UK Butterflies
Building a Community of Responsible Butterfly Enthusiasts in Britain & Ireland
Building a Community of Responsible Butterfly Enthusiasts in Britain & Ireland
Wingspan
♂ 44 - 48 mm, ♀ 46 - 52 mm
Checklist Number
59.008
Despite its name, the Scotch Argus is not only found in Scotland; it is also found at two sites in the north of England. A freshly-emerged Scotch Argus is a sight to behold, the dark brown velvety uppersides making the butterfly appear almost jet black from a distance. The butterfly is unmistakable when seen basking with its wings open, when orange bands containing distinctive spots are revealed. This butterfly lives in well-defined colonies that are often very large.
Like the Mountain Ringlet, the ability of this butterfly to survive cool temperatures means that it was probably one of the first species to recolonise the British Isles after the last ice age, over 10,000 years ago. The English colonies, Arnside Knott and Smardale Gill, are both found in Westmorland. Colonies are much more numerous in Scotland, where this butterfly can be found in most of northern, western and south-west Scotland. This butterfly is absent from the lowlands of central Scotland, many of the western isles (including the Outer Hebrides), Orkney and Shetland.
A colony at Grassington in Mid-west Yorkshire, famous for a particular race that had reduced orange markings, became extinct in 1923. According to Dennis (1977) "This colony which used to occupy parts of Grass Wood was last observed by Clutten in 1923. The orange markings on the upperside of the males were nearly obsolete; and this feature in the females was scarcely better developed than in ordinary males".
This species was first defined in Esper (1777) as shown here and as shown in this plate (type locality: Southern Germany).
The nominate subspecies is found in England and the north-east of Scotland.
This subspecies was first defined in Verity (1911a) as shown here and as shown in this plate (type locality: Galashiels, Scotland).
This subspecies is found in western and south-west Scotland although its distribution with regard to the nominate subspecies is by no means clear cut. The distribution shown here is taken from Thomson (1980). This subspecies differs from the subspecies aethiops as follows:
| Family: | Nymphalidae | Rafinesque, 1815 |
| Subfamily: | Satyrinae | Boisduval, 1833 |
| Tribe: | Erebiini | Tutt, 1896 |
| Genus: | Erebia | Dalman, 1816 |
| Subgenus: | ||
| Species: | aethiops | (Esper, 1777) |
| Subspecies: | aethiops | (Esper, 1777) |
| caledonia | Verity, 1911 |
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.
Despite experiencing a long-term decline in its distribution, this butterfly has increased at monitored sites and is not, therefore, currently a priority species 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).
1976-2014 (%) | 1976-2014 (%) | 2005-2014 (%) | 2005-2014 (%) |  -17 |  +170 | -18 |  +24 |
|---|
The flight period is fairly short for a butterfly that can appear in significant numbers. Butterflies emerge at the end of July, peaking in early August, with a few individuals surviving into September. There is one generation each year.
The adults are often the first butterflies of the day to be seen at suitable sites, their dark brown wings presumably allowing them to warm up more quickly than other species. They fly only when the sun is shining, and tend to retreat among grasses as soon as clouds appear, their undersides closely resembling a dead leaf. They reappear as rapidly when the sun comes out again and it is fascinating to watch an apparently-barren grassland come to life with butterflies as the clouds move away. Both sexes feed from a variety of nectar sources.
Males adopt both perching and patrolling strategies when in search of a mate. Males will fly for long periods when patrolling, searching out any dark brown object that is a potential mate. Females are mated shortly after they emerge with no discernable courtship involved, and the pair remain coupled for a few hours.
When egg-laying, the female selects sites that are in full sunshine and that are sheltered. She will bask for a while before crawling down into the grass and laying a single egg either on the grass or on nearby vegetation or debris. Eggs tend to be laid on Purple Moor-grass in Scotland and Blue Moor-grass in the Lake District.
Adults feed primarily on brambles (Rubus spp.), Devil's-bit Scabious (Succisa pratensis), Field Scabious (Knautia arvensis), hawkweeds (Hieracium spp.), Heather (Calluna vulgaris), knapweeds (Centaurea spp.), ragworts (Jacobaea spp.), thistles (Carduus spp. and Cirsium spp.) and Wild Marjoram (Origanum vulgare).
The spherical eggs are yellow when first laid, but turn light brown after a few days. This stage lasts between 2 and 3 weeks.
