Field and laboratory observations on a cytoplasmic polyhedrosis virus of blackflies (Diptera: Simuliidae)

Larval blackflies were sampled from streams in Newfoundland, Canada, from April 1974 through October 1975 for the presence of cytoplasmic polyhedrosis virus (CPV). CPV was found in Cnephia mutata, Prosimulium mixtum fuscum, Simulium tuberosum, S. venustum, and S. vittatum. Virus was most common in C. mutata occurring in seven of nine streams from which this host was sampled and with an incidence of infection up to 54%. Infections were rarer in other species, occurring in 10–30% of the streams sampled, depending on host species. Incidence of infection was usually less than 1% and never exceeded 5% for any species other than C. mutata. Results of preliminary infectivity studies are given, and the bionomics of the disease in nature are discussed.