Scotch Argus

Erebia aethiops (e-ruh-BEE-uh EE-thee-ops)

Scotch-Argus- 5D32869 Arnside Aug 2012
Photo © IainLeach
 

Wingspan
Male: 44 - 48mm
Female: 46 - 52mm

Checklist Number
59.008

Family:NymphalidaeRafinesque, 1815
Subfamily:SatyrinaeBoisduval, 1833
Tribe:ErebiiniTutt, 1896
Genus:ErebiaDalman, 1816
Subgenus:  
Species:aethiops(Esper, 1777)
Subspecies:aethiops (Esper, 1777)
 caledonia Verity, 1911

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Introduction

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".

Erebia aethiops ssp. aethiopsHistoric Specimens

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.

Scotch-Argus- 5D35205 Arnside Aug 2012

Male
Photo © IainLeach

Scotch-Argus-Arneside Knott 30 July 2011 03C4023

Male Underside
Photo © IainLeach

Scotch Argus - female - Arnside Knott - 28-Jul-14

Female
Photo © Pete Eeles

Scotch-Argus- 5D33883 Arnside Aug 2012

Female Underside
Photo © IainLeach

Photo Album ...


Erebia aethiops ssp. caledonia

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:

  • 1. Invariably smaller size.
  • 2. Forewings narrower and more elongated, with sharper angles and a straighter wing edge.
  • 3. The reddish yellow band is narrower and never contains more than three small eye spots.
  • 4. The bands on the underside of the hindwings are frequently indistinct.
Scotch Argus - male - Glen Kinglas - 17-Aug-15-4

Male
Photo © Pete Eeles

Scotch Argus - male - Glasdrum Wood - 17-Aug-15-17

Male Underside
Photo © Pete Eeles

Scotch Argus - female - Glasdrum Wood - 17-Aug-15

Female
Photo © Pete Eeles

Scotch Argus - Isle of Mull 30-July-2013

Female Underside
Photo © Jack Harrison

Photo Album ...


History

The table below shows a chronology of vernacular names attributed to this species. Any qualification of the name (e.g. male, female) is shown in brackets after the name.

YearNameReference
1807Scotch ArgusDonovan (1807)
1832Scotch RingletRennie (1832)
1871Northern BrownNewman (1871)

Conservation Status

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.

UK BAP StatusOccurrence Change
1976-2014 (%)
Abundance Change
1976-2014 (%)
Occurrence Change
2005-2014 (%)
Abundance Change
2005-2014 (%)
Not Listed
Decrease-17
Large Increase+170
Decrease-18
Increase+24

The table above 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).

Habitat

Most colonies are found in sheltered and damp areas. Bogs, woodland edges and riverbanks where the foodplant grows are typical habitats. The English colonies are situated in a different type of habitat, where sites are limestone grassland sheltered by adjoining woodland.

Distribution

 

Click here to see the distribution of this species or here to see the distribution of this species together with specific site information overlaid.

Life Cycle

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.

Erebia aethiops ssp. aethiops

Erebia aethiops ssp. caledonia

The chart(s) above have been correlated with the phenology plot below, taken from the UK Butterfly Monitoring Scheme. The blue line gives average counts over the full data set from 1976 to date, and the red line gives the average for the last year.

Imago

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 Devil's-bit Scabious (Succisa pratensis), Field Scabious (Knautia arvensis), Heather (Calluna vulgaris / Erica spp.), Knapweeds (Centaurea spp.), Marjoram (Origanum vulgare), Ragwort (Senecio jacobaea) and Thistles (Cirsium spp. and Carduus spp.).