"Eggs laid August 10th, 1890, hatched on August 28th, remaining in the egg state eighteen days. Eggs laid August 11th, 1895, hatched on August 25th, being fourteen days in the egg state. The egg is large in proportion to the butterfly, being 1.3 mm. high, of an ovate globular form, but largest just below the middle, making the apical half slightly smaller than the basal half; the base is rounded; there are about twenty-five longitudinal triangular keels, which are finely ribbed transversely. Directly the egg is laid it is a pale primrose-yellow, which gradually deepens to ochreous or straw-yellow when two days old, with the crown slightly darker and spots just appearing over the surface. When five days old the spots are clearly defined. On the seventh day the ground colour is ochreous with a slight greenish tinge, and the spots dark purple. The extent and depth of the markings vary a good deal. They are in the form of blotches, distributed fairly evenly over the egg. Each blotch is composed of a number of minute speckles and streaks of purple-red, others deeper purple; some have the blotches more suffused, giving the egg a purplish appearance, and some specimens have the blotches a deep leaden-purplish. When ten days old the blotches become fainter, and the ground colour assumes a lilac-grey hue, finally the blotches gradually disappear and the markings of the larva become visible through the shell; these gradually increase in depth, and on about the twelfth day the larva is most clearly seen coiled up within, always in the same attitude, with its head fitting the crown of the egg and body obliquely coiled round, exposing its dorsal surface to view. it hatches on about the sixteenth day, according to temperature. The larva makes its exit by eating all round the crown (or nearly so), rather low down; it then pushes up the lid and crawls out; sometimes it eats a large portion of the empty shell." - Frohawk (1924)
When emerging from the egg, the larva nibbles around the top of the egg, but leaves a hinge, essentially creating a lid that it then opens. The eggshell is then partly eaten. Larvae feed during both day and night, but development is slow. Larvae hibernate while in the 1st or 2nd instar in leaf litter at the base of the foodplant. They emerge in the spring and mature larvae feed only at night, resting in ground debris during the day. There are 4 instars in total.
The primary larval foodplants are Blue Moor-grass (Sesleria caerulea), Purple Moor-grass (Molinia caerulea) and Sheep's-fescue (Festuca ovina). Cock's-foot (Dactylis glomerata), Common Bent (Agrostis capillaris), Common Couch (Elytrigia repens), Glaucous Sedge (Carex flacca), Sweet Vernal-grass (Anthoxanthum odoratum), Tufted Hair-grass (Deschampsia cespitosa) and Wavy Hair-grass (Deschampsia flexuosa) are also used.
"Directly after emergence the larva measures 2.5 mm. long. The head is large and globular, the surface granulated, of a pale ochreous colour, sparsely sprinkled with about sixteen short ochreous hairs or bristles, eye spots black and mouth parts brown; the body gradually tapers to the anal segment, which terminates in a square anal flap with six spines projecting from the sides and end, and two on the dorsal surface. The bases of the longest spines are rather swollen and form modified points, represented in other Satyridae larva. The segments are strongly wrinkled transversely on the dorsal surface; there are two longitudinal rows of small black warts, each emitting a short, slightly curved spine, one sub-dorsal and one super-spiracular, placed in pairs on each segment, and two others below each spiracle on the lateral ridge, which are again duplicated on the claspers. The ground colour is a very pale pearly-ochreous, striped longitudinally with rust colour; the most distinct stripe is medio-dorsal. The sub-dorsal stripe is much narrower. Then follows a broad super-spiracular band, on which are situated the warts, followed by a fainter spiracular line, enclosing the black spiracles; all these run the entire length, excepting the anal segment, which is uniformly whitish; the whole of the ventral surface, including the legs and claspers, is pearly-whitish; the entire surface is granular. The larva which hatched September 3rd, 1902, moulted first time September 21st, being eighteen days in the first stage. Others that hatched August 22nd, 1895, moulted first time September 14th, remaining twenty-three days in the first stage. Before first moult it measures 5 mm. long, and retains the light ochreous colouring as when first emerged, only showing more or less a very slight green tinge on the anterior dorsal surface. Late September-hatched larva fed and grew slowly, many being only in their first stage at the beginning of December, 1910, while others were in the second stage." - Frohawk (1924)
"After the first moult the head and body are densely clothed with short claw-like spines, each mounted on a conical base. The ground colour is a pale creamy-ochreous, striped longitudinally with light chocolate-brown, each line and stripe running the entire length; the sub-dorsal line is very fine, the super-spiracular line broad; between these two the ground colour is very pale, producing a whitish side stripe; a rather yellow lateral stripe bordered below by a brown band; the spiracles are black on a finer stripe. They are very sluggish in movement and rest during the day on the base of the grass stems. In October the larvae enter into hibernation, mostly in the second stage, but some in the first. They rest low down on the pale ochreous grass stems and withered blades of the same colour, which very closely resemble the larva, rendering them very inconspicuous. They remain motionless throughout the winter months, not feeding at all, as many of the Satyridae do, therefore they undergo complete hibernation. On March 22nd, 1911, a few became slightly active, and ninety-four had survived the winter; these were on the plants that had only occasionally received water by pouring it into the saucers in which the pots stood, and not by watering either plants or earth from the top; in this way the plants obtained just enough moisture by drawing up the water by the roots; by this means the grass itself kept dry, which appears necessary for the larva, as confined damp appears fatal to them in captivity when kept under any covering. During the last week of March many started feeding on different kinds of grasses. They feed during day, especially in the early morning. Several moulted the first time as late as the first half of April, while others that hibernated in the second stage moulted the second time during the latter half of that month. They gradually feed less by day, so that by the end of April they are nocturnal in their movements, and rest by day low down in the grass, and many assume a greenish tinge, making them less conspicuous. Before second moult it measures 8.5 mm. in length, the ground colour varies from pale creamy-ochreous to pale ochreous-greenish." - Frohawk (1924)
