Studies of host location behaviour in the black fly Simulium arcticum (IIS-1O.11) (Diptera: Simuliidae): aspects of close range trap orientation

Abstract

AbstractField studies of orientation responses of the IIS-10.11 sibling of Simulium arcticum Malloch species complex and other simuliid species to host-mimicking cattle silhouette traps (CSTs) were carried out in the Athabasca region of Alberta, Canada. Simuliids were attracted to CSTs from downwind by a CO2 bait but very few were attracted to an unbaited CST. Passively searching simuliids tended to fly at lower levels than actively host seeking ones. Simuliids appeared to fly at lower levels when within visual range of the CST than when outside of it. Higher flight levels may improve chances of eventually making visual contact with the host or CST. Experiments in which a CO2 outlet was separated by increasing distances from a CST indicated that simuliids see the 1.1 m long CST at a range of approximately 8 m. Simuliids landing on the CST, whether CO2-baited or not, showed a strong preference for the trap's ends followed by the downwind side, followed by the upwind side. Species composition of collections from CST collections differed significantly from the species composition of cattle sweeps taken at the same times. Simulium vittatum was over-represented in collector catches in comparison to cattle sweeps. This bias may be due to species-specific differences in responses after landing on the CST since sweeps taken around CSTs had compositions similar to cattle sweeps. Results are discussed in terms of host orientation in biting flies in general and the suitability of CST-type traps as components of attractant-based control strategies and in simuliid population monitoring.