Drew Carleton

We examined patterns of host exploitation by natural populations of three Telenomus species (Hymenoptera: Scelionidae) parasitizing hemlock looper, Lambdina fiscellaria Guenée (Lepidoptera: Geometridae), eggs in sentinel traps in eastern Quebec and western Newfoundland (Canada). The percentage of eggs parasitized by Telenomus flavotibiae Pelletier and Telenomus coloradensis Crawford in autumn, and by Telenomus droozi Muesebeck in spring either were not or only weakly related to host egg density. In contrast, the percentage of eggs parasitized by T. coloradensis in the spring was positively related to host egg density. Telenomus flavotibiae and T. droozi parasitized eggs in fewer traps than T. coloradensis, suggesting that they were less abundant or less efficient locating host patches. Eggs parasitized by T. droozi only occurred in traps with eggs parasitized by T. coloradensis, suggesting that it may be responding to kairomones emitted by T. coloradensis. In contrast, neither the number nor sex ratio of T. coloradensis emerging from eggs in traps with T. droozi differed from those in traps without this congeneric. Secondary sex ratios of all three species were significantly female biased. Our study suggests that only T. coloradensis has the potential to regulate hemlock looper populations.

A 2-year field study was conducted using sentinel traps to determine the seasonal distribution of the egg parasitoid (Hymenoptera) complex attacking hemlock looper, Lambdina fiscellaria (Guenée), throughout eastern Quebec and western Newfoundland. Hemlock looper populations remained low in all areas over the course of the study. Parasitism of eggs in sentinel traps was generally lower in fall than in spring. Trichogramma Westwood (Trichogrammatidae) as well as Telenomus flavotibiae Pelletier and an unidentified species of Telenomus Haliday (Scelionidae) only parasitized eggs in the fall. Telenomus droozi Muesebeck only parasitized eggs in the spring, whereas T. coloradensis Crawford attacked eggs during both fall and spring. Telenomus coloradensis was the most abundant parasitoid species collected and was far more abundant in spring than in fall collections.