Northern Brown Argus

Northern Brown Argus Aricia artaxerxes (Denis & Schiffermüller 1775)

Family: Lycaenidae, (The Blues)


Photos by Martin Partridge

The Northern Brown Argus has a warm, deeper chocolate brown, ground colour to the upper wings than the Brown Argus, and the same striking white wing margins when fresh. The butterflies average wingspan is around 30mm. There may well be a visible discal spot on each forewing, sometimes just black and sometimes with a white circle around it. The orange crescents (“lunules”) on all four wings vary in number an intensity of colour. The females of the species with regards to identification, photographs are always very helpful, particularly underwing shots.

The best way to tell the Northern Brown Argus and female Common Blue apart is to look at the underwing. The Northern Brown Argus has two of its rear underwing dots in a figure of 8 or colon (:) arrangement. The Common blue has them in a continuous arc the two dots being in a line (. .) .There is also a dot missing on the forewing of the Brown Argus when compared to the Common Blue. (see photos)

Separating the Northern Brown Argus (A.artaxerxes) from the Brown Argus (A.agestis) is now almost impossible in our region unless you are in a geographic area which is known only to have Brown Argus or Northern Brown Argus populations. In areas where they now may overlap in VC65 and VC66 only genetic analysis is likely to be able to tell them apart.

In the past there were a number of accepted methods to distinguish the two, but these are all now considered unreliable. These include using differences in the upper wing discal spots. The Brown Argus A. agestis (with black spots), Northern Brown Argus A. artaxerxes (with white spots) and Northern Brown Argus subspecies A. salmacis (with black and white spots) which was in the past recognized as coming from the Castle Eden Dene area in VC66 and stretching over to southern Cumbria.

White scales, and even the all-white discal spot, can occasionally appear throughout the Northern Brown Argus range becoming more frequent as one heads north. Likewise, within the former A. salmacis range, a proportion of butterflies still show black discal spots. The number of white scales appearing in either group varies from a single scale to a white patch or even a complete ring of scales around the black discal spot. However, the range of variation means that individuals cannot be cited as having diagnostic features either in Yorkshire or elsewhere.

It is often noted that the Northern Brown Argus is single brooded (Univoltine) and the Brown Argus is double brooded (Bivoltine) but this is also not a reliable indicator.


Northern Brown Argus resident populations appear to be sedentary one-generation populations linked to common rock-rose on limestone grassland/limestone pavement habitats. The butterfly likes shelter and warmth and favours south-facing sites which contain hollows or areas with an amount of scrub.


Northern Brown Argus resident populations appear to be sedentary one-generation populations linked to common rock-rose on limestone grassland/limestone pavement habitats, and spread across a small number of 10km squares in the Yorkshire Dales in VC64 around Ingleton, Settle and North east from there, and VC65 around the Aysgarth & Richmond areas.

Life Cycle

The Northern Brown Argus populations on Common rock-rose can be single brooded (Univoltine) (May/Jun) but may produce a partial 2nd brood (Bivoltine) in good years (Aug/Sept).

The first sighting of the Northern Brown Argus in 2020 were made on 20/05 at Lea Green near Grassington in VC64. This is the earliest record for the UK ever recorded for the emergence of Northern Brown Argus.

The last sighting in 2020 was at Ballowfields Nature Reserve on the 09/09 in VC65, this is likely to be an a slightly unusual second brood, given the location being a known Northern Brown Argus site and the very early first brood observed in 2020.

The eggs are laid singly, on common rock-rose leaves, typically on the upper surfaces. The female in looking for places to egg lay is seen flying close to the ground seeking out suitable foodplants tasting them with her feet until she finds a suitable place when she lays a single egg on the upperside of a leaf.

Eggs appear as squat, whitish spheres, found from mid-June on low-lying sheltered situations in the south of the county, and from early July further north and higher up. Microscopic examination reveals that eggs have a very variable reticulated surface structure. Larvae hatch out after about two weeks, and crawl to the underside of the leaf, where they eat small areas, leaving the upper leaf surface intact. The affected surface of the leaf tends to turn yellow after a short time. Green woodlouse-shaped larvae are well-marked with green chevrons and black heads. Northern Brown Argus larva have a dark green dorsal line (down the middle of the back) but such lines vary significantly. The sub-spiracular line, (low down on both sides) varies from white, with purplish pink above and below the white, to white with virtually no colours on either side. In autumn, larvae of the third instar hibernate at the bottom of the foodplant or under a leaf and become active again in early spring probably in late February, early March.

A couple weeks after feeding the larva moults in to a fourth instar. The feeding habitats now change with the larva breaking through the upper surface of the leaf edge. After around a further 10 days the larva moults for the final time into a fifth instar. When fully grown by late May it prepares to pupate. Pupation takes place on or near the ground and ants may attend both larvae and pupae. We know little about the part played by ants in Yorkshire. Sam Ellis (1997) has observed Formica lemani attending larvae of Northern Brown Argus on a Durham site, but inferred this was probably a fairly rare occurrence. There is scope for further study here.


The Northern Brown Argus is listed as a priority species in the Biodiversity Action Plan for the Dales National Park, and efforts are being made to manage all suitable unoccupied habitat within 5km of known colonies.


UK BAP status: Priority species.

BC priorities: National: High. N of Eng: High.

Yorkshire: High.

European status: Not threatened.

Protected from sale in GB.

Resident, 0-2800m: usually 1 brood, but small partial 2nd appears possible in good years even in Scotland (mid-Jun/late Jul, Aug/Sep). Recorded in 30 European countries: declines reported in 8, and listed as an RDB species in 9. As a result of difficulties over status throughout its range, there are doubts about which part of the genus occurs in various localities, therefore, the range of the whole Argus/Aricia genus is summarised here: it includes the Canary Islands, the Atlas Mountains in N Africa (Morocco to Tunisia), Iran, the whole of Europe, and eastward through the northern half of Asia to Siberia and Amur. In Britain the Brown Argus is mainly found east of a line from the Severn to the Humber, with a scatter of mainly coastal colonies in the west as far north as N Wales. The Northern Brown Argus ranges from Lancashire, Cumbria and the northern Pennines in Yorkshire, into SW and E Scotland.


Only a dozen specific aberrations have been described for the Northern Brown Argus, mainly covering variations in amounts of white around the discal spot, (although some aberrations described for Brown Argus also apply). Occasionally all four upperwings carry a white discal spot (ab quadripuncta Tutt).

Martin Partridge 15/01/21