Studies on the auchenorrhyncha (hemoptera – insecta) of Pennine moorland with special reference to the ceropidae

Abstract

Notes on the autecology of 32 species of Auchenorrhyncha from the Moore House National Nature Reserve are given. Studies were made of the microclimates of the common vegetation types on which these occur and it is shown that the size and function as a temperature regulator of the spittle (produced by nymphs of the cercopidae) is associated with these gradients. Cercopid nymohs are shown to change feeding sites after moulting. The need to change host plants and thus leave protective spittle is thought to result in an increased mortality of nymphs (up to 3 per cent per day). Overall nymphal mortality is not dependent on population density. In two cercopids (Neophilaenus lineatus and Neophilaenus exclamationis), there are marked changes in population density in each year (1961 to 1963) and these are partly attributed to climatic factors. The hatch of cercopidae is delayed, and development is retarded at high altitides. Nymphal mortality rates in a cicadellid (macrosteles sexnotatus) and a delphacid (conomelus anceps) did not differ from those of the ceropidae studied, although they have no protective spittle. It is concluded that cercopid spittke is of some survival value at moore House by enabling the nymph to avoid parasites, if not predators, and unfavourable climatic conditions encountered whilst remaining stationary on the host plant during feeding. These advantages are not sufficient to give the Cercopidae a significantly higher survival rate than other Auchenorrhyncha at Moor House. Non-density dependent factors are thought to be responsible for a major part of the changes in population density. A compensatory mechanism at other stages of the life cycle has not been demonstrated. Local extinction at the edge of the range is a result of climatic factors. The population studied is probably below the density level at which regulating mechanisms may occur.