Butterflies of Britain
Family - PAPILIONIDAE
Tribe - PAPILIONINI
Papilio machaon gorganus, St Germain l'Herm, Auvergne, France ©
Back in the 18th
century when Linnaeus created the System Naturae, the word
Papilio was used as the genus name for
every known species of butterfly in the world. Since then much has
been learnt about the relationships between different species.
Consequently most have been reassigned to new genera, and only about
215 of the 17600 currently known species are retained in
is widespread and common 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. In Britain it is locally common on
the Norfolk Broads, an area of fenland and lakes in eastern England.
Individuals originating from France occasionally migrate across the
English Channel and have been periodically recorded in Hampshire,
Dorset, Sussex and the Isle of Wight, but such sightings are very
rare - perhaps one or two sightings per year. Genuine migrants can
usually be recognised by their faded and worn appearance.
Fresh looking insects seen anywhere apart from Norfolk can be
attributed to escaped or deliberately released livestock - both the
British subspecies brittanicus and the
continental gorganus are commonly
reared by hobbyists. ( it is illegal to capture or breed stock of
British origin, but nevertheless a widespread practice ).
There are no similar species occurring in
Britain. On the Mediterranean islands of Corsica and Sardinia
machaon 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, female, Mont Dore, France ©
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
extends also to it's choice of foodplants - in North America the
caterpillars usually feed on Compositae (
Artimesia, Petasites ), while in
Europe Rutaceae ( Ruta,
Haplophyllum ) and Umbelliferae (
Peucidanum etc ) are used instead.
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. Individual specimens have been
tagged and found to fly over quite a large area, often reaching
adjacent fens, but the butterflies do not stray beyond the general
area of the broads.
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.
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 and broads 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, reportedly feeding as larvae on wild
carrot Daucus carota, although I know
of no recent records.
It is planned that by
the end of the 21st century the Great Fens which formerly occupied
much of eastern England will be partially restored, leading to a
sizeable increase in suitable habitat. Whether such a project is
feasible in the face of population expansion however remains to be
Papilio machaon gorganus, Loire valley, France ©
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
where the butterflies emerge in late May, they lay their large brown
globular eggs singly on the fine leaves of milk parsley
The eggs are nearly always laid on the upper foliage of tall plants
which project above the surrounding reedbeds. They hatch after about
The young caterpillar is
black, marked with a band of white. It looks remarkably like a small
bird-dropping as it rests openly on the leaves. According to Thomas
the camouflage is not effective against spiders, which may predate
up to 65% of 1st instar larvae. When fully grown in July, the
caterpillar 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, but does not
deter birds - reed buntings, sedge warblers and bearded tits between
them devouring at least 50% of mature larvae.
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 ©
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 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,
male Swallowtails patrol back and forth along a regular route in
search of females. Often both sexes home in on a particular clump of
bushes where courtship and copulation take place. The pair often
remain joined for 2 or 3 hours before the female departs to oviposit.
morning, and again in late afternoon both sexes can be seen flying
freely about their habitat, pausing regularly to nectar at
the pink flowers of angelica, knapweeds, marsh thistles, red campion,
ragged robin and valerian. When nectaring they keep their wings
constantly fluttering to prevent the weight of their bodies from
dragging down on the fragile flowers. This fluttering behaviour is
typical of all Papilioninae, wherever they occur in the world. In
Norfolk the butterflies also often nectar at the spectacular bright
yellow flowers of yellow iris.
but sunny weather, or during periods of hazy sunshine, Swallowtails
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 and alder bushes, and other fenland vegetation.
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.
Papilio machaon, River Bure, Norfolk ©