Mating System, Mate Choice and Ultrasonic Calling in a Zaprochiline Katydid (Orthoptera: Tettigoniidae)

Abstract

We describe sexual communication and the mating system of an undescribed genus of zaprochiline katydid. Males produce an ultrasonic calling song described as a series of simple pulses at a carrier frequency near 50 kHz. Zaprochilines contrast with most other katydids in having a narrow diet consisting of pollen. Males in nature exhibited a resource-defence mating system by calling in choruses near flowers which were attractive to females. We determined whether females discriminated among calling males as mates. An early-season sample of male calls showed a correlation between song frequency and both body size and the size of the glands that produce a large, nutritious spermatophore which is eaten by the female. The prediction that larger males would have a mating advantage over small individuals was supported in laboratory experiments. However, examination of paired males in nature failed to reveal any evidence of such a mating advantage. Furthermore, in other laboratory experiments it was found that females preferred high frequency call models, representative of small males, over low frequency calls. It is suggested that females do not prefer calls of large males because only in the early part of the season does male song give information on the size of the male and his spermatophore glands. In addition, spermatophore nutrients may be less important to the nutrition of female zaprochiline than other katydiyds, due to the high-protein pollen diet of this species. Since higher frequencies of calls show relatively greater attenuation with distance, the high frequency calls preferred by females may be perceived as males calling closeby.