An analysis of colour effects in the performance of the F2 trap against Glossina pallidipes Austen and G. morsitans morsitans Westwood (Diptera: Glossinidae)

Abstract

F2 traps of 53 different colours, selected from measurements of spectral reflectivities in the colour range visible to Glossina, were tested in a field study against G. morsitans morsitans Westwood and G. pallidipes Austen in Zimbabwe. Trap effectiveness depended mainly on reflectivity in four different wavelength bands, two of which, blue-green and red, were positively correlated with trap score; and two of which, ultraviolet and green-yellow-orange, were negatively correlated with trap score, the most important effects coming from the blue-green and green-yellow-orange bands. The ‘best’ trap material was a royal blue cotton, which reflected blue-green strongly but very little ultraviolet or green-yellow-orange. This material together with the lowest-scoring colours (green and yellow) gave results outside the range of a set of grey traps, indicating that the flies employ colour information and not intensity-contrast information alone in trap- orientated behaviour. No significant differences in colour preferences were found between sexes or species.