Macroptery Might Produce More Attractive Calling Songs: Acoustic Differences between Two Wing Morphologies of Metrioptera bicolor Philippi (Orthoptera: Tettigoniidae)

Abstract

Wing dimorphism is a widespread phenomenon of many insect species. The katydid species Metrioptera bicolor Philippi displays distinct wing dimorphism. In this paper, we recorded the calling songs of two wing morphologies of the species and observed the acoustic generators under stereoscope and scanning electron microscope (SEM). The two wing morphologies showed differences in acoustic signals but no obvious differences in morphological traits. The individuals with long hind-wings produced an energetic call, i.e., the calling songs with longer pulse duration but shorter interval. Therefore we infer that the advantage of acoustic signals is a compensation for the weakness in reproduction. Furthermore, some molecular tests were performed to clarify the differences between them at a molecular level. The individuals with long hind-wings got together, while the short-winged individuals were in a group. We proposed that the molecular difference has already existed between these two groups at birth. From the consistency of the stridulatory organs and the differentiation of the acoustic signals, we could infer the behavioral traits might evolve rapidly than the morphological features.