Courtship behavior and discrimination between potential mates by male Delia antiqua (Diptera: Anthomyiidae)

The repertoire of courtship behaviors of male onion maggots, Delia antiqua (Meigen), in a laboratory bioassay chamber, was analyzed by direct observation and by video recordings, in conjunction with a multichannel event recorder. Seven courtship behaviors were categorized: inspection from the substrate, aerial inspection, contact from the substrate, contact from the air, genital alignment, copulation, and male-male interaction. The frequency distribution of copulation bouts was best described by a Poisson distribution; peak mating activity occurred about 1 h into the bioassay. The duration in copulo, however, was extremely variable. On average, males spent approximately 30 s in copulo (n = 183); < 30% of bouts were > 50 s. The ability of males to discriminate between sexes, sexually immature and mature females, and between females of D. antiqua and the cabbage maggot, Delia radicum (L.), was most pronounced in the elements of genital alignment and attempted copulation. The courtship and mating behavior in D. antiqua is consistent with a sequence that relies initially primarily on indiscriminate visual recognition of a potential mate, followed by species- and sex-specific semiochemical recognition upon contact.