Erebia aethiops ssp. aethiopsHistoric Specimens

Scotch Argus - male - Arnside Knott - 28-Jul-14-16

Photo © Pete Eeles
28-Jul-2014

Scotch Argus - imago - Arnside Knott - 12-Jul-05

Photo © Pete Eeles
13-Jul-2005

Scotch Argus female - Arnside Knott 01.08.2017

Photo © Neil Freeman
01-Aug-2017

Scotch-Argus- 5D35205 Arnside Aug 2012

Photo © IainLeach

Scotch Argus - male - Arnside Knott - 28-Jul-14-12

Photo © Pete Eeles
28-Jul-2014

Scotch-Argus-Arneside Knott 30 July 2011 03C4072

Photo © IainLeach

Scotch Argus - male - Arnside Knott - 28-Jul-14-11

Photo © Pete Eeles
28-Jul-2014

Scotch Argus - female - Arnside Knott - 28-Jul-14-2

Photo © Pete Eeles
28-Jul-2014

Scotch Argus pair in cop. - Arnside Knott 5.08.2013

Photo © Neil Freeman
05-Aug-2013

Scotch-Argus-Arneside Knott 30 July 2011 03C3912

Photo © IainLeach

Scotch Argus - Mating Pair - Arnside Knott, Cumbria - 27th July 2012

Photo © Graham Beckwith

Scotch-Argus- 5D35729 Arnside Aug 2012

Photo © IainLeach

Scotch Argus - male - Arnside Knott - 28-Jul-14

Photo © Pete Eeles
28-Jul-2014

Arneside Knott   25.07.11

Photo © Tony Moore
26-Jul-2011

Scotch-Argus-Arneside Knott 30 July 2011 03C4657

Photo © IainLeach

Scotch Argus - male - Arnside Knott - 28-Jul-14-13

Photo © Pete Eeles
28-Jul-2014

Scotch Argus Male - Arnside Knott, Cumbria 28-July-10

Photo © Vince Massimo
28-Jul-2010

Scotch Argus - imago - Arnside Knott - 22-Jul-05 [Alan Thornbury]

Photo © Alan Thornbury

Scotch-Argus-Arneside Knott 30 July 2011 03C7238

Photo © IainLeach

Scotch Argus - Arnside Knott, Cumbria 29-July-10

Photo © Vince Massimo
29-Jul-2010

Photo Album (46 photos) ...


Erebia aethiops ssp. caledonia

Scotch Argus - female - Glen Kinglas - 17-Aug-15-8

Photo © Pete Eeles
17-Aug-2015

Scotch Argus - female - Glasdrum Wood - 17-Aug-15

Photo © Pete Eeles
17-Aug-2015

Scotch Argus - Isle of Mull 4-Aug-2013 (3)

Photo © Jack Harrison

Scotch Argus - male - Glasdrum Wood - 17-Aug-15

Photo © Pete Eeles
17-Aug-2015

Scotch Argus - male - Glasdrum Wood - 17-Aug-15-13

Photo © Pete Eeles
17-Aug-2015

Scotch Argus - male - Glasdrum Wood - 17-Aug-15-11

Photo © Pete Eeles
17-Aug-2015

Scotch Argus - female - Glasdrum Wood - 17-Aug-15-3

Photo © Pete Eeles
17-Aug-2015

Scotch Argus - Isle of Mull 4-Aug-2013 (2)

Photo © Jack Harrison

Scotch Argus - female - Glasdrum Wood - 17-Aug-15-4

Photo © Pete Eeles
17-Aug-2015

Scotch Argus - male - Glasdrum Wood - 17-Aug-15-12

Photo © Pete Eeles
17-Aug-2015

Scotch Argus - Isle of Mull 30-July-2013

Photo © Jack Harrison

Scotch Argus - male - Glasdrum Wood - 17-Aug-15-16

Photo © Pete Eeles
17-Aug-2015

Scotch Argus - male - Glen Kinglas - 17-Aug-15

Photo © Pete Eeles
17-Aug-2015

Scotch Argus ssp. caledonia - male - Glasdrum Wood, Scotland - 17-Jul-14

Photo © Pete Eeles
17-Jul-2014

Scotch Argus - imago - Ardnamurchan - Unknown date [Adrian Riley]

Photo © Adrian Riley

Scotch Argus - male - Glasdrum Wood - 17-Aug-15-17

Photo © Pete Eeles
17-Aug-2015

Scotch Argus - female - Glen Kinglas - 17-Aug-15-7

Photo © Pete Eeles
17-Aug-2015

Scotch Argus - Isle of Mull 30-July-2013 (2)

Photo © Jack Harrison

Scotch Argus - Isle of Mull 4-Aug-2013

Photo © Jack Harrison

Scotch Argus - female - Glen Kinglas - 17-Aug-15-6

Photo © Pete Eeles
17-Aug-2015

Photo Album (24 photos) ...


