Use of Shadows for Studying the Three-Dimensional Structure of Insect Swarms

A photographic technique is described for determining the three-dimensional position of swarming midges. The procedure is applied to the midge, Anarete pritchardi Kim, which swarms in the daytime, preferably under clear skies 3–5 cm above a white surface or a swarm marker. The midges cast their shadows on the marker, and the shadow combined with midge's real image on film can be used to estimate the height of the flying insect.