An Audiospectrographic Study of Stridulation as an Isolating Mechanism in the Genus Berosus (Coleoptera: Hydrophilidae)12

Abstract

Stress chirps of 12 species of Berosus studied in the laboratory have broad frequency ranges, and most species utilize a major part of the stridulatory file for a given stress chirp. Species occurring together have comparatively different chirps, but those of allopatric species are not always easy to distinguish. Premating sounds, or tremolos, of 4 of the species show greater interspecific differences than the stress chirps and differ from the chirps in several respects, notably timing. Premating sounds are clearly associated with courtship, as can be seen from the fact that sound usually precedes, but does not continue during or after successful mating and egg laying. The premating tremolos of Berosus spp. seem to be an important isolating mechanism. Study of the 30 or more families of beetles which produce sounds may show a similar correlation between acoustic and reproductive behavior.