Sound production and cannibalism in larvae of the pine-sawyer beetle Monochamus sutor L.(Coleoptera: Cerambycidae)

One-year old larvae of the pine-sawyer beetle, Monochamus sutor L. (Coleoptera: Ceram­ bycidae), produced regular, chirping sounds, easily heard up to 10 meters away. Larvae were positioned within their hibernation tunnel in sapwood of recently fire-killed spruce and pine trees. Their heads were directed outwards, and the sound was probably produced by the scratching of their mandibles against the bark. Since the larvae produce this sound in spite of the risk of attracting parasites and predators such as wood-peckers, this behaviour most likely has an adaptive value. We suggest that sound production helps a larva to secure resources around its hibernation tunnel for its own development by keeping away other potentially competitive larvae. That the larvae are cannibalistic was demonstrated during a trial perfor­ med in petri dishes filled with sawdust. Any larva ignoring the sound signal could therefore face a real threat of being killed.