The ecology and conservation of the chequered skipper butterfly Carterocephalus palaemon (Pallas)
This study investigated the ecology of the chequered skipper butterfly Carterocephalus palaemon (Pallas) and was designed to reveal aspects particularly relevant to its conservation. C.palaemon is a rare species confined to a small area on the west coast of Scotland and was once common in central England. It was one of only four butterflies given full legal protection in the Wildlife and Countryside Act of 1981 and thus has a high conservation priority. The study was funded by the nature Conservancy Council. C.palaemon occurs at specific sites throughout its range but, in contrast with other butterflies that occupy precise habitats, does not exhibit colonial characteristics i.e. it exists at low density and has an open population structure with a high degree of dispersal of adults from the flight area. This may be attributable to the abundant semi-natural resources in the region, posing few barriers to movement. It is a butterfly of woodland edge and scrub habitats but adults make use of other areas, such as wet meadows. Features important to adults are shelter, abundant nectar sources for females and areas that provide favourable conditions for mate location by males. Larvae also occur at low density but in different situations to adults. Although some are found within the obvious flight areas, many more probably occur elsewhere, indicating the large area of habitat C.palaemon requires. They have a long development period, in excess of four months, and the availability of the foodplant, Molinia caerulea Moench, in good condition at the end of the year is critical to survival. M.caerulea is common and widespread in Scotland but the majority of this becomes unsuitable for feeding before larvae have completed development. Only where it grows in areas with a favourable water supply and soil relations, usually with soil-enriching plants, that enhance the quality of M.caerulea and prolong its season, can larvae survive. Hence, it is proposed that the length of season available to larvae is important and success may also be determined by the timing of the adult flight period, which is already early in the year.