Complex Vibratory Signalling and Putative Receptor Mechanisms in the Masked Birch Caterpillar, Drepana Arcuata (Lepidoptera, Drepanidae)

The masked birch caterpillar, Drepana arcuata, uses 3 distinct signals when defending its territory from conspecific intruders. The 3 signals are anal scrape, mandible drum and mandible scrape. This study's goals were twofold: first, to test hypotheses on the functional significance of these complex signals, and second, to identify putative vibration receptors in the proleg. Based on experimental trials of size asymmetry certain signal characteristics of the mandible drum and anal scrape were observed to vary between individuals of different mass suggesting the 3 signals could be a result of content based selection and that size information is conferred during an interaction. Trials where the measuring distance was varied, only 2 characteristics of the anal scrape differed significantly between the four recording distances. A dissection study of the proleg discovered that both internal and external structures were innervated. Innervated setae and putative chordotonal organs may function as a multi-component receptor.