Butterflies of Britain
Family - NYMPHALIDAE
subfamily - SATYRINAE
Tribe - SATYRINI
subtribe - PARARGINA
Lasiommata megera, male, Dorset ©
There are 16
Lasiommata species distributed
variously across Europe and temperate Asia. Some workers classify
Lasiommata as a subgenus of
Pararge, which comprises of a further 3
The Wall Brown is found
across most of Europe with the exception of northern Britain and
northern Scandinavia. It also occurs over much of north Africa, and
in temperate regions of western and central Asia.
and Wales the Wall Brown was formerly more widespread, and occurred
in a wide range of habitats. In the latter part of the 20th century
it became evident that most of the inland colonies were dying out,
and the species was contracting it's range westward, and towards
current time ( 2008 ) the species is restricted largely to sites
within about 10-15 miles of the coastline, and is most frequently
encountered at coastal habitats : cliff-tops, undercliffs,
south-facing grassy slopes, shingle banks, sea walls and sand dunes.
There is some
evidence that the butterfly is beginning to regain lost ground,
recolonising inland sites e.g. in Dorset, Wiltshire, and in the
north of England. The most northerly colonies occur around the coast
of southern Scotland.
The reasons for the collapse of inland colonies, and the recent
slight recovery, are probably related to climatic changes. The
butterfly seems to thrive best when cold and harsh winters are
followed by warm dry summers, and to collapse when winters are mild
and wet. It clearly needs conditions to be warm and sunny during the
flight periods, and even if there is enough warmth for eggs to be
laid in reasonable numbers a few days of rain can easily cause them
to be washed away. Over 8 months of the lifecycle are spent in the
caterpillar stage, and if conditions are mild and wet between
September and April, as they have been in recent years, the larvae
are more prone to viral attack; and exposed for an extended period
to predation and parasitism.
Lasiommata megera, male, Arnside Knott,
All habitats are
characterised by having extensive areas of exposed ground in the
form of well trodden paths, eroding banks, scree, rabbit scrapes
Colonies tend to be
small, comprising no more than about 20 or 30 individuals on the
peak day of the flight season, even at the best sites.
Lasiommata megera, male, Dorset ©
butterflies are double-brooded, the first generation emerging in
late April and early May, and the second generation in late July or
early August. In exceptionally long and warm summers there may be a
partial third brood emerging in October.
pale greenish-white eggs are laid singly or in clusters of 3 or 4,
on the roots of grasses where they overhang into sunny recesses at
the edge of eroded ground. Rabbit scrapes, path edges, and crumbling
undercliffs are typical situations. I have also seen females laying
on grass blades at the base of gorse and bramble bushes on
south-facing chalk grassland slopes. The eggs hatch after about 12
The caterpillars feed nocturnally on various
grasses including Agrostis tenuis,
Agrostis gigantea, Brachypodium
sylvaticum, Brachypodium pinnatum, Dactylis glomerata, Deschampsia
flexuosa and Holcus lanatus.
Summer brood larvae hatch in August and enter hibernation while
still quite small. In late February they re-awaken, becoming full
grown by late March or early April. The mature larva is pale
bluish-green, with whitish stripes along the back and sides.
pupa is virtually impossible to locate in the wild, and varies in
colour from pale green to deep olive and sometimes almost blackish.
It has reportedly been found hanging from grass stems around the
base of small bushes. The pupal stage lasts for about 2 weeks.
brood Wall Brown, male, Ouse Estuary, East Sussex ©
calm days the butterflies tend to inhabit cliff tops and other high
ground, but when it is cooler or windy they seek shelter and warmth at
the bottom of hills. They tend to
spend long periods settled on bare ground on paths, rabbit scrapes or
overhangs. In lightly overcast weather, or during cooler conditions
cool early or late in the day, males bask with wings outspread,
exposing the maximum wing area to the sun. Another tactic they use is
to raise the wings to a 45° angle, which traps pockets of warm air
above the thorax and abdomen. These thermoregulatory actions are
essential, enabling them to achieve the high body temperatures vital
for rapid take-off and interception of potential mates. They
intercept all passing butterflies of roughly similar size and colour,
including Peacocks, which they chase away from their territories.
Smaller butterflies, and those with much brighter colouring such as
Orange tips, Large Whites, Clouded Yellows and Brimstones are ignored.
When a male intercepts
a female, a short but elaborate courtship ritual takes place, in which
the male chases the female until she settles on the ground, and then
flies around her, eventually settling in front of her, face to face.
The female then responds by quivering her open wings, at which point
the male half opens his own wings, and "bows" several times to his
Lasiommata megera, courtship ritual ( male on left ), Alner's
Gorse, Dorset ©
In hot conditions Wall Browns close
their wings immediately on landing, with the fore-wings raised so that
the apical ocellus is visible. This probably acts as a decoy, so that
any bird which spots where the butterfly has settled, attacks the
false-eye marking, rather than the butterfly's body. After a moment,
when the butterfly is sure it has not been followed, it lowers the
forewing to hide the ocellus. This behaviour is common to several
other Satyrines including Grayling, Small Heath and Meadow Brown.
Wall browns are at all times
extremely alert, and are notoriously difficult to approach. Even in
cool conditions they react instantly to the slightest disturbance,
rapidly flying up and disappearing over the top of tall bushes. The
high energy levels of males cause them to "burn themselves out" very
quickly, and thus they are one of the shortest lived British species,
with an adult lifespan of only 3 or 4 days. Females, being more
sedentary, live longer, averaging about 8-10 days.
The butterflies are
notoriously difficult to photograph - I’m well used to playing hide
and seek with them - clambering up slopes,
peeking over tussocks of grass at basking males, hoping I can press
the shutter release before they detect me.
It takes more than careful stalking to get the better of a Wall Brown
day in May 2008, I spent over 4 hours attempting to photograph various
individuals, but each time, although the butterfly was static and
composed nicely in the centre of the viewfinder, by the time the
shutter had fired it had flown. I took over 20 photographs, but in 18
of them the butterfly was absent from the final image, or caught in
flight at the edge of the frame.
Incredible as it seems, Wall Browns are able
to detect the sound of the SLR mirror as it flips up, and shoot
into flight before the
shutter opens. The delay between
mirror-up and shutter release is just a few
milliseconds, but in that time the butterflies can not only detect the
sound and register it as a threat,
but can trigger an escape response
and take flight, becoming nothing more than
a blur at the edge of the image, or leaving the photographer
with a photograph of a patch of vacant soil.
Both sexes patrol back and forth
along a regular route, often along paths or areas of broken ground,
high on hillsides or cliff tops. They go through a regular cycle of
patrolling, resting and nectaring.
Favoured nectar sources include
buttercups, dandelions and common vetch in spring, while in summer
they favour scabious, hawkbit and hemp agrimony.