UK Butterflies

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Wall

Lasiommata megera

LASS-ee-oh-may-tuh muh-JEE-ruh

Wingspan
45 - 53 mm

Checklist Number
59.002

Wall

Lasiommata megera

LASS-ee-oh-may-tuh muh-JEE-ruh

Wingspan
45 - 53 mm

Checklist Number
59.002


The Wall gets its name from the characteristic behaviour of resting with wings two-thirds open on any bare surface, including bare ground and, of course, walls! Many people will have come across this butterfly on footpaths, especially in coastal areas, where the butterfly flies up when disturbed, before setting again a few metres ahead.

The basking behaviour of this butterfly allows it to benefit from the full warmth of the sun whose rays shine directly on the butterfly, but also get reflected back onto the butterfly from whichever surface it is resting on. This habit allows the butterfly to raise its body temperature sufficiently high for it to fly. In particularly hot weather, however, such basking is avoided and the butterfly may even retreat to a suitably-shaded spot to avoid overheating.

This species was once found throughout England, Wales, Ireland and parts of Scotland. Today, however, is a very different picture, with this species suffering severe declines over the last several decades. It is now confined to primarily-coastal regions and has been lost from many sites in central, eastern and south-east England. In Scotland it is confined to coastal areas in the south-west of the country. It is also found on the Isle of Man and Channel Islands. This butterfly is found in relatively small colonies that are self-contained although some individuals will wander, allowing the species to quickly colonise suitable nearby sites.

This species was first defined in Linnaeus (1767) as shown here (type locality: Austria and Denmark).

Description to be completed.

The distribution data (2000-2009) has been made available through the generosity of Butterfly Conservation and any subspecies distribution is taken from Riley (2007). Click here to see the distribution of this species together with site information overlaid.

This species is now found primarily in coastal areas, especially unimproved grassland, wasteland, cliff edges and hedgerows.

There has been a severe and worrying decline of inland populations, with most remaining populations now being found in coastal areas. This species is therefore a priority for conservation efforts.

The table below shows the occurrence (distribution) and abundance (population) trends, using information from The State of the UK's Butterflies 2015 (Fox, 2015). Any UK BAP status is taken from the UK Biodiversity Action Plan (UK BAP) (2007 review).

UK BAP Status
Occurrence Change
1976-2014 (%)
Abundance Change
1976-2014 (%)
Occurrence Change
2005-2014 (%)
Abundance Change
2005-2014 (%)
Priority Species
Click here to access the Biodiversity Action Plan (BAP).
Large Decrease -77Large Decrease -87Decrease -36Decrease -25

The first generation of adults emerge in early May, peaking at the end of May and early June, or a little later in the north of England and Scotland. They give rise to a second brood that emerges at the end of July, or mid-August further north. There are 2 generations each year and, on occasion, a small 3rd generation may appear in October.

The male of this species is territorial and will inhabit a particular area, such as a path, hedgerow or roadside verge, waiting for a passing female. Males will typically perch in a favoured position but will, in sunny and warm conditions, adopt a strategy of patrolling in order to find a mate. All passing insects are investigated and rival males will fly high into the air before coming back to the ground a few seconds later.

The female is much more sedentary and the less-conspicuous of the two sexes. After a brief courtship a pair will mate before disappearing into surrounding vegetation. Both sexes are avid nectar feeders and will feed from any available flower.

Adults feed primarily on Common Fleabane (Pulicaria dysenterica), Daisy (Bellis perennis), hawkweeds (Hieracium spp.), knapweeds (Centaurea spp.), Ragged-Robin (Silene flos-cuculi), ragworts (Jacobaea spp.), thistles (Carduus spp. and Cirsium spp.), Water Mint (Mentha aquatica), Wild Marjoram (Origanum vulgare) and Yarrow (Achillea millefolium).

The spherical eggs are laid singly, or occasionally in twos and threes, in various positions, including the leaves of the foodplant, exposed roots and nearby vegetation. Eggs are pale green when first laid, becoming more translucent as the larva develops within. Sites for egg-laying are typically sheltered and warm compared to their surroundings, and include grass clumps, rabbit scrapes and hoof prints from cattle. This stage lasts around 10 days.

"Ova deposited June 2nd, 1890, hatched June 13th, being eleven days in the egg state. Ova deposited August 2nd, 1893, hatched August 11th, the egg state lasting only nine days, owing to the very warm summer. The eggs are laid singly on the blades of grasses. In captivity the females deposit freely on Poa annua. The egg is spheroidal in shape, 0.91 mm. in height; it is large in proportion to the butterfly. The surface is finely granulated with an irregular network pattern, which becomes more regular round the middle, where it runs into parallel longitudinal rows, giving it a slightly fluted appearance (over the central third) with transverse ribs; otherwise the surface appears quite smooth to the naked eye. When first laid the colour is a yellowish-green-white, and remains unchanged until shortly before hatching, when it becomes semi-opaque and encircled with dark grey and blackish streaks, produced by the long black hairs of the larva showing through the shell, and the crown is blotched with dark leaden-grey and ochreous." - Frohawk (1924)

After emerging, the young larva typically eats its eggshell before feeding on the leaves of the foodplant. Larvae become more mobile as they mature and will move from plant to plant as needed. Larvae typically feed at night, but occasionally feed during the day. This stage lasts around 4 weeks for those larvae that do not overwinter, and there are 3 moults in total.

