Developmental threshold, day-degree requirements and voltinism of the aphid predator Episyrphus balteatus (Diptera: Syrphidae).

摘要

Episyrphus balteatus is the dominant syrphid predator of aphids in the UK; re-establishment of populations each season is mainly by migration from warmer climes, as overwintering in this country is minimal with an uncertain level of success. The effects of temperature on the developmental rate of E. balteatus were investigated to determine the potential voltinism of this species in the UK. Estimates of the developmental threshold temperature from oviposition to adult emergence varied between 6.0 and 7.1鳦 with a day-degree (DD) requirement of between 256 and 280 depending on the method of analysis used. Using the DD requirement derived from a weighted linear regression (261 DD above a threshold of 6.8鳦) in combination with the required value fromadult emergence to first oviposition, a total requirement is suggested of approximately 374 DD above 6.8鳦 per generation. These data, together with climate records, indicate that 1-3 generations are possible each year, depending on the available DD andorigin of the population. The advantages and limitations of different approaches and models used to estimate developmental thresholds and DD requirements are discussed.