Role of visual stimuli in host and mate location of the Colorado potato beetle

Visual responses of adult male and female Colorado potato beetles CPB, Leptinotarsa decemlineata (Say) (Coleoptera, Chrysomelidae) to 10 x 20 cm coloured paper-boards, beetle-sized coloured beads or dead CPB, and to combinations of these in laboratory experiments in an arena of 52 cm diameter were investigated. In addition, visual discriminatory abilities of males exposed to female-specific substances were also measured. The paths of the beetles were recorded on videotape by a computer-aided motion detection system. Parameters of tracks were calculated and the tape-recorded paths were further processed for behavioural analyses and for obtaining mean angular directions by circular statistics. Both sexes showed a strong preference for yellow-black striped, yellow and light-green boards and, to a lesser degree, were also attracted to yellow-green, dark-green, red and white boards, to beetle-sized beads coloured either black or yellow-black striped, and to some combinations of these. Males exposed to female substances immediately prior to entering the arena performed significantly more successful approaches to objects than did males of the control group. These results corroborate field observations on males' mate-searching behaviour and increase our understanding of natural host- and mate-finding processes.