THE ECOLOGY OF THE CHEQUERED SKIPPER BUTTERFLY CARTEROCEPHALUS PALAEMON IN SCOTLAND .2. FOODPLANT QUALITY AND POPULATION RANGE

1. The growth form and nutrient content of the foodplant of the butterfly C. palaemon, purple moor-grass Molinia caerulea, were compared in areas where larvae survived to hibernation and where they failed to develop, corresponding to the known distribution of microhabitats in which larvae were found and rarely occurred. Larvae tended to occur on foodplants of richer soils, such as flushes, in association with soil-enriching plants, and not in nutrient-poor conditions. 2. Larvae had a long development period from hatching in late June to hibernation in fate October or early November. Plants on which larvae survived had a larger growth form, fewer flowers, persisted longer and had higher nitrogen concentrations. 3. Larvae fed on only leaf blades with the highest nitrogen concentrations and, overall, plants in larval microhabitats were of higher nutrient status. 4. The differences in nitrogen concentrations were particularly pronounced towards the end of the larval season and plants in larval microhabitats remained green whilst plants in other areas were already senescent. 5. The longevity and enhanced condition of the foodplant in larval microhabitats are proposed as factors limiting the range of C. palaemon. The area the butterfly inhabits is shown to have a mild and wet climate with a long growing season. The species may be prevented from colonizing habitats to the south and west by a pronounced change in geology and topography, which may adversely affect the development and drainage of soils important in producing foodplants of enhanced nutrient status.