Oviposition Pattern of Early and Late-Emerging Genotypes ofDelia radicum(Diptera: Anthomyiidae) at Different Temperatures

Abstract

The cabbage maggot, Delia radicum L., has a bimodal pattern of emergence caused by the presence in populations of early and late-emerging genotypes that differ in their pupal development time. These genotypes could also express different egg-laying strategies. To examine oviposition patterns between genotypes and, particularly, their response to temperature, the egg-laying activity of females and egg mortality from each genotype were evaluated at temperatures from 12 to 30°C. Several criteria were used to describe the oviposition pattern: longevity of females, preoviposition period, lifetime fecundity, number of oviposition bouts, duration and number of eggs for each oviposition bout, duration of an oviposition cycle, and time interval between oviposition bouts. All criteria were similar between genotypes, except the preoviposition period and time interval between oviposition bouts. The preoviposition period was 1-4 d longer for the early emerging genotype than for the late-emerging genotype at temperatures <25°C, but similar at temperatures ≥25°C. The time interval between oviposition bouts of early emerging genotype was a few hours longer than for the late-emerging genotype at all temperatures. All oviposition pattern criteria responded to temperature, except the duration of oviposition bouts (≍6.5 d) and egg mortality (≍11%). The duration of a bout could be a compromise between oogenesis duration and the risks associated with egg deposition. According to these results, early and late-emerging genotypes express similar egg-laying strategies for all temperatures tested.

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