The Tettigoniidae: Biology, Systematics and Evolution

by fireflies on calling heterospeciflcs (Lloyd 1984) or the location of calling crickets by tachiniid flies (Cade 197 5). Sexual selection theory would predict that if there were any risks involved in mating then the sex offering the highest investment should take fewer of them. Given these factors and an inherent risk of detection by predators of calling individuals, males are more likely to signal than females (Thornhi111979). Further, if the quantity (length and/ or loudness) of the acoustic signal were correlated with the risks of exposure, we may predict that insects calling from exposed perches, or in areas of high predation, would use calls with a low duty cycle (the calls are short and widely spaced in time). Belwood provides an extensive account of defensive strategies used . by tettigoniids in the tropical rainforests of Central and South America. Her discussion includes both cryptic strategies in avoiding day­ time predators and also signalling strategies avoiding those operating at night As the signal shortens so selection is transferred from the caller to the searching female, and male location may become more risky than calling itself. At this juncture it may be advantageous for the female to call in reply to the male. This role reversal in signalling often results in duetting where the male calls and the female replies within a very narrow time window. The male now searches for the female, taking on both risks of calling and moving.