Butterflies of Britain
Family - NYMPHALIDAE
subfamily - SATYRINAE
Tribe - SATYRINI
© Neil Hulme
Mountain Ringlet was almost certainly the first species to arrive in
Britain as the last "mini Ice Age" ended 10,000 years ago, and at
that time probably occurred across much of southern England. As the
ice retreated the butterfly would have been forced to move to cooler
regions in the north, and ultimately to seek refuge on the high
mountains where it still breeds today.
distribution within Britain is now very limited, it
still widespread across Europe, but restricted to mountainous
regions where it occurs at altitudes above 900m in the Vosges and
Massif Central, and above 1200m in the Alps, Pyrenees, Picos de
Europa, Tatra Mountains, Carpathians and other ranges.
There are no similar species in the British
Isles, but in Europe there are no less than 46 members of the genus
Erebia, and among these are several
which could be confused with epiphron,
and which share similar habitats. The use of a good field guide is
therefore essential for identification.
the Mountain Ringlet occurs in small isolated colonies, typically at
altitudes between 450-800m although in parts of it's range it can be
found as low as 100m, and it occurs as high as 1000m. In Scotland
the butterfly is found in the Grampians from Ben Nevis in the west
to Glen Clova in the east. The most well known and accessible
colonies are at Ben Lawers, and in the mountains above Tyndrum. In
England the species occurs in the Lake District ( at Langdale
Pikes, Stye Head Tarn, Red Screes, Helvellyn and elsewhere ), but it
is absent from the Pennines and from Snowdonia.
At the peak of the
flight season as many as 3000 adults may be on the wing at certain
sites, but these high numbers tend to be concentrated within a very
limited area, sometimes less than half a hectare in area. The
butterflies breed in sheltered damp depressions where the larval
foodplant mat grass thickly carpets the ground. These habitats are
usually extremely localised, forming a small element within a
montane landscape of scree slopes, tarns ( large shallow ponds ) and
areas of flat or slightly undulating grassland.
The flight period varies considerably according
to elevation and seasonal weather conditions. In a warm summer
populations at low altitudes in the Lake District can begin to
emerge as early as mid June. At the other extreme, colonies at high
altitudes in the Grampian mountains may be delayed until early July
in a "late" season. The flight period at individual sites is very
short - probably less than 3 weeks between the appearance of the
first males, and the disappearance of the last females.
The butterflies lay
their eggs singly at the base of blades of mat grass
After consuming its eggshell, the newly hatched caterpillar feeds
solely on mat grass. In September when in its 2nd instar it enters
hibernation, spending the winter deep at the base of the grasses,
and may be buried under snow for several months. In the spring,
after the snows melt, it awakens and resumes feeding, becoming fully
grown by early May. Like most Satyrine larvae it feeds nocturnally.
It feeds high up on the grass blades, leaving nibbled notches which
give away it's presence. In poor spring seasons larval development
may be very slow, and at some sites it is probable that some of the
caterpillars are unable to complete their growth in a single season,
and may spend 2 successive winters in hibernation.
chrysalis is pale green, with brown striations on the wing cases. It
is formed within a very flimsy cocoon - little more than a few
strands of silk - at the base of grass tussocks.
areas where the butterflies breed often have large populations of
voles living nearby, causing one writer to speculate "it is believed
that huge numbers ( of pupae ) are killed by the short-tailed voles
that teem among the loose scree found alongside most Mountain
Ringlet sites". This however is erroneous, as short-tailed voles are
entirely vegetarian, unlike their relative the bank vole which eats
insects as well as vegetation.
During cool or cloudy
weather the butterflies hide deep amongst grass tussocks and are
virtually impossible to find. Even walking through the middle of their
breeding sites at such times usually fails to disturb the butterflies
from their deep torpor. The appearance of sunshine however - even for
a brief period, quickly arouses them, causing the entire colony to fly
have a very weak fluttering flight just above the grasses. Males
patrol back and forth while the sun shines, dipping down at intervals
into the grasses to investigate any dark object that could potentially
be a female. Females rest in grass clumps prior to mating, which takes
place with little evidence of pre-nuptial ritual. After about an hour
( much longer if cloud cover returns ) the sexes separate, and the
female rests for a day before beginning to lay her eggs.
not observed this species nectaring at flowers, either in Britain or
continental Europe, even though plants including
Cerastium may be flowering in it's habitat. My own observations
of adult feeding, both in Britain and the French / Swiss Alps, have
been limited to finding males imbibing dissolved minerals from damp
peaty soil or from rocky ground at the edge of tarns or streams.
They are nevertheless
known to nectar at Tormentil, and are
also reputed to nectar at Thymus.
Erebia epiphron nectaring at Tormentil,
Red Tarn, Great Langdale, Cumbria
© Nigel Kemp