The use of attractants and repellents in vector control.

A great many stimuli-auditory, visual and chemical-attract or repel insects and some of these play an essential role in maintaining the life of the individual or perpetuating the species. The author examines the modes of action of attractants in nature, particularly in relation to blood feeding. The predominant mechanism of attraction to an odour source (e.g., in host finding) appears to be positive anemotaxis. Success in locating the source is influenced by wind conditions and by the visual acuity and field of view of the insect. The author considers the physical and chemical properties of materials that have been widely used as attractants and repellents and indicates the unsatisfactory nature of present theories to explain their action. Possible applications of attractants in vector control include their use in traps, baits and sprays, while repellents are mainly of value for personal protection. Increased understanding of the mechanism of action is likely to lead to the development of much more effective materials and to their wider application.