See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/268810533 Trail following as a rare phenomenon among non-social lappet moth larvae (Lepidoptera: Lasiocampidae) Article in Entomologia Generalis · September 2000 CITATION READS 1 54 2 authors, including: Konrad Fiedler University of Vienna 303 PUBLICATIONS 8,667 CITATIONS SEE PROFILE Some of the authors of this publication are also working on these related projects: Tropical Research Station La Gamba, Costa Rica View project Herbivore communities in the Andean mountain forest zone – comparisons within selected plant species along contrasting environmental dimensions View project All content following this page was uploaded by Konrad Fiedler on 27 November 2014. The user has requested enhancement of the downloaded file. Entomol Gener 11 25(1): 017-025 11 Stuttgart 2000-09 ISSN: 0171-8177 EGT-Nr 1.013 11 Trail Following as a Rare Phenomenon among Non-social Lappet moth Larvae (Lepidoptera: Lasiocampidae) CLAUDIA RUF & KONRAD FIEDLER Received: 1999-10-06/2000-05-15 Accepted: 2000-05-19 RUF C & FJEDLER K [LS Tierokol I, Univ Bayreuth, D-95440 Bayreuth]: Trail Following as a Rare Phenomenon among Non-social Lappet moth Larvae (Lepidoptera: Lasiocampidae).­ Entomol Gener 25(1): 017-025; Stuttgart 2000-10. [Article] Within the Lasiocampidae sociality among caterpillars occurs quite frequently. FITZGERALD & COSTA [1986] suggested that sociality might originate in the ability of solitary ancestral species to mark and follow trails whereas other authors emphasize adaptations to adult morphological constraints as most important selective factors. In this laboratory study we tested whether solitary caterpillars of seven species of Lasiocampidae are able to mark their pathways and follow these trails during a second encounter (solitary trail following). Only caterpillars of Dendrolimus pini (Linnaeus 1758) proved to be able to recognize previously marked trails again. In D pini trails are . marked by dragging the tip of the sternum of the last abdominal segment along the substrate. No silk is used for additional marking in contrast to reports from other non-social larvae in Lepido­ ptera which exhibit trail following behaviour. This study suggests that solitary trail following is of minor importance for the evolution of sociality in the Lasiocampidae. Key words: Dendrolimus pini (Linnaeus 1758) - pine tree lappet - sociality in caterpillars - solitary trail following - trail marking RUF C & FJEDLER K [LS Tierokol I, Univ Bayreuth, D-95440 Bayreuth]: Spurfolge-VerhaJten als seltenes Phlinomen bei nicht-sozialen Gluckenraupen (Lepidoptera: Lasiocampidae).- Ento­ mol Gener 25(1): 017-025; Stuttgart 2000-10. [Abhandlung] Innerhalb der Lasiocampidae tritt Sozialitat bei Raupen relativ haufig auf. FITZGERALD & COSTA [1986] nahmen an, daB der Ursprung der Sozialitat in der Fahigkeit solitarer Vorlauferarten liegen konnte, Spuren legen und folgen zu konnen. Andere Autoren dagegen halten morpholo­ gisch bedingte Zwange der adulten Tiere fur die wichtigsten Selektionsfaktoren. In dieser Labor­ studie wurde getestet, ob solitare Raupen von sieben Gluckenarten flihig sind, ihre Wege zu markieren und beim erneuten Antreffen wiederzuerkennen (soliUi.res Spurfolge-Verhalten). Nur Raupen des Kiefernspinners Dendrolimus pini (Linnaeus 1758) erwiesen sich als fahig, zuvor markierte Wege wiederzuerkennen. Die Bespurung eines Weges erfolgt bei D pini dadurch, daB die Spitze des Sternum des letzten Abdominalsegments ab er das Substrat gezogen wird. Dabei wird zur zusatzlichen Markierung keine Seide verwendet, wie dies von anderen nicht-sozialen Schmetterlingsraupen berichtet wird, die solitares Spurfolge-Verhalten zeigen. Die Ergebnisse dieser Studie legen nahe, daB solitares Spurfolge-Verhalten fOr die Entwicklung der Sozialitat bei den Lasiocampidae von geringer Bedeutung ist. Schlilsselbegriffe: Dendrolimus pini (Linnaeus 1758) - Kiefernspinner - SozialiUi.t bei Raupen - solitares Spurfolge-Verhalten - Spurenlegen 0171-8177/00/0025-0017 ,$ 2.25 © 2000 E. Schweizerbart'sche Verlagsbuchhandlung, D-70176 Stuttgart 018 CLAUDIA RUF & KONRAD FIEDLER 1 Introduction Most of the 160,000 described species of .Lepidoptera have solitary larvae since eggs are laid singly or caterpillars disperse as soon as they hatch from egg clusters. There are only about 300 species identified so far with social caterpillars which live together in large communities sometimes exceeding hundreds of caterpillars [COSTA & PIERCE 1997]. Although this list is certainly incomplete, sociality in caterpillars is a rare phenomenon. However, sociality is taxonomically widespread in the Lepidoptera, occur­ ring in 20 or more families, and therefore has likeJy evolved numerou s times in parallel. As solitary life-styles are ancestral in the Lepidoptera [POWELL et al 1999: data on basal Lepidoptera], sociality must have evolved in response to selective pressures enhancing fecundity of females or survival of group living caterpillars. 