Ovum

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)

Scotch Argus - ovum - Unknown location - Unknown date (2) [REARED] [Reg Fry]

Photo © Reg Fry

Scotch Argus - ovum - Unknown location - Unknown date [REARED] [Reg Fry]

Photo © Reg Fry

Scotch Argus - ovum - Vaud, Switzerland - 31-Jul-06 [Guy Padfield]

Photo © Guy Padfield

Scotch Argus - ovum - Arnside Knott - 05-Aug-14

Photo © Pete Eeles
05-Aug-2014

Scotch Argus - ovum - Arnside Knott - 29-Jul-14

Photo © Pete Eeles
29-Jul-2014

Scotch Argus - ovum - Arnside Knott - 30-Jul-14-3

Photo © Pete Eeles
30-Jul-2014

Scotch Argus - ovum - Arnside Knott - 30-Jul-14-4

Photo © Pete Eeles
30-Jul-2014

Scotch Argus - ovum - Arnside Knott - 30-Jul-14

Photo © Pete Eeles
30-Jul-2014

Photo Album (8 photos) ...


Larva

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) and Purple Moor-grass (Molinia caerulea).

Scotch Argus - larva - Thatcham - 01-May-05 [REARED]

Photo © Pete Eeles
03-May-2005

Scotch Argus - larva - Thatcham - 16-May-05 (2) [REARED]

Photo © Pete Eeles
17-May-2005

Scotch Argus - larva - Thatcham - 16-May-05 [REARED]

Photo © Pete Eeles
17-May-2005

Scotch Argus - larva - Unknown location - Unknown date [REARED] [Reg Fry]

Photo © Reg Fry

Scotch Argus - larva - Thatcham - 23-Apr-14 [REARED]

Photo © Pete Eeles
23-Apr-2014

Photo Album (5 photos) ...


1st Instar

"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)

Scotch Argus - larva - Unknown location - Unknown date (4) [REARED] [Reg Fry]

Photo © Reg Fry

Scotch Argus - larva (1st instar) - Thatcham - 10-Aug-14 [REARED]

Photo © Pete Eeles
10-Aug-2014

Photo Album (2 photos) ...


2nd Instar

"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." - Frohawk (1924)

3rd Instar

"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)

4th Instar

"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)

Scotch Argus - larva - Glen Kinglas - 11-Jun-15

Photo © Pete Eeles
11-Jun-2015

Photo Album (1 photos) ...


Pupa

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)

Scotch Argus - pupa - Thatcham - 13-Aug-12 (1) [REARED]

Photo © Pete Eeles

Photo Album (1 photos) ...


Aberrations

Description to be completed.

Click here to see the aberration descriptions and images for this species.

Similar Species

Mountain Ringlet

Description to be completed.

Videos


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References

The species description provided here references the following publications:

ReferenceDetails
Boisduval (1833) Boisduval, J.A. (1833) Icones historiques des Lépidoptères d'Europe nouveaux.
Dalman (1816) Dalman, J.W. (1816) Kongl. Svenska Vetenskaps akademiens Handlingar.
Dennis (1977) Dennis, R.L.H. (1977) The British Butterflies - Their Origin and Establishment.
Donovan (1807) Donovan, E. (1807) The Natural History of British Insects (Vol.12).
Esper (1777) Esper, E.J.C (1777) Die Schmetterlinge in Abbildungen nach der Natur mit Beschreibungen.
Frohawk (1924) Frohawk, F.W. (1924) The Natural History of British Butterflies.
Newman (1871) Newman, E. (1871) An Illustrated Natural History of British Butterflies.
Rafinesque (1815) Rafinesque, C.S. (1815) Analyse de la nature ou Tableau de l'univers et des corps organisés.
Rennie (1832) Rennie, J. (1832) A conspectus of the butterflies and moths found in Britain, with their English and systematic names, times of appearances, sizes, colours, their caterpillars, and various localities.
Thomson (1980) Thomson, G. (1980) The Butterflies of Scotland.
Tutt (1896b) Tutt, J.W. (1896) The Classification of British Butterflies. Entomologist's Record and Journal of Variation.
Verity (1911a) Verity, R. (1911) Races inédites de Satyridae européens [Lep. Rhopalocera]. Bulletin de la Société Entomologique de France.