The effects of an artificial windbreak on the aerial distribution of flying insects

Abstract

SUMMARY Suction traps were used to measure the aerial density of insects near a low, slatted wooden fence on an otherwise exposed plot. When winds blew approximately at right angles to the fence insects gathered in the air near to it, especially to leeward, where they were from 2 to 27 times as concentrated as elsewhere. The increases in concentration extended farther to leeward for day‐flying insects than for night‐flyers. These accumulations were caused mainly by wind, and turbulence in the incident air stream had a greater influence than wind velocity. The relative density profiles for winged insects, spiders and inert particles measured near the fence had much the same pattern except that, close to the fence, the insects and spiders were more concentrated than the particles; strong day‐flying insects gathered to leeward in greater numbers than weak day‐flyers or night‐flyers.