Ecology and Declining Status of the Silver-Spotted Skipper Butterfly (Hesperia comma) in Britain

Abstract

(1) A survey was made of all British colonies of Hesperia comma, which revealed that it had declined to about forty-nine populations, most of which were small. (2) Adult H. comma proved to be very particular when egg-laying. They preferred small Festuca ovina plants that were largely surrounded by bare ground or scree, and which also grew in sheltered sunspots. Most F. ovina growing on most sites were rejected as unsuitable, and the adult population density of H. comma was correlated with how closely the sward approached the ideal structure for egg-laying. (3) Most sites that had lost H. comma still contained abundant F. ovina, but were too overgrown to be suitable for breeding. Most extinctions of H. comma occurred during a twenty-year period, when many unfertilized downs in Britain became overgrown after rabbits were killed by myxomatosis. (4) The habitat on several former sites has improved for H. comma since the late 1970s, due to a recovery by rabbits and some sheep stocking on abandoned downs. To date, H. comma has only spread to re-occupy sites that were within 4 km of existing colonies. The natural recolonization of other sites may take decades or centuries. (5) Conservationists could dramatically improve the status of H. comma by making artificial introductions to unoccupied sites. A high proportion of the existing colonies are already on nature reserves, but one-quarter of 'protected' populations had become extinct by 1982, due to inadequate grazing.