Brown Argus - or is it?

[millerd]

I have been up in Yorkshire all week visiting relatives. One of the family excursions took us out to the Wolds Way Lavender Farm not all that far from Scarborough (SE872743 is a rough grid ref.).

One of the attractions on offer was a half-mile "nature walk" around the perimeter - this was blessed with informative boards at regular intervals describing likely sightings, including those of various butterflies. Despite overcast conditions, I quickly clocked up Meadow Browns, Small Coppers, Large Whites, a Red Admiral and a Small Skipper. One area had been sown with colourful wild flowers, and here I found what appeared to be a reasonably new female Brown Argus.

It was only afterwards I asked myself the question: How far north does the Brown Argus actually go? Beyond what point is it likely to be a Northern Brown Argus that you see, rather than the soft southern sort?

Here is the individual, from both above and underneath. My feeling is that the timing matches that of a second brood Brown Argus (though I think I've read that in the north they have just the one brood to confuse things).

Any answers/thoughts/musings welcome!

Dave

[David M]

Interesting questions posed.

I'm sure it's an Argus, but whether it's Northern Brown or just plain Brown is something the experts on here will have to tell you. There must be somewhere in the UK where these two species are in close proximity to one another if not overlapping.

Which side of the Maginot line are you on?

[Reverdin]

According to Butterflies of Yorkshire, H. Frost et al 2005...

There are 3 groups of argus in Yorkshire..
a) resident agestis
b) colonizing agestis, and..
c) resident artaxerxes

Resident agestis are small Wolds based colonies and usually single brooded, on Rockrose foodplant.
Colonizers are expanding through the region since c1997, geranium foodplant.

Yours could be either of the above, but perhaps more likely the colonizers,

artaxerxes are limestone grassland dwellers, utilizing Rockrose, some on the NYMoors but the majority in the Dales and Pennines where I live.

I have seen colonizer agestis 100 yards from where I live, but only once, this being less than 5 miles from the nearest artaxerxes colony nearby..
I hope this goes towards answering your enquiry.. the book is well worth a read if you can access it!

[millerd]

Fascinating stuff. This particular spot was very sandy soil, so given that, the timing and the freshness of the butterfly I think your conclusion about this one being a southern coloniser sounds spot on. It looks as if these infiltrators will very soon overlap with the Northern Brown Argus - Yorkshire will become a very complicated area for these two species.

Thanks,

Dave

[Piers]

To confuse matters there is a significant area of artaxerxes/salmacis hybrid.

Piers.

[millerd]

Given their close resemblance anyway, how on earth does anyone know this? I suppose the geneticists can tell, but for the rest of us precise identification in this part of the world is going to be at least partly guesswork!

Dave