Published online by Cambridge University Press: 10 July 2009
A description is given of the use of a video camera to estimate light-trap efficiency in the field. This camera relies on the extra light sensitivity provided by the Newvicon detector tube to enable insect track discrimination. Recorded insect flight tracks were classified into three distinct categories, new arrivals, passers by and local flights, the numbers of which were compared to the moth catch in a Robinson mercury vapour light-trap. Calculations of efficiency were made using two methods, the best-estimate efficiency, obtained by comparing the new-arrival tracks to the light-trap catch, and the worst-estimate efficiency, obtained by comparing new-arrival tracks plus passer-by tracks to the light-trap catch. Preliminary results indicate that efficiency varies with windspeed but with a maximum of 39%, obtained in virtually calm conditions, suggesting that some aspect of moth behaviour limits trapping efficiency. It is suggested that the speed of migration of screening pigment from the dark-adapted state to the light-adapted state in superposition eyes may have a bearing on the catching mechanism of a light-trap.