The insect faunas of pear and apple orchards and the effect of windbreaks on their distribution

SUMMARY Two coir netting windbreaks, each 7 m tall and 46 m long, were erected in a pear and an apple orchard, to try to increase the number of insect pollinators present at blossom time. The flying insects were sampled with suction traps and insects visiting trees were sampled by examining marked clusters of blossom. The mean aerial density was calculated for each of the forty‐two taxa, mainly families, identified from the aerial population. There were about 50% more insects flying in the pear than in the apple orchard. The distribution of flying insects was greatly affected by the windbreaks, and the sheltered zone contained three times as many of most species, and more than three times as many Chironomidae, Psychodidae and Bibionidae as elsewhere. Small flies were the most abundant insects in the air, in both orchards. In the pear orchard large insects comprised only about 7 % of the total aerial population, of which honeybees constituted 0–7% and wild bees 0–3%. By contrast, large insects accounted for a greater proportion of the population on blossom. The reasons for this are discussed. On apple blossom Syrphidae and honeybees were the insects most often seen, and on pear blossom Bibionidae and Mycetophilidae.