On the biology of Cnephia ornithophilia and Simulium vernum (Diptera: simuliidae) in insular Newfoundland

Okaeme, Augustine Nkadi (1983) On the biology of Cnephia ornithophilia and Simulium vernum (Diptera: simuliidae) in insular Newfoundland. Masters thesis, Memorial University of Newfoundland.

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Abstract

The habitat and life history of Cnephia ornithophilia, Davies, Peterson and Wood; and Simulium (Eusimulium) (vernum) (Macq) were investigated in 49 streams in order to characterize the habitat and larval distribution. -- Cnephia ornithophilia larvae were restricted to pond outlets feeding in small permanent streams in forested areas. The distribution of larvae indicated a relatively broad range of conditions in terms of stream width, depth, current velocity and substrate choice. This species is univoltine, and eggs begin to hatch in September. There are eight larval instars with a prolonged period of development (September to May). The larvae formed clumps, were sedentary, and relocate to the undersurface of substrates in winter, while physio-logically the growth rate between instars is highly variable and they have a wide thermal tolerance (0-30°C). -- Simulium vernum larvae are more widely distributed in streams than C. ornithophilia, occurring both at pond outlets and elsewhere in temporary and permanent streams both in forested and barren areas. These streams ranged from small tricklets to streams up to 3 m wide. The local species is cytotype "B" and bivoltine with the first generation from May to July and the second generation July to August. -- Using emergence and bantam-baited traps it was found that C. ornithophilia emerges in May, only during the day (1500 - 1900 h) when stream temperature is 10-12°C. Host seeking females were anautogenous limited to the forest and between 1300 - 2000 h. Oviposition apparently occurs within pond near the outlet, based on location of first instars. -- Simulium vernum emerges in June (1100 - 1900 h), and in August (0900 - 1300 h), for the first and second generation respectively. Host seeking females are anautogenous with activity within forest and forest fringes between 9000 - 2000 h. The prevalence of Leucocytozoon in females was 19.04%, with a high attack and blood feeding rates, indicating a good vector. Oviposition is along streams near sunset (1700 h). -- Although the seasonal occurrence of C. ornithophilia and S. vernum is later and prolonged in Newfoundland, they are ecologically similar to populations occurring elsewhere on the continent.

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