
- Bradbury JW, Vehrencamp SL (2011) Principles of animal communication, 2nd edn. Sinauer Associates, SunderlandGoogle Scholar
- Bryner R (1999) Drepanidae - Drépanidés. In Les Papillons et leur Biotopes: Espèces; Danger qui les menacent; Protection. Suisse et regions limitrophe, vol. 2 (ed. L. S. p. l. P. d. l. Nature), pp. 447–476 Switzerland: Pro NaturaGoogle Scholar
- Cocroft RB, Hamel JA (2010) Vibrational communication in the “other insect societies”: a diversity of ecology signals, and signal functions. In: O’Connell-Rodwell CE (ed) The use of vibrations in communication: properties, mechanism and function across taxa. Transworld Research Network, Kerala, India, pp 47–68Google Scholar
- Costa JT (2006) The other insect societies. The Belknap Press of Harvard University Press, CambridgeGoogle Scholar
- Hill PSM (2008) Vibration communication in animals. Harvard University Press, LondonGoogle Scholar
- Hograefe T (1984) Subtrat-stridulation bei den koloniebildended Blattwespenlarven von Hemichroa crocea (Geoff.) (Hymenoptera:Tenthredinidae). Zool Anz 213:234–241Google Scholar
- Hrncir M, Barth FG (2014) Vibrational communication in stingless bees (Meliponini): the challenge of interpreting the signals. In: Cocroft RB, Gogala M, Hill PSM, Wessel A (eds) Studying vibrational communication. Springer, New York, pp 349–374Google Scholar
- Matheson SM (2011) Vibratory mediated spacing in groups of insect larvae (Drepana arcuata, Lepidoptera; Scolytus multistriatus, Coleoptera). M.Sc. Dissertation, Carleton UniversityGoogle Scholar
- Rose AH, Lindquist OH (1997) Insects of eastern hardwood trees. Canadian Forestry Service, Ottawa, Forestry Technical Report 29Google Scholar
- Warrant EJ, Kelber A, Kristensen NP (2003) Eyes and vision. In: Kristensen NP (ed) Handbook of zoology, Part 36, Lepidoptera, moths and butterflies, vol 2: morphology, physiology and development, vol IV. Walter de Gruyter, Berlin/New York, pp 325–359Google Scholar
- Yack JE (2016) Vibrational signaling. In: Pollack GS, Mason AC, Fay RR, Popper AN (eds) Springer handbook of auditory research: insect hearing. Springer, New York, pp 99–123Google Scholar