Sound Production and Its Evolutionary Significance in the Blattaria

Abstract

Cockroaches produce sounds by rubbing the abdomen against the wings, tapping the substrate, striking the wings against the abdomen, expelling air through the spiracles, and scraping the pronotum over the costal veins (stridulation). Some of these sounds are made by both sexes when the insects are “disturbed” or by males when they court. Two methods of sound production, namely, stridulation and expulsion of air through the second abdominal spiracles, have evolved in the Oxyhaloinae. Stridulating structures have been found in several genera of the ovoviviparous Oxyhaloinae (Nauphoeta, Leucophaea, Henschoudetenia, Oxyhaloa, Jagrehnia) and 1 genus of Panchlorinae (Panchlora) of the Blaberidae. The hypothesis is presented that stridulating structures in the Oxyhaloinae first evolved, in both sexes, on those parts of the pronotum and tegmina that were rubbed together during struggling movements made when the insects were seized by a predator; originally the sound produced, after stridulating structures evolved, may have had a defensive function. Stridulation by males during courtship has so far been observed only in Nauphoeta cinerea (Olivier). Various behavior patterns of males of different blaberids suggest that vibratory and pumping movements, possibly employed to disseminate a pheromone, led to the production of rhythmical sounds in N. cinerea which may have sexual meaning to the female.