PROTANDRY IN DELIA-ANTIQUA (DIPTERA, ANTHOMYIIDAE)

Set differences in the duration of egg-larval and pupal stages, and in eclosion curves were examined under 3 different temperature regimes i n the laboratory to assess the likelihood of protandry as an adaptive strategy for tile onion maggot, Delia antiqua (Meigen). Significant se x differences in development time of larval and pupal stages were evid ent when eggs were reared at constant (22 degrees C) or alternating (1 2-22 degrees C) temperature. When male egg development was delayed 24 h by storage at 4 degrees C, followed by 22 degrees C, mean larval dev elopment time was significantly greater, but pupal biomass and develop ment time were significantly lower suggesting variation in relative la rval growth rates between the sexes. Under nondiapause conditions, mal e pupae weighed significantly less than females, but pupal weight was only weakly correlated with larval development. Eclosion of diapause m ale pupae occurred over a shorter interval (4 d) than from nondiapause pupae (9-12 d), but protandry resulted from disparate pupal developme nt times between the sexes alone, because sexual dimorphism of pupal w eight was not apparent. The hypothesis that protandry is an adaptive s trategy providing reproductive benefits to either sex is equivocal for D. antiqua because eclosion curves of pupae were normally distributed and mean time lags in eclosion peaks between the sexes were too short (4 d) to optimize any reproductive benefits from early sexual maturat ion or mating. The alternative hypothesis is presented that protandry is a nonadaptive outcome of selection for other life history traits th at is unbiased by female size dimorphism.