Effect of temperature on the biology of Harmonia dimidiata FAB. (Coleoptera: coccinellidae) reared on scizaphus graminum (ROND.) aphid

The influence of five constant temperatures (16±1°C, 20±1°C, 24±1°C, 28 ±1°C and 32 ±1°C) on the biology and prey consumption of larvae, adult male and female beetles of the ladybeetle, Harmonia dimidiata (Fab.), (Coccinellidae: Coleoptera), feeding on Schizaphus graminum aphid was investigated. There was significant effect of temperature on the biology and prey consumption potential of immature and adult stages of H. dimidiata. The result revealed that incubation period, different larval instars duration, pupal and adult male and female beetles duration was maximum at the low temperature 16 ± 1˚C and minimum at the high temperature 32 ± 1˚C. The survival rate and predatory potential of all stages was maximum at 24 ± 1 ˚C. The female fecundity was maximum 686.75±18.277 eggs per female at 24 ± 1˚C and minimum 223.75±4.3279t 28 ± 1˚C. The results further revealed that at 32± 1˚C the female could not produce eggs. The result indicates that temperature have profound effect on the developmental durations, survival, fecundity and predatory potential of Harmonia dimidiata. The optimum rearing temperature for this predator was found to be 24 ±1°C on the basis of their short durations, maximum survival and high reproductive and predatory potential of H. dimidiata (Fab.). These attributes may take it a useful natural enemy for the purpose of biological control program against aphid pests of economic importance.本研究探究了五种恒温条件（16±1℃、20±1℃、24±1℃、28±1℃及32±1℃）对取食麦二叉蚜（Schizaphus graminum）的孪斑瓢虫（Harmonia dimidiata (Fab.)，鞘翅目（Coleoptera）瓢虫科（Coccinellidae)）幼虫、雌雄成虫的生物学特性与捕食量的影响。温度对孪斑瓢虫未成熟期及成虫期的生物学特性与捕食潜能均存在显著影响。研究结果显示，卵期、各龄幼虫历期、蛹期及雌雄成虫寿命在16±1℃的低温条件下达到最长，而在32±1℃的高温条件下最短。各虫态的存活率与捕食潜能均在24±1℃条件下达到最高。雌成虫繁殖力在24±1℃条件下达到最高，单雌产卵量为686.75±18.277粒；在28±1℃条件下最低，单雌产卵量为223.75±4.3279粒。进一步研究发现，在32±1℃条件下，雌成虫无法产卵。上述结果表明，温度对孪斑瓢虫的发育历期、存活率、繁殖力及捕食潜能均具有显著影响。综合发育历期较短、存活率最高以及繁殖与捕食潜能较强等指标，本研究确定该捕食性天敌的最适饲养温度为24±1℃。该瓢虫的上述优良特性使其可作为防治具有经济重要性的蚜虫害虫的生防天敌，应用于生物防治项目中。