Overwintering behaviour of Diphyus quadripunctorius (Müller) (Hymenoptera: Ichneumonidae, Ichneumoninae) in south-east Scotland

Abstract

Overwintering behaviour of adult females of the ichneumonid Diphyus quadripunctorius (Müller) in caves and mines in south east Scotland was monitored over two successive winters. This is a univoltine larva-pupal parasitoid of certain Noctua species, parasitizing their larvae in spring. The species was found in rather few of the sites investigated, but in one site in particular it was numerous. There the species was present over the period mid-July until the end of March. It remained semi-active through the winter in all these subterranean sites, some of which were prone to flooding. The ambient temperatures were always well above freezing, which probably allowed the insects to move to safety, although some drowned individuals were found. Wider data drawn from the National Museums of Scotland collection suggest that, in S. Europe as well as in Britain, D. quadripunctorius enters the sites in which it will eventually overwinter rather soon after emergence from its host pupae in early to mid-summer.