Trail following as a rare phenomenon among non-social lappet moth larvae (Lepidoptera : Lasiocampidae)

Within the Lasiocampidae sociality among caterpillars occurs quite frequent ly. FITZGERALD & COSTA [1986] suggested that sociality might originate in t he ability of solitary ancestral species to mark and follow trails whereas other authors emphasize adaptations to adult morphological constraints as m ost important selective factors. In this laboratory study we tested whether solitary caterpillars of seven species of Lasiocampidae are able to mark t heir pathways and follow these trails during a second encounter (solitary t rail following). Only caterpillars of Dendrolimus pini (Linnaeus 1758) prov ed 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 segmen t along the substrate. No silk is used for additional marking in contrast t o reports from other non-social larvae in Lepidoptera which exhibit trail f ollowing behaviour. This study suggests that solitary trail following is of minor importance for the evolution of sociality in the Lasiocampidae.