2 hypotheses are discussed: (a) Sociality may be derived from the larval behaviour of solitary ancestral species that marked trail systems between resting and feeding sites. Encountering trails of other individuals while extending their own trails might have served as initial stimulus to aggregate if survival of these larvae in chance groupings was enhanced (e.g. by thermo­ regulation, or group defense). Evolution might have subsequently favoured females that laid their eggs in groups or clusters [FITZGERALD & COSTA 1986]. Under this hypothe­ sis, evolution of larval societies was primarily spurred through selection on larval char­ acters, and communicative abilities of caterpillars provide a central precondition. (b) Alternatively, energetic constraints effective in adult moths (e.g. high wing load, inability to replenish nutrient reserves through adult food incom e) may have pro­ moted the evolution of egg clustering, which is especially advantageoll s for species that totally rely on larval resources because adults do not feed [HEBERT 1983]. Egg clustering may further increase female fecundity [COURTNEV 1984]. If staying together had selective advantages for the offspring social trail following might have evolved as a consequence of the necessity to insure cohesion of group members. Communication by trail following would therefore have evolved secondarily, whereas the initial precondition of larval gre­ gariousness (i.e egg clustering) would have been shaped by selection on adu It moths. In the Lasiocampidae, sociality in caterpillars is particularly widespread and occurs in different subfamilies. Representatives of at least 17 unrelated genera are known to live in groups [AURIVILLIUS 1927, AHERKAR et al 1997, COSTA & PIERCE 1997, PARK & BVUN 1997, BOGNER 1999] and many further cases are to be expected as the highest lasiocampid diversity occurs in the tropics, where most of the larvae are unkn own yet. If solitary trail following were ancestral and evolved before sociality one would predict this feature to be widespread within the Lasiocampidae. The aim of the present study was to test whether there are any solitary species showing trail foHowing behaviour in a range of Old World genera. Trail marking behaviour as a means of facilitating the relocation of suitable resting places or profitable feeding sites could be expected especially in' species which rest at trunks or large branches and feed high up in the canopy of larger trees. 2 Materials and Methods For our studies we used the following species (origin in parentheses): Gastropacha populi­ folia (Denis & SchiffermUller 1775) (Gmunden at the Traunsee, Austria), Dendrolimus pini (Lin­ naeus 1758) (Nicklheim, Bavaria), Bufoidia pittawayi (Wiltshire & Legrain 1997) (Republic of Yemen), Cosmotriche lobulina (Denis & SchiffermUller 1775) (Nicklheim, Bavaria), Lasiocampa quercus (Linnaeus 1758) (B ayreuth, Bavaria), Lasiocampa tri/olii (Denis & Schiffermtiller 1775) (Oberlausitz, Saxonia) and Macrothylacia rubi (Lillllaeus 1758) (Bayreuth, Bavaria). Caterpillars were provided by breeders or obtained from th offspring of females collected in the wild. Trail Following in Non-social Lappet moth Larvae 019 Experimental design was based on the assumption that a caterpillar must be able to recognize its own trail again after having passed (and potentially marked) its path only once. For this pur­ pose we used aY-test bioassay constructed with small wooden rods (4mm in diameter, 5cm long). To prevent the caterpillars from leaving the maze, rods were lifted about 2cm above the ground by two small pieces of wood each. There was no wooden support directly underneath the point of contact of the three rods to exclude the possibility that any silk or pheromone left by a preceding caterpillar would influence the decision of a subsequent caterpillar passing the maze (Fig 1). alternative pathways Stem section " point of decision 1cm Fig 1: Experimental design for the Y -test bioassays. Rods were lifted above the substrate to pre­ vent the caterpillars from leaving the maze. There was no wooden support underneath the point of contact of the rods. Caterpillars were individually placed with the help of a pair of forceps on the stem of the Y and were allowed to crawl to the ramification were only one arm of the Y was attached at this time. After having passed the arm the caterpillar was removed from the end of the rod by offering a small twig to crawl on and was then again allowed to crawl onto the stem. This time a second