Orientation responses of individual larder beetles,Dermestes ater (Coleoptera, Dermestidae), to directional shifts in wind stimuli

Abstract

Anemotaxis in adult larder beetles, Dermestes ater,was investigated using a locomotion compensator, to uncover the mechanism(s) by which beetles maintain a course direction relative to a wind stimulus. Compared to walking in still air, anemotactically orienting beetles walk with the following characteristics over 60-s periods: (1) reduced locomotor and turning rates, (2) sustained, relatively straight paths with course directions at various angles to the wind, and (3) an increased tendency to stop for brief periods. Differences in wind speed affect mainly path straightness, which increases positively with stimulus intensity. Beetles “track” the wind direction equally well moving up or downwind, and they are able to orient at angles either close to the wind or at more oblique angles. When the wind direction was shifted 90°, the beetles turned, usually over the short angle, to their previous course heading relative to the stimulus. Indvidual beetles exhibited preferred course directions over several trials within a period of 20 min. Each beetle regained its particular anemotactic angle after the 90° shift in the stimulus direction. Although the beetles paused in some trials, stopping was not required to reorient to the altered stimulus direction.