Plant Defense Signaling from the Underground Primes Aboveground Defenses to Confer Enhanced Resistance in a Cost-Efficient Manner

Abstract

The cuticular hydrocarbons from adult Phormia regina (Meigen) were characterized by gas chromatography-mass spectrometry. Both sexes had similar components in nearly identical quantities, consisting of complex mixtures of saturated n-, monomethyl- and dimethylalkanes from 23 to 33 total carbons. Although no diet-, age-, or sex-specific differences were observed, cuticular hydrocarbons were shown to be involved in copulatory behavior. Hydrocarbon profiles of wild, compared to laboratory reared flies, showed no major differences. Behaviorally, males responded the same to dead decoys of either sex. Removal of the hydrocarbons, using hexane, from either male or female decoys, did not affect the number of mating strikes, but markedly reduced the number of copulatory attempts and the amount of time males spent mounted on either decoy. House fly, Musca domestica L., males when paired with a female M. domestica decoy produced copulatory attempts: whereas, when P. regina males were placed with M. domestica female decoys, there were no copulatory attempts. It is concluded that the cuticular hydrocarbons of P. regina function as species-specific but not sex-specific mating cues and elicit species-specific copulatory behavior in males.