The immediate extraction and display of insect flight trajectories from infra-red remote sensing signals

Abstract

The increasing need to study insect flight behaviour in the natural environment has led to the development of a relatively inex- pensive remote sensing instrument (IRADIT) . Flying insects dfferentay iumjmted, under a light cmations, in a intense ba of pulsed near infra-red radiation and detected using a gated image intensifier - CIV system at a rate of 5OHz. This thesis details the methods employed for extracting insect oo-ordinates from the' CI video signals, 'using low~oost electronic circuits ad micro computer (Apple II+) , and for the immediate analysis and display of two-dimensional insect flight trajectories, whilst rejecting environmental and system noise. Flight trajectories are often dominated by the immediate local wind. A new low-cost sensitive three dimensional digital anemometer system hs be developed for use with the IRADIT system, providing the data required to allow the vector wind to b immediately subtracted and interesting aspects of flight behaviour to b revealed. The IRADIT - Anemometer system ws tested i the field, on insects above wheat. _ Small insects with membzßanous wing areas as small as 5mm2 were readily detected and tracked over distances of the order of l at ranges up t 15m against a mid-day sky background. Subse- quent computer analysis of stored insect track and wind data oonfirmed that the effects of immediate local wind cn b smdied or canoelled out. Examples of insect flight behaviour are described. The relatively low cost of the IRADIT system and the practical features in its design result in a powerful new tool for use by the field entomologist.