Butterflies of
Britain & Europe
Large Heath
Coenonympha tullia
MULLER, 1764
Family - NYMPHALIDAE
subfamily -
SATYRINAE
Tribe - SATYRINI
subtribe - COENONYMPHINA
introduction
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habitats |
lifecycle |
adult behaviour
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Coenonympha tullia tullia, form
davus, Whixall Moss, Shropshire, England |
Introduction
The
Large Heath is distributed across much of Europe, occurring in northern
Britain, Scandinavia, north-east France, Germany, and eastwards across temperate
Asia to Amurland. It also occurs across much of North America from Alaska to
California in the west, to Newfoundland in the east.
There are several forms of the butterfly in Britain -
polydama,
found in north-east England, south-east Scotland, Wales and Northern Ireland;
davus,
found in Shropshire and north-west England; and
scotica,
from northern and western Scotland. The latter may possibly represent a valid
sub-species, but the presence of transitional forms elsewhere in the butterfly's
British distribution range suggests that the species forms a cline, and that sub-species designations are
invalid.
Most examples
of davus from Shropshire and Cumbria tend to be
brightly coloured and have very prominent ocelli on the
underside wings, while scotica
are virtually
devoid of ocelli, and resemble over-sized Small Heaths. The most widespread form
polydama is intermediate between the two.
It has been suggested by Mellor that
the evolution or adaptation of these various forms or races is climate-related :
Butterflies in the colder northern regions tend to be less active, even in sunny
weather, and probably benefit from the camouflage afforded by their plainer
undersides. Those at warmer sites further south however spend more time in
flight and are likely to attract the attention of birds. Thus they may have
developed ocelli on the outer wings to deflect bird attacks away from their
bodies. Natural selection would therefore favour the retention or development of
ocelli in southern populations.
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Historically the
Large Heath has been known by several alternative names
including Scarce Heath, July Ringlet, Silver-bordered
Ringlet, Marsh Ringlet, Small Ringlet, Manchester Argus and
Gatekeeper - the latter name now being in common usage for
Pyronia tithonus, which has
also had several previous English names including Hedge
Brown, Hedge Eye, Small Meadow Brown, and Large Heath. Thus
the names Gatekeeper and Large Heath have at certain times
in the past been interchangeable ! |
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Coenonympha tullia "scotica", Isle of Skye,
Scotland |
Habitats
In mainland Britain the
Large Heath
is found on boggy moors, peat mosses and raised blanket bogs. Most colonies are
at low altitudes, and are characterised by the
presence of scattered birch, pine, bilberry,
bog myrtle, willow, and extensive flushes of the larval foodplant - hare's tail cotton grass.
In the Scottish Highlands
and Tayside the butterfly is often found on areas of flat boggy ground at
altitudes as high as 760m. It is
also found on Skye and most other Scottish islands, including the Outer Hebrides - desolate
windswept lowlands, totally devoid of natural tree cover.
Large Heaths are highly sedentary in
behaviour, rarely if ever moving beyond the bounds of the bog or moor where they
emerge. They can form large colonies with populations of several thousand, but
many sites have been drained and partially converted to farmland, leaving many
colonies small and isolated, with rapidly diminishing populations.
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Coenonympha tullia tullia, form
davus, Whixall Moss, Shropshire, England |
Lifecycle
In Britain there is a single
generation of adults, emerging in late June or early July on
lowland bogs in England, and about 3-4 weeks later on high
altitude sites and in northern Scotland. In sub-arctic regions
of Canada, Alaska and Eurasia it can take 2 years to complete the
lifecycle.
The
flight season is short, and the butterflies are short-lived - the average
lifespan being only about 3 or 4 days as a result of heavy
predation by meadow pipits and other birds.
The egg, which is
straw coloured and spherical with a flattened top, is laid
singly on the stems or blades of hare's tail
Eriophorum vaginatum, white-beaked sedge Rhynchospora alba,
or more rarely on purple moor grass
Molina caerulea.
The eggs hatch after about 2 weeks.
The caterpillars hatch in late
July, and feed diurnally until the cold nights of autumn
induce them to enter hibernation. In the extreme north of their
range they hibernate when very small, while further south they
normally enter hibernation in the 2nd or 3rd instar. In the
spring, after awakening from hibernation they often feed
diurnally, and can be found at rest on the upper part of the
stems of sedges.
The fully grown larva is green,
with a dark green dorsal stripe, and a pair of white lines along
each side. The head is green, and the anal prongs, used for
ejecting faecal pellets, are pink.
The chrysalis is bright green,
with blackish stripes in the wing cases, and hangs by the
cremaster from the stems of grasses, sedges or shrubs. The pupal
stage lasts for about 3 weeks.
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Coenonympha tullia tullia, form
davus, Whixall Moss, Shropshire, England |
Adult behaviour
Large Heaths often rest
for long periods, typically settling on mosses or amidst tussocks of grasses or sedges.
They often bask amongst leaf litter or on patches of bare peat
soil,
with wings closed and tilted over to one side. They have a gentle
bobbing flight, and are reluctant to settle while the sun shines,
but dive into the grasses as soon as the sun is obscured by cloud.
When at rest in the grasses the butterflies are easily disturbed,
even in weather conditions which would prevent other species from
flying : to obtain the photographs on this page I had to
drive for 4 hours to reach Whixall Moss, with the weather
deteriorating rapidly as I headed northwards. By the time I
arrived it was heavily overcast, and gale force winds were ripping
off tree branches which littered the roads along the route. Having
travelled so far I was determined to find a butterfly or two
however, and set out across the moor, barely able to stand upright
in the face of the wind. Even in these conditions the occasional
Large Heath would fly up as I staggered along the tracks across
the site. Most were instantly grabbed by the wind and blown a
hundred metres across the wet boggy terrain, but two landed within
sight, settling on the ground in sheltered hollows. I later found
a third individual at rest on bell heather, where it was sheltered
by a belt of oak woodland.
At
Meathop Moss in Cumbria, and Moss of Achnacree in Strathclyde,
I've watched the butterfly in more pleasant weather conditions !
The terrain at these and most other sites is very waterlogged.
Chasing after butterflies is a risky business - much of the
habitat appears to be safe to walk on but this is very misleading,
as what seems to be dry ground can suddenly give way beneath your
feet, and you can find yourself waist deep in a quicksand-like
bog. The safest way to operate therefore is to stay on dry tracks,
or very carefully walk on the higher ground, testing it with your
feet as you go. Once stationed in a suitable spot butterflies will
occasionally settle close enough for detailed study or
photography. If disturbed
they
can fly very rapidly, covering distances of up to 200 metres before
settling again, so it is pointless and dangerous trying to chase
after them.
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Coenonympha tullia tullia, form
davus, Whixall Moss, Shropshire, England |
At Meathop I have seen the butterflies nectaring at cross-leaved
heath, bramble and bell heather. They probably also nectar at
marsh lousewort, and at orchids, both of which are profuse at many
of their sites. At Meathop, Achnacree and Skye I have also
observed males imbibing moisture from damp peaty soil.
I
have not observed courtship behaviour in this species, and can
find no reference to it in literature, but it is likely to be
similar to that of the closely related Small Heath. I have however
on several occasions found copulated pairs in the late morning. Copulation lasts for at
least half an hour, often longer, and while copulated the
pair take to the wing if disturbed, with the male carrying the female in
flight.
Overnight or
during spells of inclement weather the butterflies ordinarily roost deep amongst grass tussocks,
but I have also found them clinging to twigs of
birch saplings or bog myrtle bushes.
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