Sound vs. light: wing-based communication in Carboniferous insects.

Acoustic communication is well-known in insects since the Mesozoic, but earlier evidence of this behavior is rare. Titanoptera, an 'orthopteroid' Permian-Triassic order, is one of the few candidates for Paleozoic intersex calling interactions: some specimens had highly specialized broadened zones on the forewings, which are currently considered-despite inconclusive evidence-as 'resonators' of a stridulatory apparatus. Here we argue that the stridulatory apparatus hypothesis is unlikely because the Titanoptera lack a stridulatory file on their bodies, legs or wings.