The Scales of Butterfly Wings

摘要

Butterflies are a part of the large and success-ful order of insects - the Lepidoptera or scalew-ings. Of the approximately 165,000 species of Lepidoptera about 20,000 are butterflies, rep-resenting five families (although in the past the number of families recognised was somewhat larger). There are fewer than 60 British species of butterflies but they do form an important part of our natural world, although some are becoming increasingly rare. At one time it could be said that the small tortoiseshell (Aglais urticae) was one of our most common garden butterflies but it vanished from our own garden in Shalford, Surrey for two years and, in 2009, only a sin- gle specimen was seen. The parasitic fly Sturma bella may be largely to blame but it is possibly not the only agent caus-ing this loss. Sturma bella was first recorded in the UK in 1998 and lays its eggs on nettles which are the food plant of small tortoiseshell caterpillars. The eggs are eaten by the caterpillars, hatch inside their bodies and continue to develop eventually killing the caterpillar or chrysalis. Dr Sofia Gripenberg is leading a programme of research into the plight of the small tortoiseshell at Oxford University.