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Text and photographs protected by Copyright © Adrian Hoskins 2007, and must not be published in part or in whole elsewhere without prior written permission from the author.
Butterflies of Britain & Europe
 
Swallowtail
Papilio machaon LINNAEUS, 1758
Family - PAPILIONIDAE
subfamily - PAPILIONINAE
Tribe - PAPILIONINI
 
 introduction | habitats | lifecycle | adult behaviour
 
Papilio machaon gorganus, St Germain l'Herm, Auvergne, France
 
Introduction
 
The Swallowtail is a widespread and common species throughout much of the northern hemisphere. It occurs over the whole of continental Europe, eastward across temperate Asia to Japan; in Africa north of the Sahara; and throughout much of North America.
 
There are no similar species occurring in Britain. On the Mediterranean islands of Corsica and Sardinia it shares it's habitat with Papilio hospiton, which is similarly marked but has much shorter tails on the hindwings. In Algeria the distribution of machaon overlaps that of the Saharan Swallowtail Papilio saharae, which is identical in appearance except for the antennae, which have 30 segments in saharae, and 33-36 segments in machaon.
 
Papilio machaon gorganus, Mont Dore, France
 
Habitats
 
Throughout most of it's range the Swallowtail shows itself to be highly adaptable, utilising a wide variety of habitats including sub-arctic tundra in Canada, prairies, woodlands and arid canyons in the south of the USA; hay meadows, roadside verges, river banks and sub-alpine pastures in Europe; high montane habitats in the Atlas mountains of north Africa, and semi-cultivated habitats in the Mediterranean area.
 
It's adaptability extends also to it's choice of larval foodplants - in North America the caterpillars invariably feed on Compositae ( Artimesia, Petasites ), while in Europe Rutaceae  ( Ruta, Haplophyllum ) and Umbelliferae ( Foeniculum, Peucidanum etc  ) are used instead. In Britain however the butterfly is restricted to a single foodplant - milk parsley, and breeds only at a very small number of wet fenland habitats in north-east Norfolk.
 
Several centuries ago the species almost certainly occurred as a resident species over a much wider area of southern and eastern England, but later contracted it's range to the Great Fen - a vast area of wetlands covering Cambridgeshire, Lincolnshire and Norfolk. Following the drainage of this area, and it's conversion to agriculture, the butterfly was forced to contract it's range even further - to the Norfolk Broads. In such isolation the genetic diversity would have diminished, causing the so-called "sub-species" machaon brittanicus to become far less adaptable, and to acquire minor differences in appearance from the ancestral stock.
 
In the last 100 years the average wingspan of Swallowtails, and the average width of the thorax, have reduced in size, an indicator of further genetic impoverishment, which is likely to result in further contraction and eventual extinction. Expansion of the gene pool can only be accomplished by the introduction of genetically richer livestock from Europe, a policy which hopefully will eventually be adopted by conservation groups.
 
Although the butterfly only breeds in the wet fenlands of Norfolk, migrants from France are periodically observed at coastal sites in Dorset, Hampshire, the Isle of Wight, Sussex and Kent. On 1st Sept 2003 for example I watched an immigrant Swallowtail flying across a main road at Milford-on-Sea in Hampshire. In most years less than half a dozen are recorded, usually in August or September. Individuals very occasionally penetrate further inland, and are reputed to sometimes breed on chalk grasslands, feeding as larvae on wild carrot Daucus carota, although I know of no recent records.
 
Papilio machaon gorganus, Loire valley, France
 
Lifecycle
 
The butterfly is bivoltine on the continent, emerging in May and August, but in Britain the second brood is either partial or non-existent.
 
In the Norfolk fens, the butterflies emerge in late May and early June, when they lay their large brown globular eggs, singly, on the fine leaves of milk parsley Peucidanum palustre ( also known as hog's fennel ). The eggs are nearly always laid on the upper foliage of tall specimens which project above the surrounding reedbeds. They hatch after about a week.
 
The young caterpillar is black, marked with a band of white, and looks remarkably like a small bird-dropping as it rests openly on the leaves. When fully grown in July, it is a most magnificent creature - bright green, marked with narrow black bands and orange spots. Behind it's head is an eversible fleshy pink forked structure called an osmaterium, which is raised if the larva is irritated. This structure emits pungent chemicals, capable of deterring ants, wasps, and flies.
 
The chrysalis occurs in 2 colour forms, being either plain green, or light brown with a dark lateral stripe. It is attached vertically by a thin silken girdle and by the cremaster, usually low down on the stem of a reed, where it hibernates until the following May.
 
Papilio machaon gorganus, Loire valley, France
 
Adult behaviour

 

The butterfly has a characteristic powerful gliding flight, and is capable of covering large distances. In France and Spain for example I have often observed males indulging in "hill-topping", i.e. flying to congregate at the top of hills, where they compete for the attention of passing females. In Britain however the butterfly breeds only on the flat terrain of Norfolk, and probably only covers short distances, although it can be seen crossing open expanses of water on the Broads.

 

On warm sunny days Swallowtails patrol back and forth along a regular route, fluttering their wings constantly as they nectar at the pink flowers of angelica, knapweeds, marsh thistles, red campion, ragged robin and valerian. This fluttering behaviour is typical of all Papilioninae, wherever they occur in the world.

 

Early in the day, or during hazy sunshine, the butterflies can sometimes be seen basking amongst dry grasses. During overcast weather they roost hanging from reed stems, and probably also amongst the foliage of sallow bushes and other fenland vegetation.

 

In the French Alps and the Pyrenees the butterflies commonly indulge in mud-puddling - siphoning mineral-rich moisture from damp mud and cattle dung, but I have not observed this behaviour in Britain.

 
                                                       
Almost every British and European species of butterfly is declining rapidly in numbers, due in most cases to loss or degradation of habitats.
 
You can help to reverse the decline by supporting conservation organisations which purchase and manage habitats as nature reserves, and which lobby government at local, national and international levels, often very successfully, to bring about changes in farming, forestry and urban development policies.
 
Please contact the conservation organisations for advice on how you can help protect British and European butterflies and their habitats. You may be able to offer practical help e.g. by monitoring butterfly populations or helping to manage nature reserves. Donations to these organisations enable them to employ ecologists and biologists. Even if you are unable to provide such help, merely having your name on the membership list can be a powerful tool for conservation organisations wishing to demonstrate the levels of support they have for their policies.

 

 
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