Ecological studies on the black flies of the Souris River, Manitoba

Abstract

Nine species and one subspecies of black flies were collected in the Souris River. These were Cnephia dacotensis, Simulium johannseni, Simulium johannseni duplex, Simulium venustum, Simulium verecundum, Simulium tuberosum, Simulium vittatum, Simulium decorum, Simulium luggeri and Simulium meridionale. Five species, Simulium luggeri, Simulium meridionale, Simulium venustum, Simulium verecundum and Simulium johannseni are potential pest species. These five were observed to take blood meals from humans, cattle, horses and poultry. Simulium vittatum was the most abundant species. Simulium luggeri, Simulium meridionale and Simulium johannseni were less abundant than Simulium vittatum, but more numerous than Simulium venustum, Simulium verecundum and Simulium decorum. The least common species were Simulium tuberosum, Cnephia dacotensis and Simulium johannseni duplex... In an outbreak year, it appears that two larvicide treatments would be needed to control black flies in the Souris River... Four different artificial sampling devices were employed to collect black fly larvae and pupae. Of the four samplers tested; (cones, plates, ropes and wire cages), cone samplers are recommended for future larval population assessment in the Souris River. The characteristics that make cone samplers more desireable than the others tested include ease of handling, versatility and high performance in collecting immature simuliids. Comparison between samplers showed cone and plate samplers to collect significantly more black fly larvae and pupae than wire cage samplers. There was no significant difference in the collection of immature simuliids between cone and plate samplers. Rope samplers were note compared to the others because a true 2.5 cm2 sample not be obtained.