Hammering homoplasy: multiple gains and losses of vibrational sounding in cryptine wasps (Insecta: Hymenoptera: Ichneumonidae)

Many hosts of parasitic wasps are, when attacked, either at an immobile stage, living in a concealed environment, or both, thus making their detection especially difficult. Cryptine ichneumonid wasps often parasitize beetle or moth larvae, prepupae or even pupae in tunnels in wood, and many others attack cocooned hosts in various states of concealment. The structure of the antennal tips shows a range of adaptations at least the most extreme of which appear to be involved in locating deeply concealed hosts through vibrational sounding (= echolocation through solid media). We show that, within the Cryptinae, the tips of the antenna are modified into a hammer-like structure that is suitable for knocking a substrate; this form of echo-location is typical to the tribe Cryptini, although it is also found in a few phygadeuontines and in the hemigastrine genus Echthrus. Electron micrographs are presented to illustrate the different degrees of antennal modifications found in the subfamily. Comparative analysis using independent contrasts was then used to demonstrate a statistically significant association between degree of antennal hammer development and attacking, typically wood-boring, beetle hosts of the families Cerambycidae and Buprestidae. (C) 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 96, 82-102.