The Swallowtail (Papilio machaon), is a butterfly. This beautiful species is the biggest butterfly in the British Isles, named after the protruding 'tails' on its wings, resembling that of a swallow's. However this butterfly is a rare species, and dwindled to near extinction at on period. They are protected by the Wildlife and Countryside Act of 1981, which means that they cannot be deliberately disturbed, captured or killed without risk of a fine or even imprisonment.


The imago typically has yellow wings with black vein markings, and a wingspan of 65–86 millimetres (2.6–3.4 in). The hind wings of both sexes have a pair of protruding tails which give the butterfly its common name from the resemblance to the birds of the same name. Just below each tail is a red eye spot.

Distribution and statusEdit

This butterfly is present throughout the entire Palearctic region, ranging from Russia to China and Japan, (including the Himalayas and Taiwan), and across into Alaska, Canada, and the United States.

This butterfly is widespread in Europe. In the United Kingdom it is limited to a few areas in the Norfolk Broads of East Anglia. It is the UK's largest resident butterfly.


The butterfly has a strong and fast flight, but frequently pauses to hover over flowering herbs and sip nectar. It frequents the alpine meadows and hillsides and is fond of 'hilltopping' – congregating near summits to compete for passing females. At lower elevations it can also be seen visiting gardens.

Unlike other swallowtails, this species specialises in using plants of family Umbelliferae, females laying eggs singly. Milk Parsley (Peucedanum palustre) is normally the only food plant used by the caterpillars of the British Butterflies. The food plants of the Swallowtail in Europe, Asia, and North America are more varied than in the UK. The caterpillar feeds on plants such as Rue (Ruta chalepensis) and Fennel (Foeniculum vulgare).

At lower elevations these butterflies fly from March to September. At higher elevations the butterflies are limited by the short summer seasons.

The British Butterflies are less mobile than its European continental counterpart and stays within, or close by, its fenland habitat.

Life cycleEdit

There usually are two to three broods in a year, but in northern areas the species may be univoltine. In some places such as the UK, some will pupate and emerge in the same year and others will overwinter as pupae before emerging the following year, a situation known as being partially bivoltine.

The caterpillar spends the first part of its life with the appearance of a bird dropping, an effective defense against predators. As the caterpillar grows larger it becomes green with black and orange markings. The caterpillar has a defense against predators in the form of an osmeterium which consists of retractable, fleshy projections behind its head that can release a foul smell if disturbed which deters insects but not birds.


Swallowtails can be easily bred in captivity.

Butterflies can be lured to lay eggs in a backyard garden by keeping plenty of caterpillar foodplants in it. Common Rue plants are highly appropriate for this.

Once eggs or young caterpillars have been collected, they can be kept in a pot with holes on its top to allow air circulation. More than one caterpillar may be kept in a single pot since they don't attack each other (although they might get sometimes frightened by other caterpillars moving). They can be fed any of their foodplants. Fennel is one of the most easy to find in the wild. Care must be taken with fennel, though, because they won't eat hard woody stems, they need to be fed the tender leaves. They can also be fed Rue or Milk Parsley. Feeding them with unsuitable plants will lead to death of starvation.

Caterpillars are very fast eaters, they will spend their time either eating or resting before they resume their eating again.

Once a sufficient size has been attained, they will attach themselves to any available structure with their silky threads. They will then stay still until they become a pupa. This will take about a day. They will not build a woven chrysalid, they become internally a pupa and then they shed their skin.

Once in the pupa stage, they can be very carefully removed from the pot and placed in a warm location. The time the buterfly takes to form and come out depends on the temperature. If kept in warm summer temperatures it will take about one or two weeks to form. On the other hand, if the temperature is lower, it might take as long as several months until it feels the weather is warm enough.

Pupas should not be kept on an impermeable surface, since when they eclose a bit of liquid will be poured, this means they butterfly would get wet and might not be able to fly. Absorbing paper such as the one used in kitchens is advisable.

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