The swallowtail is Britain's largest butterfly and also one of its most beautiful.

Statistics
Wingspan: up to about 80mm.

Physical description
Swallowtails are a large yellow butterfly covered in a pattern of black marks and veins. The lower wings have a curved band of blue ending in a small red spot. It has distinctive long black tails projecting to the rear.

Caterpillars are black and white at first, and look like bird droppings to fool potential predators. When they are larger, they turn green with black and orange rings and have retractable 'horns' on their heads which produce a foul smell in order to deter predators.

Distribution
They are widespread in mainland Europe, but are restricted to the Norfolk Broads in Britain.

Habitat
They inhabit marshland.

Diet
In Britain the caterpillars feed only on milk parsley.

Reproduction
The eggs are laid singly on the food plant. These butterflies usually produce two to three broods from April to September. When broods hatch out in the same year the crysalids are usually green, but when they overwinter as pupae they are usually brown.

Conservation status
Swallowtails are confined to the marshes around the Norfolk Broads but they used to be common throughout the fens of East Anglia. Many marsh areas are now managed specifically for this species, and numbers are again increasing. They are not listed as endangered on IUCN Red List 2000.

Records
Swallowtails are the largest British butterfly.