The habitat requirements of adults of the Wart-biter Decticus verrucivorus (L.) (Orthoptera: Tettigoniidae) in Southern England

Abstract

The large ground-dwelling bush cricket, Decticus verrucivorus (L.) (Orthoptera: Tettigoniidae) has only four populations in southern England. As such, it is one of Britain's most endangered insect species. This paper describes the distribution of final instars and adults in relation to vegetation structure within the chalk grassland supporting Britain's largest population. The results are discussed in terms of management recommendations for the species' conservation. The vegetation was predominantly below 5 cm in height, but comprised a mosaic of vegetation types, such that sampling units of 25 m 2 typically contained both close-cropped turf and tussocks. Both developmental stages were found predominantly in patches of tussocky vegetation which had a height of around 20 cm and covered 25% of the study site. The distribution of male final instars and male adults was similar. However, adult females were found more frequently in areas of short, open turf than male adults or final instars. Consideration of the species' egg-laying behaviour suggests that adult females were leaving the shelter of grass tussocks to oviposit in adjacent open areas with small patches of bare soil. A mosaic of vegetation structures may also be important in enhancing mate location when population density is low, because propagation of male song is greater over short turf than through dense vegetation. Although these findings are relevant to management practice, it must be stressed that an appropriate policy should include a consideration of the requirements of all stages of the life cycle.