The effects of seasonal grazing on the Heteroptera and Auchenorhyncha (Hemiptera) of chalk grassland.
Samples of Heteroptera and Auchenorrhyncha were taken from replicated plots grazed by sheep in spring, summer, autumn and winter and from ungrazed areas of chalk grassland at a Nature Reserve in central England in August 1968 and from May 1969 to August 1971. Thirty-five species of Heteroptera and 49 of Auchenorrhyncha were recorded. There was no marked aggregation of individuals on any plot. Fewer nymphs of both groups were taken in July on the plots grazed in spring compared with the others. Numbers of both groups, and the numbers of species represented, tended to be higher on the autumn- and winter-grazed plots than on those managed in spring and summer. The ungrazed grassland supported greater numbers of individuals and more species than the managed plots. Species diversity of the Auchenorrhyncha samples did not differ markedly between treatments, but was greater than expected on the grazed plots. The results are discussed in relation to the practical management of chalk grassland nature reserves. Autumn or winter grazing is preferred to spring or summer grazing when other considerations permit. Annual grazing is inferior to rotational grazing for maintenance of species richness of Hemiptera.