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Swallowtail Butterfly Caterpillar

©Terry Whittaker/2020VISION

Swallowtail Butterfly

©Terry Whittaker/2020VISION

Swallowtail Butterfly

©Terry Whittaker/2020VISION

Swallowtail

Scientific name: Papilio machaon
The exotic and beautiful swallowtail is the UK's largest butterfly. A strong flier, residents can be spotted over wetlands in Norfolk during summer. Migrants occasionally appear in southern England.

Species information

Statistics

Wingspan: 7.6-9.3cm

Conservation status

Protected in the UK under the Wildlife and Countryside Act, 1981.

When to see

May to July

About

The UK's largest butterfly, the swallowtail is striking and exotic-looking. Adults fly between May and July when they can often be seen over reedbeds, or feeding on ragged-robin or flowering thistles. Swallowtails are restricted to reedbeds and marshlands in the Norfolk Broads; very rarely, migrants from the Continent appear on downland in southern England. The foodplant of the caterpillars of our native race is Milk-parsley, whereas migrants may feed on wild carrot.

How to identify

The swallowtail is a large and unmistakeable butterfly. It has creamy-yellow wings with heavy black veins and blue margins. The hindwings have distinctively long 'tails' and a red spot.

In our area

During the 20th century, especially after the Second World War, much of the swallowtail's habitat was lost. Today, active management of fenland, with reed and sedge being cut to allow other plants to grow, plays an important part in the survival of the swallowtail in Norfolk.

Swallowtails have several interesting physical features. The caterpillars have a unique forked organ behind their heads, called the osmeterium, which is normally hidden. If the caterpillar feels threatened, this organ can emit smelly secretions. The butterfly's tail resembles that of a swallow bird (which gives the swallowtail its name) and it plays an important part in the butterfly's survival by mimicking antennae. The swallowtail's two red and blue 'false eyes' also confuse predators into thinking it is a two-headed butterfly.

Best places to spot in Norfolk: Hickling Broad and Marshes; Ranworth Broad and Marshes; RSPB Strumpshaw Fen

Distribution

Native to the Norfolk Broads. Migrants may be spotted in southern England.

Habitats

Did you know?

The UK population of the swallowtail is a unique subspecies, Papilio machaon britannicus, found only here.

How people can help

The Norfolk Broads is an inland waterway and a very special area of fen, marshland and reedbed. Along with the Suffolk Broads, it is the UK's largest protected area of wetland and has National Park status. Many organisations and individuals work together within the Park to conserve and enhance its rare habitats for the benefit of both wildlife and people. Norfolk Wildlife Trust is one of these partners and has a number of nature reserves in the area which it protects for local wildlife like the wwallowtail. Become a member and support the work of your local Wildlife Trust.