"After the second moult (a week after) it measures 12.7 mm. long while resting. The ground colour is pale grey-green, inclining to ochreous, the segmental divisions and lateral stripe pale ochreous; the medio-dorsal, sub-dorsal and super-spiracular stripes are purplish-drab, excepting the space between the two latter the surface is checkered with pale rust-brown; the body is densely sprinkled with ochreous club-shaped hairs, very minute, giving the larva a rough appearance, each with a whitish raised base. The head is roughly granular, of a pale ochreous-buff covered with similar hairs. In other respects it resembles the previous stage. They feed only at night, resting low down among the grass stems by day, and are very sluggish in movement." - Frohawk (1924)
"The third moult occurred on May 15th, 1911. After the third and last moult, fully grown, about 290 days old, it measures 22.2 mm. in length. It is rather stout in proportion, being thickest at the fifth and sixth segments and tapering at each end; the anal segment terminates in a pair of points; the ventral surface is flattened, with a rather dilated lateral ridge; the segments have five sub-divisions, each encircled with white warts, bearing serrated, slightly curved spines, which are whitish over the basal half and the apical half brown and with cleft tips. The head is pale ochreous-buff, granular and studded with similar but smaller bristles; the eye spots and mouth parts blackish. The normal ground colour is a very pale ochreous-yellow; the medio-dorsal stripe is dark olive-brown, broadest and darkest as it approaches the anal segment, bordered on each side by a stripe of the pale ground colour; the sub-dorsal surface is checkered with lilac-brown, then follows a sub-dorsal interrupted checkered line of the same colour and a broad pale band; a super-spiracular pale greenish-olive band, mottled and scrolled with olive-brown, bordered below by a pale line, and a spiracular band with fainter mottlings, and this again bordered by a lateral stripe, which is usually slightly more yellow than the rest of the ground colour; the ventral surface is similar to the dorsal, being checkered with lilac-brown; the legs and claspers are also ochreous-olive and studded with warts and hairs like the body; the spiracles are black. During their last stage the larva shun daylight by hiding at the base of the grass stems as low down as possible, where they rest all day and at sunset they commence to crawl up the stems to feed during the night. The resemblance between the larva of Epinephele tithonus and E. blandina in their last stage is remarkable, and they might readily be mistaken one for the other. The chief difference is, the hairs of tithonus are wholly whitish, with diverging cleft tips; the general ground colour is sometimes more tinged with diverging cleft tips; the general ground colour is sometimes more tinged with greenish-yellow; the lateral stripe is whiter and more sharply defined and bordered above by a deep claret-brown line. When ready for pupation the larva forms a slight hollow on the surface of the ground at the base of the grass, and spins a loose open network cocoon over itself and settles in a more or less upright position, head uppermost, and finally pupates. The first one pupated June 23rd, 1911." - Frohawk (1924)
The pupa is formed in a loose cocoon, typically in mosses or some other soft material. This stage lasts between 2 and 3 weeks.
"The pupa measures 12.7 mm. long, the general shape is rounded and rather stout in proportion. Dorsal view: Head bluntly formed, slightly concave behind eyes, giving a slight angle at the base of the wings; very little sunken across the middle, swelling at the third and fourth abdominal segments, then tapering abruptly to the anal segment, which terminates in a broad, truncated cremaster. Lateral view: Head and thorax rounded; the meta-thorax is on a plane with abdomen, which has a slight depression between third and fourth segments; remaining segments abruptly tapering; cremaster decurved; wings ample, reaching to fifth segment, and swollen at the middle. The whole surface is finely granulated and, excepting the wings, is sparsely sprinkled with minute stumpy bristles. At first the colour is a very pale fleshy-ochreous and semi-transparent, the abdomen rather deeper ochreous than the wings and thorax; as it matures the colouring deepens and becomes more opaque, with a greyish hue over the median wing area and a few dark leaden underlying specks; margin of wing yellow-ochreous; abdomen amber-ochreous. A medio-dorsal and a pair of finer sub-dorsal stripes of darker amber-brown, also a faint sub-spiracular stripe of same colour; spiracles brown. of same colour; spiracles brown. Before emergence the eyes darken and the wings turn an opaque cream colour; then the sub-marginal wing spots appear and the whole pupa gradually darkens until it finally assumes a deep bluish-black; the sub-marginal wing spots then show indistinctly dull reddish. The first, which pupated June 23rd, emerged July 9th, 1911, remaining sixteen days in the pupal state, followed by others daily for the following five days, their emergence being hurried by the continuance of exceptionally warm weather: over 80 degrees Fahr. shade temperature daily, on the 12th reaching 84 degrees Fahr. at 8 p.m." - Frohawk (1924)
The following links provide additional information on this butterfly.
