In search of the Durham brown argus

Today we were out in search of the Durham brown argus butterfly! We carry out yearly surveys on a stretch of the Durham coast, to check on populations of this butterfly and to outline any immediate work, and long term management that may be needed to help protect it.

The Durham brown argus (Aricia artaxerxes salmacis) is a nationally scarce species of butterfly. It is actually a sub-species of the Northern brown argus (Aricia artaxerxes) and is only found in northern England.

Areas of the Durham coast with south facing slopes where there is an abundance of the butterflies larval foodplant, Common rock-rose, offer a good chance to catch a glimpse of the butterfly.

The Durham brown argus has a single brood and adults emerge in early June, peaking at the end of June – so the window to see them is reasonably small. Also, although populations have been recorded in the past, there have been recent dips in numbers and with the recent bad weather we were unsure whether we would see any at all.

However, after an initial scare, we managed to find one at Warren House Gill…

My first sighting of a Durham brown argus! Resting nicely on a Bloody crane’s-bill.

A beautiful butterfly indeed. And much smaller than I had imagined.

I took a video which is not the greatest (due to the fact that nothing much happens!) but it is still nice to watch and hear the surrounding sounds while the butterfly rests with its wings upright, showing off its underside…


There were also many Common blue butterflies in the same location. I personally had never seen a blue butterfly before, so seeing some of them too was great. The male Common blues are unmistakeable…

Male Common blue

HOWEVER, the confusion begins with the female Common blue, which happens to be very similar to the Durham brown argus! This can make identifying both species a challenge, as to make certain it is one or the other, it takes a good close look.

A female Common blue

The best way to tell them apart is by looking at their undersides…

Durham brown argus underside

Its a case of looking at the spots! The forewing of the Durham brown argus has a collection of spots in the shape of a C, with one further spot in front of the C.

Female Common blue on my finger, showing underside

On the forewing of the Common blue however, there is again a C shape of spots, but with two spots in front!

There are other slight differences but I think this is the easiest way to tell these two species apart.

During the surveying we also came across a number of other species. We saw a handful of Wall brown butterflies basking in the sunshine, usually on bare patches of soil, a Small heath butterfly, and a Dingy skipper butterfly…

Dingy skipper

Plus one of my favourites – a Small copper butterfly…

Small copper

And also a tattered Painted lady butterfly…

Painted lady

The Painted lady is one of only a few butterflies that migrates to the UK. Every year, it takes on a mammoth migration north, up from the desert fringes of North Africa, the Middle East, and central Asia, to mainland Europe and on to Britain and Ireland. Amazing!

As well as the butterflies, we also saw a few day flying moths throughout the day. Two which we could identify were the butterfly-like Latticed heath moth and the attractive black Chimney sweeper moth, which led me on a long and unsuccessful chase up a steep bank to try and grab a photo of it.

Finally, I saw my first dragonfly of the year! A wonderful Broad-bodied chaser

Broad-bodied chaser dragonfly

————

Chris | National Trust

Chris | National Trust

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2 thoughts on “In search of the Durham brown argus

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