PHENOLOGY OF THE NATIVE PARASITOID SINOPHORUS MEGALODONTIS (HYMENOPTERA: ICHNEUMONIDAE) RELATIVE TO ITS INTRODUCED HOST, THE PINE FALSE WEBWORM (HYMENOPTERA: PAMPHILIIDAE)

Abstract

AbstractThe parasitoid Sinophorus megalodontis Sanborne is a univoltine endoparasitoid that attacks larvae of the pine false webworm, Acantholyda erythrocephala (L.). The morphologies of the egg, instar 1, and cocoon are described. Adult-emergence and Malaise traps were used to examine the patterns of adult activity in Ontario. Adults emerged from the soil over 17 d, in late May and early June, and the median emergence of males preceded that of females by 3.5 d. The sex ratio of emerging adults was approximately 1:1. Malaise traps collected more adults than did emergence traps and also provided information on adult flight period, but collections were biased towards captures of males. Dissections indicated that S. megalodontis oviposited in all instars of the host and that temporal and spatial variations occurred in coincidence with host instars. Encapsulation and superparasitism limited effectiveness of the parasitoids in reducing host populations. At the end of the larval period, the parasitism rate was 17.1%, but encapsulation reduced the effective rate to 9.0%. Superparasitism was observed in 4.8% of the host larvae. There was some indication that parasitism resulted in retardation of host development. Later-dropping host larvae had a significantly greater incidence of parasitism. The host is an introduced insect from Europe, whereas the parasitoid is likely endemic to North America. Few North American parasitoids attack this introduced species, and S. megalodontis appears limited in its ability to reduce the size of pine false webworm populations. Consequently, pine false webworm is a suitable candidate for classical biological control attempts with introduced parasitoids from Europe.