Crepitation in Schistocerca americana (Orthoptera: Acrididae)

Abstract

Schistocerca americana males were found to crepitate during interactions with other males in the field. More research will need to be Otte (1970) compiled observations on the mating behavior of approximately 100 species of grasshoppers. The mating behavior of Schistocerca lineata (Scudder) is the only member of its genus treated. Loher (1959) studied courtship and aggres- sion in Schistocerca gregaria (Forskal). Neither author mentions crepitation (production of special, non-incidental, wing snap- ping sounds during flight). To our knowledge, then, this is the first report of crepitation in this genus and the social setting in which it was observed. Observations in the field were conducted from April to August of 1992. Crepitations of Schistocerca americana (Drury) were recorded on a Uher 4200 Report Stereo IC tape recorder, and sound recordings were analyzed with a Kay Elemetrics Corporation model 5500 audiospectrograph. For an audiospectrogram of one male's crepitation see Fig. 1. All captured animals that crepitated were males. Such crepitations were observed on eight occasions (out of 18 obser- vation periods) and were seen when two males came into contact with each other during the months of April through July of 1992. A typical observation consisted of a male flying towards a stationary male. At some point the stationary male would fly up and crepitate, in what appeared to be a reaction to the ap- proaching male. After the former male flew away, the station- ary male would usually return silently to the area in which he was previously resting. No crepitations were seen after this time (unless another male approached). A similar situation of males aggressively reacting to one another occurs with Schistocerca gregaria, but only when these animals are stationary on the ground. Then stridulation is observed, but not crepitation. Loher (1959) noted that males of this species used sound in conjunction with mating only when approached by other males. Otte (1992) noticed that both male and female Circotettix rabula (Rehn and Hebard) crepitated in reaction to each other. Before this time, C. rabula males were observed to respond only to the crepitations of other males (Otte 1970). Recently, crepitations were heard on two occasions in which a male and female were interacting with each other, with one interaction ending in a mating. Otte (1992) concluded that these crepitations and interactions were designed to bring the sexes together, and once in close proximity the sexes could still accept or reject one another.