The distribution of flying insects near a low hedgerow.
The following is virtually the author's summary. The patterns of distribution, of insects flying over pasture, to leeward of a mixed hedge in southern England were measured with suction traps [cf. RAE A 55 2417-2419, etc.]. Insects in the hedgerow and neighbouring fields were sampled with a vacuum sampler to show the probable origin of some taxa within the aerial populations. The patterns for insects drifting over the hedge from distant sources resembled patterns near artificial windbreaks of similar permeability, with accumulations extending about ten times the height of the hedge to leeward and with the greatest density at about 2-4 times the height of the hedge to leeward. Patterns for insects originating in the hedge were quite different, with accumulations extending a shorter distance to leeward and with the greatest densities immediately behind the hedge. Whatever their origin, fewer insects accumulated in slow winds than in fast, which suggests that accumulations near hedges occur largely because the patterns of air-flow created by the hedge concentrate insects from the passing aerial population, and not because the hedge itself supplies the greater population.