1989. Seasonal biology of Winthemia fumiferanae Toth. (Diptera: Tachinidae), a larval-pupal parasitoid of the spruce budwom (Lepidoptera: Tortricidae). Can. J. Zool. 67: 2384-2391. The phenology of Winthemia fumiferanue Toth. (Diptera: Tachinidae), a larval -pupal parasitoid of the spruce budwom, was studied in Quebec to evaluate its synchrony with the host. Adult emergence showed protandry and occurred when budworm larvae were in the second to the fifth instar. In Malaise trap catches, males were dominant during the emergence period but as this ended, females became dominant and remained so for the rest of the season. Females emerged with undeveloped ovaries and abundant fat reserves. The maturation of eggs was completed within 2 weeks after emergence and coincided with the appearance of sixth-instar budwom larvae. Potential fecundity was correlated with female body size. Females deposited, on average, 32% of potential eggs, many oocytes remaining undeveloped in the ovarioles. Oviposition on spruce budwom larvae was synchronized with peak abundance of the sixth instar. Winthemia fumiferanae prepupae, among other dipteran parasitoids of the spruce budwom, were the last to drop to the ground. There was evidence of a partial second generation but its incidence was below 1 % under field conditions. More than 95 % of the W. fumiferanae puparia were found between 0 and 40 mm below the soil surface. The importance of W. fumiferanae in spruce budwom outbreaks and factors that may reduce its efficacy as a mortality agent are discussed.HBBERT, C., CLOUTIER, C., RBGNIBRE, J., et PERRY, D. F. 1989. Seasonal biology of Winthemia fumiferanue Toth.(Diptera: Tachinidae) , a larval -pupal parasitoid of the spruce budwom (Lepidoptera: Tortricidae) . Can. J . Zool. 67 : 2384-2391. La phknologie de Winthemia fumiferanae Toth. (Diptera: Tachinidae), un parasitoide des larves et des chrysalides de la tordeuse des bourgeons de l'kpinette, a kt6 CtudiCe au QuCbec dans le but d'Cvaluer son degd de synchronisme avec l'h6te. L'Cmergence des adultes Ctait caractCrisCe par la protandrie et a debut6 durant le deuxikme stade larvaire de la tordeuse pour se teminer au dCbut du cinquikme. Dans des captures effectuCes h l'aide de pikges Malaise, les miles Ctaient dominants pendant la pCriode d'imergence des adultes, puis les femelles ont dominC pour le reste de la saison. Lorsqu'elles Cmergent, les femelles ont les ovaires peu dCveloppCs et d'abondantes rkserves de graisse. La maturation des oeufs a Ct C complCtCe en 2 semaines et a coYncidC avec l'apparition des larves de sixikme stade. La fCconditC potentielle Ctait relike h la taille des femelles. En moyenne, les femelles ont pondu 32% de leurs oeufs potentiels; beaucoup d'oocytes sont restCs immatures dans les ovarioles. La ponte sur les larves de la tordeuse etait synchroniske avec l'abondance maximale des larves de sixikme stade. Parrni les autres diptkres parasitoides de la tordeuse, les pr6-pupes de W. fumiferanae ont Ct C les dernikres h tomber au sol. Nous avons observC une deuxikme gC...