www.ukbutterflies.co.uk

Hi, perhaps a forum member could teach me a little about the Northern Brown Argus

Firstly, what are the visible differences between the two British Brown Argus species?

Secondly, what is the butterfly's range here? This site appears to show it living no further south than Lancashire and Yorkshire, but the UKBAP and NBN database show it clearly recorded as far south as Derbyshire...

Here's an example I'd like identified, any help much appreciated ...hopefully with the info above though I'll be able to say myself which it is

Alexander

Hi
It looks like a common blue to me.
Stan.

It looks to me like ssp. salmacis of the northern brown argus. The pattern of spots on the underside hindwing mean it is either brown argus or northern brown argus (the two nearest the leading edge of the hindwing make a colon pattern, out of series with the other spots) and the wing shape suggests northern brown argus to me (brown argus is less pointy at the apex). However, I'd much rather see an upperside to be sure of this!! Brown argus has a more complete set of orange lunules on the forewing, though you need to take sex into account when judging this as males of both species are less complete than females.

Any upperside shots?

Guy

Aricia appear in three phases in UK. Agestis is the usual Brown Argus, which reaches it's northernmost extremity here in the North East. Then there is artaxerxes which extends from about here up to the far North. Overlapping both there is salmacis which is to an extent held to be a hybrid by some. Much genetic study has been done. The artaxerxes is more closely related to the continental allous than agestis, and there is little evidence of hybridization and salmacis seems to be closer to artaxerxes.
The delineation between all of these is not clear, and individual variations overlap making ID difficult. Derbyshire Peak District does have NBA colonies, and there are more on the West side of the country, further South than on the East side. White spot NBAs appear in Dumfries and Berwickshire Northwards, though partial white spots I have seen further south, eg. here in Swaledale. The degree of orange upperside spotting is the usual way of judging
I have seen agestis 100yds from my house, which is itself 3 miles from NBA colonies. Further mixing seems inevitable.

Finally, there is a great article in the Book "The Butterflies of Yorkshire" produced by BC Yorkshire.. I like the book a lot!!

agestis...




salmacis...




artaxerxes...




and allous...

Thanks Paul and Guy for the education, I'll know what to look for in the future.

I think this one is ssp salmacis then. I can see what you mean about the wing apex shape. The upperside orange lunules are bolder than Paul's example of salmacis but are equivalent to others photographed on the NBA (salmacis) species page.

It was photographed in the Peak District btw.

Alexander