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Butterflies of
Britain & Europe
Swallowtail
Papilio machaon
LINNAEUS, 1758
Family -
PAPILIONIDAE
subfamily -
PAPILIONINAE
Tribe - PAPILIONINI
introduction
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habitats |
lifecycle |
adult behaviour
Text and photographs protected by Copyright © Adrian
Hoskins 2007-2008, and must not be reproduced or published in part
or in whole elsewhere in any form without written permission from
Adrian Hoskins. Breach of copyright will be pursued by litigation.
Website designed, produced and owned by
Adrian Hoskins
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.
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