Experiments and observations of the near-host orientation and landing behavior of simuliidae (Diptera)

Bradbury, Wayne Claude (1972) Experiments and observations of the near-host orientation and landing behavior of simuliidae (Diptera). Masters thesis, Memorial University of Newfoundland.

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Abstract

Records of the seasonal succession and seasonal range of several species of adult female mammalophilic Simuliidae of insular Newfoundland are presented. -- Collections of mammalophilic Simuliidae on colored-shaped two-dimensional silhouettes indicated that various species orient and land on certain 'preferred' radiation compositions. The Prosimulium mixtum complex and Cnephia mutata were attracted consistently to black silhouettes; the Simulium venustum complex were attracted to silhouettes composed of 'blue' radiations while Simulium vittatum were orienting and landing on both red and black silhouettes. Black, 'blue' and red radiation compositions per ovdinem were most attractive while yellow was the least attractive for all species, which indicated that radiation compositions reflecting the least amount of light were the most attractive, but, depending on the species composition of the simuliid population, this generalization tended to become obscure. -- Responses of simuliiids to simple geometric shapes indicated individual contours were equally attractive while the various 'points of convergence' of the silhouette shapes attracted large numbers. -- Collections of flies orienting upwind to C0₂ obtained from a 'grid' of silhouettes indicated a decrease in the number of flies toward the row of silhouettes located downwind from the C0₂ point of emission. Depending on the individual silhouette 'colors' the flies were orienting to the C0₂ from as much as ten meters downwind. -- Simuliids landed on black, disc-shaped silhouettes of different areas in proportion to the surface area exposed. -- The responses of Simuliidae to 'attractive' and 'non-attractive' silhouettes and controlled release of gaseous C0₂ indicated a marked ability of simuliids to visually discriminate the targets largely on the basis of their individual radiation compositions and independant of the concentration of C0₂ or olfactory mechanisms. Discrimination coefficients indicated that distances approximating four meters downwind from the C0₂ source would appear to be a limiting distance for the simuliids' effective use of vision. -- Long-range, medium-range and near-orientation mechanisms are presented for the Simuliidae in terms of the sensory make-up through which they are mediated.

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