Factors influencing nuisance blackfly (Diptera: Simuliidae) activity in the Scottish Highlands.

The nuisance activity of blackflies (Diptera: Simuliidae) was investigated in several habitats on Speyside, near Kincraig (57 degrees 08'N, 3 degrees 56'W), Invernesshire, in central Scotland during May-October 1987-89. The main blackfly species caught landing/biting on humans were Simulium reptans, S. argyreatum, S. variegetum and the S. tuberosum complex, in order of prevalence. Blackfly biting activity occurred from mid-May to mid-September. Numbers of female blackflies attracted to volunteers were correlated with their body posture, habitat and the season. Overall, Simulium activity was greatest in mixed birch/juniper forest, least in spruce plantations and at intermediate levels on pasture, moorland and in Scots Pine forest. Compared with an adult, a child experienced twice as many Simulium bites per hour (12.2 v 6.3) in the birch forest. On the child's body, 69% of blackflies landed on the head, neck and back, whereas the majority landed on the legs (48%) and arms (28%) of adults. Bending over, especially during the exertion of gardening, was more attractive to anthropophilic blackflies than standing or kneeling.