Wall

Wall Lasiommata megera (Linnaeus 1767 )

Family: Nymphalidae, subgroup Satyrinae (The Browns)

Description

Photo above left by Chris Weston

Photo above middle by N Stables (same as header photo)

Photo above right by Phil Morgan

The Wall is an orange/brown butterfly with blackish/brown markings and white-pupilled eye-spots. Males have a dark brown band of scent scales on their upper forewings. Females are slightly larger with more rounded wings.

It is a very active species in sunshine and from a distance can look like a Dark Green Fritillary or a Comma though it has a quicker more zig-zagging flight pattern than either. They are restless butterflies which do not sit for long, but males usually remain within territories and guard them. In contrast to their fast movements when flying they spend some time basking in any sunshine on stone walls and bare paths, and are well camouflaged when still. By learning the type of places they like in any given area you can predict where they are likely to be basking and look ahead on paths and walls for them. The Wall particularly likes coastal paths.

They are around for 12 hours or more in the day when conditions are favourable, having been seen on the wing in Yorkshire from as early as 8am, until well into the evening, when they can be seen with outspread wings on west-facing walls, absorbing the last rays of warmth.

Habitat

The butterfly shows a distinct preference for open, unimproved grassland, hedge banks and lanes. It favours bare ground with rabbit holes and stones, but can also be seen in gardens, fields, woodland clearings, moorland, roadside verges, wasteland and the sides of ponds and rivers. lt is one of the few butterflies which may also be found in small to medium numbers in prairie landscapes, e.g. in Holderness, whilst roadside verges and the growing number of conservation headlands provide potential egg-laying habitat.

Regarding necessary larval foodplants it is thought that larvae need an essential mix of fine grasses in early life and coarse grasses later. Grass species used are Tor-grass (Brachypodium pinnatwn), False Brome (B. sy/vaticum), Sheep's Fescue (Festuca ovina), Yorkshire Fog (Holcus lanatus), Wavy Hair Grass (Deschampsia jlexuosa), Cocksfoot (Dactylis glomerata), Annual Meadow Grass (Poa annua), Common Bent (Agrostis capillaris), and Black Bent (A. gigantea).

Walls need warm, dry, habitats to help maintain a 25° to 30°C body temperature, and are extremely vulnerable to weather.

Distribution

The Wall is widespread throughout England and Wales, but absent or scarce in the higher regions of Wales and the Lake District. The species becomes more coastal north of Yorkshire, with its northern limit fluctuating considerably from year to year and in Ireland it tends to only be around the coast. In recent decades it has declined in southern and central England.

However there has been a slight increase in Yorkshire over recent decades with a widespread but fairly localised distribution through much of the county. It is more common in the southern half of Yorkshire, and towards coastal areas, but also in the Vale of York, extending northwards well north of York and eastward into the Hambleton and Howardian Hills.

In the past it wasn’t found in very high ground such as the higher areas of the Dales and North Yorks Moors but numbers have fluctuated a lot in recent years and the Wall’s range has extended into new areas of the Pennines VCs 63 and 64. Although it has a definite preference for warm, dry habitats, it is increasingly being recorded from exposed sites at high altitudes in the west and north of the county, e.g. near Holme (c300m VC63/SE10), Greenhow (c400m VC64/SE I6) and Whitcliffe Scar, west of Richmond (290m VC65/NZ1O).

It has successfully adapted to urban environments and can also be found along the field margins in areas of lowland arable agriculture. A proportion of Walls seem to be wanderers, giving them the ability to colonise new areas some distance from their areas of origin.

Life Cycle

Light green eggs are attached, usually singly, to the leaf tips, stems and exposed roots of a variety of grass species. Second brood females often lay on roots protruding through bank overhangs or rabbit holes.

The eggs become translucent after two to three days and hatch in about ten days. On emergence, the hairy, yellow-brown larvae eat their eggshells then feed mainly at night. They turn green at the second instar and bluish-green with pale stripes at the fourth (and final) instar, when they also feed by day and may wander between plants. First brood larvae take about a month to develop whilst most of the second brood hibernate over the winter and commence feeding again in spring.

Pupae vary from pale green to almost black and hang on, or nearby, typical foodplants. The pupal stage normally lasts two to three weeks, but it is thought that some second brood larvae pupate before winter and remain in this stage for seven months. In mild winters some larvae may continue feeding during the winter, and pupate in March to produce the occasional early butterflies observed in April.

First generation butterflies more usually appear in May or June, with the second generation in August or September. In good years the second generation may begin in July and when this happens, it is more likely that, given suitable autumn weather, there will be a partial third generation in late September or October. The trend in the last sightings dates suggest a regular trend towards a third generation. Earlier than usual first brood sightings have also been noted but in a poor spring the Wall may not appear until June.

Status

Section 41 species of principal importance under the NERC Act in England

Aberrations

There are over 40 variations described, affecting ground colour (golden brown to pale straw, white or even transparent), patterning, and eye-spots, which may be absent, altered in shape or multiplied. The reasons why it is so variable are not clear.

With thanks to The Butterflies of Yorkshire edited by Howard M Frost

Catherine Jones 18/11/20