LOW WINTER TEMPERATURES AND THE POTENTIAL FOR ESTABLISHMENT OF THE EGG PARASITE ANASTATUS DISPARIS (HYMENOPTERA: EUPELMIDAE) IN ONTARIO POPULATIONS OF THE GYPSY MOTH

Abstract
The overwintering mature larva of the parasite Anastatus disparis Ruschka within the intact gypsy moth, Lymantria (= Porthetria) dispar L., egg chorion is susceptible to freezing and has a mean supercooling point of −28.8±0.14°C. This level of cold hardiness is not increased by exposure to sublethal low temperatures. Over 85% of larvae survived 10 months at 0°C and 4 days at −12° or −18°C, both followed by an additional 2–3 months at 0°C, but over half of the survivors went into prolonged diapause which was not fulfilled by subsequent rearing at room temperature. The parasite is apparently capable of surviving winter conditions over the same geographic area in Canada as the gypsy moth, and the introduction of A. disparts into locations in Canada where gypsy moth is now present is recommended.