Wall Brown Butterfly - Lasiommata megera

Phylum: Arthropoda - Class: Insecta - Order: Lepidoptera - Family: Nymphalidae

Wall Brown Butterfly - Lasiommata megera

This lovely 'brown' butterfly gets its common name from the habit of resting on walls with its wings open, enjoying the warmth of weak sunlight so that it is able to fly. (In very hot weather the Wall Brown seeks shade.) In practice you are even more likely to come across a Wall Brown resting on the ground, particularly on stony coastal cliff-top paths.

Wall Brown resting on a coastal footpath

Distribution

Wall Browns are found throughout England and Wales, where they are most often seen in coastal areas. Ireland's distribution of this butterfly is markedly coastal, while it is uncommon in southern Scotland and absent from the far north. With two or three broods per year, depending on altitude, the adults can be seen on the wing during warm weather anytime between May and October.

Widespread throughout Europe except northern Scandinavia, and extending deep into northern Africa, the Wall Brown's range stretches eastwards across Asia. Although colonies are mainly concentrated in lowland valleys, coastal cliffs and woodland edges, these butterflies use a very wide range of habitats and are sometimes seen at altitudes up to 3000m (10,000ft).

A male is shown in the upper picture and a female in the lower one. The wingspan range is 4.3 to 5.3cm.

Wall Brown resting on a coastal footpath
Underwing of a female Wall Brown

Numbers of Wall Browns in Britain have declined markedly since the 1990s, and habitat loss is probably the main factor in this decline, which is most noticeable in inland locations. A warming climate in Britain (and elsewhere in northern Europe) appears to be extending the northern limit of the range of this butterfly.

Lifecycle

The larval foodplants of this species are certain grasses (family Poaceae), including various bents (Agrostis spp.), meadow grasses (Poa spp.), Yorkshire Fog (Holcus lanatus), Tor-grass (Brachypodium pinnatum) and Cock's-foot (Dactylis glomerata).

THe pale green eggs are more or less spherical, and they become increasingly transparent as the larva develops, until it eats its way through the shell and begins feeding. The caterpillars are green and covered in short hairs. It is in its larval state - from the second brood - that this insect overwinters in Britain and Ireland.

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