Reproductive patterns of the European corn borer (Ostrinia nubilalis) in Alberta

Males and females of Ostrinia nubilalis (Hübner) from Alberta were held at constant and variable temperatures within a 17–32 °C range to determine the effect of temperature on longevity, daily oviposition, egg viability, total fecundity, reproductive period, and oviposition rate. The lower developmental thresholds and thermal summations for each stage were calculated from linear regressions. Moths from the South Saskatchewan River valley laid significantly more eggs over a longer period than those from the surrounding plains. The upper threshold for oviposition was higher (27 °C) for valley than for plains borers (25 °C). Optimum temperatures for egg viability were also higher for valley (25–27 °C) than for plains borers (22 °C). Fluctuating temperatures increased survival of both sexes compared with equivalent constant temperatures. Differences in male and female longevity likely arose in response to selection for different reproductive strategies in each sex. Long-lived individuals achieved high fecundity by reproducing at a low rate over many age-classes, while short-lived individuals reproduced at a high rate over few age-classes, with less total fecundity. Fecundity and reproductive period in the corn borer are plastic phenotypes that can change rapidly under differing environments.