The primary larval foodplants are bents (Agrostis spp.), Cock's-foot (Dactylis glomerata), False Brome (Brachypodium sylvaticum), Tor-grass (Brachypodium rupestre), Wavy Hair-grass (Deschampsia flexuosa) and Yorkshire-fog (Holcus lanatus).

1st Instar

"Directly after emergence the larva measures 2.5 mm. long; the body is gradually attenuated from the head. There are ten longitudinal rows of shining pale olive or ochreous-grey, short, blunt tubercles; those above the spiracles emit long, curved black hairs, and those below straight and shorter hairs; those forming the dorsal rows are very long and curve backwards, while those of the of series curve forwards; the sub-spiracular series is composed of a pair of tubercles on each segment, each bearing long, straight, whitish hairs diverging at their tips and approximated at the base; on the legs and claspers is a similar series, but each pair with the base united; the spiracles are very small and black. There are three longitudinal rust-coloured lines — two sub-dorsal and one spiracular. The ground colour is pale ochreous-yellow, becoming white below the spiracles and on the ventral surface. The body is slightly wrinkled transversely and granular. The head is large, pale ochreous with twelve black dots, and four others united forming a A in the centre; the black eye spots are placed on another dark patch; from the centre of each spot rises a rather long black hair with a whitish tip and a rather bulbous base, all curving forwards; the legs and claspers are the same colour as the ventral surface. The first meal consists of nearly all the egg-shell, which it consumes upon emerging and leaves only a saucer-like base; as soon as this meal is finished it quickly starts feeding on the grass blades upon which the eggs are laid. Before first moult it measures 6.3 mm. long; the body has now attained a cylindrical shape, being of uniform thickness throughout, and entirely of a pale delicate green, with darker green dorsal and sub-dorsal lines, also a whitish lateral stripe; the head is pale green with black spots; otherwise it is similar to the previous description. They feed chiefly at night and spend the day resting on the grass in a straight position." - Frohawk (1924)

2nd Instar

"First moult June 22nd, 1890, the first stage lasting nine days. After the first moult, twelve days old, it measures 8 mm. long; the ground colour is green, with a darker dorsal stripe, edged with a whitish line, and a clearly defined white lateral line; the spiracles are pale in colour; between the medio and sub-dorsal lines is a pale, indistinct, broken whitish line, which is also repeated between the sub-dorsal and lateral lines, the whole making a pattern of alternate dark and light stripes." - Frohawk (1924)

3rd Instar

"Second moult June 28th, the second stage lasting six days. After the second moult (five days after) it is 12.7 mm. in length; the colour is a clear light green, the medio-dorsal line is slightly darker than the ground and bordered with a fine pale line, a similar pale line down the side, and a whitish lateral line; these three lines are placed at equal distances and between each is a very indistinct wavy line. The head, legs and claspers are the same colour as the body. Both head and body are covered with very minute warts, each bearing a fine hair; the anal points are whitish. This species normally passes the winter as a larva when in the third stage, i.e., after the second moult; but only undergoes partial hibernation, as it feeds at times throughout the winter whenever the weather is mild enough." - Frohawk (1924)

4th Instar

"The third and last moult occurred on July 5th, the third stage lasting seven days. The larvae became fully grown on July 14th and pupated July 16th, the last stage lasting nine days. After the third moult, thirty-one days old, it measures 24 mm. in length. The ground colour of both head and body is a rich green with a slight bluish tinge, a darker green medio-dorsal stripe bordered with a very fine whitish line, and three indistinct pale lines at equal distances apart along the side; the central one is hardly discernible; on the lowest one are placed the pale orange spiracles, and below is a whitish lateral stripe bordered by fine dark lines; the head is a purer green than the body; the legs are greenish-white and semi-transparent, the claspers green, the anal points light green. Both head and body are beset with minute white warts, each emitting a fine hair, giving the entire surface a somewhat rough, downy appearance. The body tapers at each end, but mostly so posteriorly. When about to pupate it spins a small pad of silk on a stem of grass, and, attaching itself by the anal claspers, it hangs suspended in the form of a hook, with its anterior end curved upwards with the head reaching to between the eighth and ninth segments; in this attitude it remains for about forty hours and then pupates." - Frohawk (1924)


The green pupa is formed head down, attached by the cremaster to the foodplant or nearby vegetation and is extremely well camouflaged. This stage lasts around 2 weeks.

"The pupa averages 15.9 mm. long. It is well proportioned; the head is rather broad and angulated in front, the thorax much swollen and keeled dorsally, sunken at the waist; the dorsal outline of the abdomen forms a graceful curve and the ventral outline is nearly straight; the wings are swollen near the apex, projecting and angular at the base; along the dorsal surface are two series of white, stud-like tubercles, the second, third and fourth being considerably the largest and most prominent; the spiracles are whitish; the general structure is outlined with whitish, and a medio-dorsal abdominal stripe darker than the ground colour, also a similar sub-dorsal line and a paler lateral line. The surface of the pupa is sprinkled with creamy-white granulations, especially along the wing nervures. The dorsal creamy-white points are very conspicuous on the deep black pupa. The anal segment terminates in a long cremaster, amply furnished with hooks, by which the pupa is suspended to a pad of silk spun to a grass stem or some suitable object. The Wall The pupa varies extremely in colour, from grass-green to deep black. The normal colour is green of more or less purity. The grass-green form is palest and inclining to yellowish on the abdomen. After about ten days the colouring becomes more opaque, the wings especially so, and the sub-dorsal line disappears, and finally it darkens all over before emergence." - Frohawk (1924)