Butterflies of
Britain & Europe
Small Heath
Coenonympha
pamphilus
LINNAEUS, 1758
Family - NYMPHALIDAE
subfamily -
SATYRINAE
Tribe - SATYRINI
subtribe - COENONYMPHINA
introduction
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habitats |
lifecycle |
adult behaviour
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Small
Heath
Coenonympha pamphilus, Heyshott Down,
Sussex |
Introduction
This is one of the most
widely distributed species in the Palaearctic region, being found throughout
most
of Europe, including most of the Scottish islands, most of the Mediterranean islands, and east
across temperate Asia to Mongolia. It is also widespread across most of north-west Africa.
Prior to the 18th century the male Small Heath was called the Selvedged
Heath Eye, and the female was known as the Golden Heath Eye. These names refer
to the small but prominent ocellus at the apex of the forewing. Later it was
realised that both "Heath Eyes" were the same species, which became known as the Gatekeeper,
although that name is now associated with a different species -
Pyronia tithonus.
The name Small Heath was proposed by the famous 18th century entomologist Moses
Harris, in his book "The Aurelian".
In
continental Europe there are several other similar
Coenonympha
species, but all of these have prominent ocelli on the underside hindwings. In
Britain the only species with which
pamphilus
can be confused is the Scottish race of the Large Heath C. tullia,
which has almost identical markings, but is much larger in size.
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Small Heath
Coenonympha pamphilus
in typical
resting / basking posture amongst grasses |
Habitats
Despite it's common name,
this is not primarily a heathland species, although populations do occur on the
heaths of the New Forest and elsewhere. It is in fact found across a wider range
of habitats than any other British butterfly - occuring on open grassland,
mountainsides, road embankments, old quarries, cliff tops, sand dunes, heaths,
moorlands, meadows and around field margins. It also occurs
sparingly in woodland where it can be found in clearings and along wide grassy
avenues.
It
is most abundant at warm, well-drained, south-facing sites which are lightly
grazed to produce a sparse sward of fine grasses. At such sites populations can
sometimes be enormous, although they fluctuate dramatically in response to
grazing and climate.
Lifecycle
In most areas of Britain
the butterfly produces 2 broods, the first of which emerges as early as late
April at the warmest sites, but usually in mid May elsewhere. Most areas produce
a 2nd generation emerging in August and September, but in mountainous regions and in the
far north there may be only a single generation, emerging in June.
Emergence times vary
considerably from site to site.
Thus it is possible to see the
Small Heath on the wing at almost any time between April and October by visiting
appropriate sites.
The eggs are spherical, with reddish blotches.
The ground colour of eggs laid early in the life of each female is pale green
but older females produce slightly smaller straw-coloured eggs. They are laid singly
at the base of grass blades.
The
larva also has several colour forms, varying from pale green to reddish-brown, but
always with narrow white stripes, and tiny, twin pink and
white prongs at the tail end. It feeds openly in daylight on tufts of Festuca, Agrostis
and other fine grasses.
Some
of the first brood larvae feed up quickly to produce adults in August, but
others feed more slowly, with larvae of both broods entering hibernation in late
September, some being quite small, while others may be half grown or almost
fully developed. They
over-winter at the base of the grasses, and resume feeding in late March.
The
pretty pupa hangs by the cremaster from grass stems, and is pale green, marked on the
wing cases with black stripes.
Adult behaviour
In the spring the butterflies
nectar mainly at daisies, but the summer generation insects
visit a much wider range of flowers including small
scabious, marjoram, clover, thyme and heathers. Both broods
however only visit low growing flowers, and rarely if ever
nectar at taller plants such as knapweeds, hemp agrimony or
thistles.
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Small Heaths often settle on
stones. The heat reflected back helps the butterfly to maintain a high body temperature
and high energy levels needed for instant
flight.
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Males fly rapidly,
zig-zagging or flying in tight circles just above the grasses,
but rarely cover any distance. They frequently settle amongst
grasses or on bare ground, and are attracted to small whitish
objects such as stones, lumps of chalk, or bits of dry wood.
Second brood males often settle on the pale flower-heads
of stemless thistle or stemless carline thistle.
When the butterfly
first settles it exposes the ocellus on the
forewing apex for a moment, so that any bird which has
spotted it will aim it's beak at the
false "eye" target. After a few seconds when the butterfly feels
safe it tucks the ocellus out
of sight behind the hindwings.
The butterflies spend long
periods lateral-basking (
basking with wings closed ). By angling their wings to present
the maximum wing surface to the sun they can absorb
enough solar energy
to keep their body temperatures high. Consequently they always
have enough energy to instantly dart up and
intercept passing females, or to escape from approaching
predators. If on the other hand temperatures are high and the
butterflies need to reduce their body temperature, they tilt
towards the sun so that only the edges of the wings receive
direct sunlight.
Males are mildly
territorial - encounters with their own sex result in aerial
sorties in which the pair spiral upwards flying in tight
circles. When they reach a vertical threshold of about 3 metres
above the ground, they split up and each male returns to ground
level, although not usually to its original perch. With most territorial species, it is usual for the intruding male
to be the loser in these battles, conceding defeat to the
original "owner" of the territory. In the case of the
Small Heath however the larger of the 2 males generally drives
off the smaller, irrespective of which was the intruder.
Females fly to the
male territories, flying about to attract the attention of
potential mates. Courtship is very brief - the female settles on
the ground, and the male nudges her with his head and then
crawls alongside her, curving his abdomen to make contact. Mated pairs can
often be found
amongst grasses in late morning. If disturbed the pair will take
flight, the female carrying the smaller male to a bush or another clump
of grass. Copulation lasts about an hour.
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Small
Heath
Coenonympha pamphilus, copulated pair,
Cissbury Ring, West Sussex |
After separating the females disperse over open grassland to lay
their eggs, spending what's left of their lives walking or
fluttering about amongst the grasses inconspicuously.
As dusk approaches the butterflies migrate across their sites to
areas where there are long grasses and shelter from the wind.
There they go to roost for the night, sometimes facing
head-downwards, typically on grass-heads, plantain
flowers or dead flowerheads of marjoram.
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Small Heath
Coenonympha pamphilus, female at roost
on plantain flower |
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