Life‐History Traits and Overwintering of Actia interrupta (Diptera: Tachinidae), a Larval Parasitoid of

ABSTRACT

Actia interrupta (Diptera: Tachinidae) is an important larval parasitoid of the eastern spruce budworm, Choristoneura fumiferana (Lepidoptera: Tortricidae), especially during low‐density (endemic) population phases. Despite its ecological importance, information on its basic biology remains limited. In a laboratory study, we described the morphology and development of immature stages, measured the duration of development at different temperatures, adult longevity, and the temporal dynamics of egg and larval maturation in females. Females were confirmed to be larviparous, larvipositing first‐instar larvae following a post‐copulation gestation period. The parasitoid develops through three larval instars, with the final instar forming a secondary respiratory funnel within the host prior to egression. Development time decreased with increasing temperature, while adult longevity was not affected by sex or mating status. Behavioral assays showed that females preferentially flied, landed, and larviposited on substrates containing hosts, supporting an indirect larviposition strategy. Finally, we demonstrate for the first time that the oblique‐banded leafroller, Choristoneura rosaceana (Lepidoptera: Tortricidae), serves as a suitable overwintering host for A. interrupta . These results provide key biological insights into a parasitoid species contributing to the regulation of low‐density spruce budworm populations.