Night flight towards a sex pheromone source by male Spodoptera littoralis (Boisd.) (Lepidoptera, Noctuidae)

Abstract

PHEROMONES have been used in population monitoring traps¹ and in control by ‘confusion’², and a good understanding of how the male finds the female is of great practical importance in the development of these techniques. The problem of insect orientation towards distant odour sources is also intrinsically interesting and much work has been done with wind tunnels to study the flight of moths in attractant plumes (the most recent of many reports is ref. 3). These studies have shown that moths fly upwind in a series of horizontal zig-zags which decrease in amplitude as the source is approached. Field observations support these general findings⁴, but they are not as detailed as the results of laboratory studies and the techniques are not suitable for night flying species, many of which have considerable economic importance. We describe here techniques for observing and recording the details of the behaviour of night flying insects in attractant plumes, and also some new findings which suggest that flight towards a sex pheromone source in one species consists of several distinct stages with deviations from a straight upwind path taking place largely in the vertical plane.