The vegetation of the habitat of the Brenton blue butterfly, Orachrysops niobe (Trimen), in the Western Cape, South Africa

THE BRENTON BLUE BUTTERFLY IS KNOWN only from a small population in one hectare of asteraceous coastal fynbos at Brenton-on-Sea. This fynbos is characterized by a great diversity of shrubs, herbs and graminoids, with a successional gradient to thicket where Pterocelastrus tricuspidatus is dominant. The eggs of the butterfly are laid on the lower side of the leaves of Indigofera erecta, on which the larvae feed. Fifteen 1-m2 quadrats containing plants of Indigofera erecta with and without eggs of the butterfly were distinguished and sampled separately from 15 1-m2 quadrats containing plants of Indigofera erecta without eggs. No marked differences in total vegetation, shrub or herb cover between the sites with and without eggs were observed. There was a difference in abundance of the fern Pteridium aquilinum, with over 30% cover at sites with no eggs and only about 6% at sites with eggs present. This could reflect the absence of other plants where the ferns had such dense cover.