Great British Lepidoptera

British Swallowtail

(Papilio Machaon ssp. britannicus)

These lovely butterflies survive in Britain as fragile populations in a man-made habitat; the Norfolk Broads, which were excavated for peat during the Middle Ages. They are entirely dependent on the caterpillar's foodplant; Milk Parsley, which varies in its numbers each year.

The Swallowtail was much more widespread in the past, occuring throughout the fens of East Anglia and probably in the marshes of of the Thames and Lea Rivers. It became extinct in the Wicken Sedge Fen in Cambridgeshire in the early 1950's, and an attempt in 1975 to reintroduce it. Conservationists planted 3,500 Milk Parsley plants are released 228 butterflies, but the drought of 1976 followed and the attempt failed. The butterfly is now protected by the Widlife and Countryside Act of 1981.

Visitors to the broads may see Swallowtails from late May to mid-July. Each butterfly lives a month, but its chance of reaching the butterfly stage is small because of high losses of caterpillars and chrysalises to spiders, birds and small mammals. Land drainage was responsible for the Swallowtail's disappearance in the past. Maintenence of high water levels and preservation of milk parsley are necessary for its survival in the future.