THE PARASITISM OF BLACK FLIES (DIPTERA, SIMULIIDAE) BY LARVAL WATER MITES MAINLY OF THE GENUS SPERCHON

Abstract

Larval sperchonid hydracarina, possibly Sperchon jasperensis Marshall, parasitized adult simuliids in Canada. All stages of the water mites were found during the summer. Larval mites gained access to adult black flies as they emerged. Parasitism occurred from spring until fall, reaching a peak in July in Algonquin Park, Ontario, and in August at Baker Lake, N.W.T. Diurnal changes in parasitism followed the pattern of emergence of the infested simuliid species. Larval mites that had doubled in size as parasites regained the water as the female flies were ovipositing. Some simuliid species were more attacked than others, and females more than males, observations which appear related to the amount of nutrient stored in the fly. This nutrient may benefit the parasites directly, or benefit them indirectly because flies with more nutrient more quickly complete the adult phase of their cycle. The most important bloodsucking species of black flies were the least infested by sperchonid mites.