The Hemiptera of two sown calcareous grasslands. II. Differences between treatments.
In field studies in the UK, Hemiptera were sampled using vacuum nets from replicated sown swards of 2 contrasting types, a fine-leaved grass mixture and a coarse one. Samples were taken in late autumn and winter 1973 and throughout 1974 and 1975. Species richness of grassland Heteroptera was low and few differences between treatments were observed. Significantly more heteropterous insects overwintered in the coarse grassland than in the fine, with consistent, significant differences between treatments for Notostira elongata and Nabis ferus. Auchenorrhyncha were more abundant on the coarse grassland in 1974, but on the fine grassland in 1975. Species richness, equitability, and especially diversity, were higher on the coarse sward. The fauna of the coarse grassland tended to be more diverse at any one time, but cumulatively the fauna of the fine sward was slightly more diverse. Seven species were predominant on the coarse grassland and these included Neophilaenus lineatus, Cicadula persimilis, Stenocranus minutus, Zyginidia scutellaris and Javesella pellucida (in the 2nd generation only); the last 4 species were abundant. Seven species were also predominant on the fine grassland and these included Deltocephalus pulicaris and Euscelis incisa; none of the predominant species was abundant, and significant differences between treatments were observed only in 1975 for 3 of them. A few species showed a response to the 2 grassland types which varied in time. Arthaldeus pascuellus [Sorhoanus pascuellus] was significantly more numerous on the coarse sward in summer 1974, but much more abundant on the fine sward in summer 1975. The results are discussed in relation to the known feeding requirements of the species and to the establishment of grassland swards for nature conservation. It is concluded that mixtures of many grass species should be used to establish patches of grassland of variable structure and composition.