The influence of parasitism on the life history of a high arctic insect, Gynaephora groenlandica (Wöcke) (Lepidoptera: Lymantriidae)

Abstract

The life history of Gynaephora groenlandica was studied in the high arctic at Alexandra Fiord, Ellesmere Island. Life history events (larval development, pupation, adult emergence, mating, oviposition, hatching, and moulting to the second larval instar) occurred only in the 3–4 weeks before mid-July. Larvae fed mainly on Salix arctica. They stopped feeding by the end of June, hid, and spun hibernacula. Nineteen percent of third- and fourth-instar larvae were parasitized by the wasp Hyposoter pectinatus (Ichenumonidae); 52% of fifth- and sixth-instar larvae and pupae were parasitized by the fly Exorista sp. (Tachinidae). We estimated that G. groenlandica has a life cycle lasting 14 years. Parasitism caused 56% of overall mortality, whereas cumulative winter mortality was calculated as 13% of a cohort passing through a 14-year life cycle. Peak of activity of adult parasitoids coincided with inactivity of Gynaephora larvae during July. Selective pressure of parasitism may restrict development of G. groenlandica to a short period before adult parasitoids are most active. The importance of parasitoids in the life history of G. groenlandica suggests that parasitism is as significant as climate in population regulation of insects living in the high arctic.