The occurrence of some endoparasites of blackflies (Diptera: Simuliidae) in insular Newfoundland

Abstract

In 1971 and 1972, simuliids from 198 streams along the Trans-Canada Highway and Avalon Peninsula in insular Newfoundland were examined for endoparasites. The mermithids Gastromermis viridis, Isomermis wisconsinensis, and Neomesomermis flumenalis were recovered from blackfly larvae in 59 streams. The first two species were of restricted occurrence, recovered from only 8% of the streams carrying mermithids; N. flumenalis was widespread and is the most important mermithid parasite of Newfoundland simuliids. Five species of microsporidans (Thelohania bracteata, T. fibrata, Pleistophora simulii, Caudospora simulii, and C. brevicauda) were obtained from simuliids in 40 streams. Caudospora simulii and C. brevicauda were collected from overwintering larval simuliids; the remaining three species were obtained from spring and summer generation larvae. The fungal parasite Coelomycidium simulii was recovered from both overwintering and summer larvae in 14 streams. Both fungal and microsporidan parasites were widely distributed over the island.