Patterns of distribution of insects near a windbreak of tall trees

SUMMARY The distribution of shelter to leeward of a windbreak of tall trees was compared with the pattern of distribution of insects above and within a wheat crop. The pattern for flying insects blown from elsewhere resembled the shelter profile, in contrast to insects originating in the windbreak, which accumulated immediately behind the trees, and those originating a few metres to windward, which accumulated in a zone between 1/2 and 1 H (10–20 m) to leeward. These patterns were more distinct in direct than in oblique incident winds. The pattern of infestation of a breeding population of cereal thrips in the wheat resembled the distribution of airborne primary migrants 1–2 months earlier; the pattern of scatophagid flies on the crop also resembled that of airborne populations of other dung feeders originating slightly to windward of the trees.