Interactions between photoperiod and food affect the termination of reproductive diapause in Bruchus rufimanus (Boh.), (Coleoptera, Bruchidae)

Abstract

Bruchus rufimanus Boh. is a European bruchid developing at the expense of Vicia faba (L.) seeds. Studies in the wild have shown that the insect is univoltine. Adults present a reproductive diapause in the winter. The end of reproductive diapause results from interactions between increased duration of photophase and ingestion of pollen of the host plant V. faba. Of the two, photoperiod is the determinant parameter, since diapause does not terminate when the photoperiod is shorter than 16 h, whether or not there is feeding. The highest frequency of diapause termination is observed in 18 h light–6 h dark after consumption of the V. faba pollen. The pollen of V. faba is not only a trophic supply, but also a set of specific instructions leading to the termination of diapause, primarily in females. This interaction between climatic and biocenotic factors leads to a precise synchronization between the biological cycle of the insect and that of the host plant. Thus, females become sexually active as soon as the pods, which are the oviposition substrate, are available.