Exploitation of sexual signals by predators and parasitoids

Signals used to attract mates are often conspicuous to predators and parasi tes, and their evolution via sexual selection is expected to be opposed bg viability selection. Many secondary sexual trails may represent a compromis e between attractiveness and avoidance of detection. Although such signal e xploitation appears to be widespread, most examples come from species that use acoustic or olfactory mating signals, and relatively few cases of visua l signal exploitation can be substantiated. Because males are usually the s ignaling sex, they are more at risk from predators or parasitoids that loca te prey or hosts by sexual signals; this differential selection on the two sexes can affect the intensity of sexual selection on male ornamental trait s. The notable exception to mab signaling and female attraction occurs in p heromone-producing insects, particularly lepidopterans, which show an oppos ite pattern of female odor production. Exploitation of such sex pheromones is relatively rare We discuss reasons for the reversal in sex roles in thes e species and its implications for signal exploitation. Changes in signals that appear to be adaptations to avoid predation include the use of differe nt signal modalities, changes in signaling behavior, loss of signals, and a lteration of signal characteristics such as Pitch. Selection pressure from signal exploiters could lend to the production of a novel signal and thus f acilitate speciation. Relatively little work has been done an adaptations o n the part of the exploiting species, but such adaptations could indirectly influence the mating system of the predator or parasitoid. Signal exploita tion is also expected to be a fruitful source of examples of coevolution. F inally, plants emit attractants analogous to secondary sex characters in an imals, and may also be vulnerable to signal exploitation.