A14: Packer, L. 1988. The effect of Bombylius pulchellus (Diptera; Bombyliidae) and other mortality factors upon the biology of Halictus ligatus (Hymenoptera; Halictidae) in southern Ontario. Canadian Journal of Zoology. 66:611-616.
Abstract: Two factors were important in causing brood mortality in a southern Ontario population of Halictus ligatus: parasitism by larvae of the bombyliid Bombylius pulchellus and various forms of microbial infection of bee immatures or their pollen ball food. Bombyliid larvae consumed host prepupae or, less commonly, young pupae, restricted their attack mostly to the reproductive brood, and were contagiously distributed within the nest population. All immature stages were susceptible to fungal infection or disease but such pathogens did not seem to spread among cells within nests, indicating that bees may be able to prevent the spread of disease from one brood cell to another. Filling affected cells with earth may accomplish this brood hygiene. The survival rate of worker and reproductive brood immatures approximated 90%. Reproductive brood mortality affected females more than males. Reproductive brood mortality was probably underestimated: filled-in cells that may represent brood mortality were not included in these estimates.