Necromone Death Cues and Risk Avoidance by the Cricket Acheta domesticus: Effects of Sex and Duration of Exposure

Abstract

We document that the cricket, Acheta domesticus, avoids “necromone” chemical cues of death associated with treated surfaces and shelters (i.e., ethanol extracts of cricket bodies, oleic acid or linoleic acid). Initially we tested male responses to male body extract, oleic acid, or linoleic acid associated with shelters. Body extract was more repellent than either oleic or linoleic acid at a dose of 10 body equivalents per shelter. At 15 or 20 body equivalents/shelter extract and oleic acid were similarly repellent but linoleic acid was weaker. We next tested responses of males or females to shelters and surfaces treated with body extracts of males, females, a male-female mixture, or oleic acid. Repellency was evaluated at 1, 16, and 22 h following introduction. Body extracts elicited more immediate aversion than did authentic oleic acid (1 h). Females showed declining aversion with time (1, 16, 22 h), especially with regard to male extract. Alternatively, males showed increasing aversion with time, particularly to female extract. Both sexes showed weak responses to oleic acid at 1 h, but significant aversion at 16 and 22 h. We suggest that females may be less risk aversive as they seek out singing males holding established territories (i.e., mobility makes risk transient). Alternatively, males may respond more strongly to female necromone as this would reduce attraction of females to their territory. Finally, we consider a classic paper that documents a strong cricket repellent associated with tissue-covered perches. We provide new evidence that this repellent was likely an unsaturated fatty acid.