The seasonal activity of hematophagous Diptera attacking cattle in insular Newfoundland

Simuliidae comprised 94.1% of about 20 000 biting flies (in 26 species) collected in a cattle-baited trap and a Trueman-McIver segregating CO2 trap in Newfoundland in May-September 1982; mosquitoes, ceratopogonids and tabanids formed the remainder. Blood-fed flies represented 54.7% of the total catch in the cattle-baited trap, but the proportion varied considerable among species. Simuliid activity was concentrated in June and July, although these flies were also collected in May, August and September. Prosimulium mixtum was the predominant species in June, and species of the complex of Simulium venustum and S. verecundum were the major pests in July. P. mixtum was most active from mid-morning to late afternoon. The Simulium complex showed a peak of activity in the morning and another in the early evening. A few examples of P. mixtum and the Simulium complex were active after dark. Significant correlations were found between the numbers of flies collected in the 2 traps for P. mixtum and the complex of S. venustum and S. verecundum. The remaining species were taken in numbers too low for analysis.