Identify It > Butterfly Section > Swallowtail Butterflies >
Scientific name: Papilio machaon
Size: Wingspan approximately 95mm
Distribution: Found in the Norfolk Broads. On rare occasions migrants from the continent show up in other counties.
Months seen: May to July
Life span: Up to eight months
Habitat: Fens and marshes
Food: Nectar. The caterpillars feed on milk parsley (Peucedanum palustre)
Special features: It would be difficult to confuse Swallowtails with any other butterfly. It's one of the prettiest and certainly the largest butterfly found in the UK. The name comes from the two tail-like extensions on the hind wings.
The young caterpillars have the appearance of bird droppings to protect themselves from predators. As they get larger they become pale green with black lateral stripes and orange spots. They also have a strange appendage on top of their heads which looks like an orange coloured snakes forked tongue. It's called an 'osmeterium', and for added effect it can be flicked in and out. The caterpillar is also capable of emitting a powerful scent similar to rotting fruit.
Any Swallowtail butterflies spotted outside of the Norfolk Broads are most likely to be the continental subspecies Papilio machaon gorganus. Continental Swallowtail butterflies frequently arrive in the UK and have shown up in many of parts of England (see photo above). Their markings are slightly paler in colour, but they are larger and stronger than the British subspecies britannicus. They've been known to breed here, and the less fussy caterpillars are able to surive by feeding on plants such as hogweed, fennel and carrot.