Scotch Argus

[David M]

My brain is entering shutdown mode as winter approaches, and that means there's space for irrational thoughts that wouldn't normally circulate in my head during the butterfly season.

With next year's planned trip to France foremost in my mind, I've been spending time lately reading Tristan Lafranchis's guide to butterflies in France, which provides distribution maps for all French species.

Scotch Argus is present pretty much throughout the whole of the middle and eastern part of France from the far north to the far south. I suspect it's absent from the west because this is essentially a lowland region.

So, if there is no bias between north and south in France, why does this butterfly only occur extensively in Scotland and in a tiny number of places in northern England? After all, Snowdonia would be perfect for it as would the 600-800m mountains in south Wales, not to mention the elevated areas of south west England.

[Matsukaze]

The European distribution is very 'continental', avoiding areas with high rainfall and relatively warm winter temperatures (which begs the question of what it is doing in those parts of Argyll where just these conditions prevail).

[David M]

The European distribution is very 'continental', avoiding areas with high rainfall and relatively warm winter temperatures (which begs the question of what it is doing in those parts of Argyll where just these conditions prevail).

Indeed. The wintering grounds of many birds are found off the west coast of Britain, meaning that one has to conclude that the climate here is far milder than it is in continental Europe.

In fact, I spent an entire winter living and working in Oban 20 years ago and we barely had a frost!!

[essexbuzzard]

Hi there,
On the face of it there would seem to an abundance of habitat for scotch Argus in south Wales,as well as Cornwall and Devon. But i don't know how common the caterpillar food plant,blue moor grass,is there. There are also question marks over the mild,wet winter conditions here.
On the Continent,a much greater range of foodplants seem to be used,and adults are common on warm dry hillsides,in contrast to sites used in G.B.
But i would welcome other opinions on this.
Regards, Mark.

[millerd]

Did I read somewhere that they are found amongst sand dunes on the Belgian coast near Ostend?

I could have dreamt that one, I suppose...

Dave

[The Annoying Czech]

The Central European's optimum are recently localities with a well-preserved structure of biotopes providing various levels of succession varying from "naked ground" to "almost wood". Altitude's not that relevant, but sadly, many other small but complicated things yes, eg. solitary trees of certain age/height. And two factors endangers them greatly:

• Argus naturally survived first in areas with preserved small-scale farming. But unhappily in places that are often abandoned as first (turning into a wood very soon, especially when the bloody common spruce is present).

• Argus is not as strong umbrella species as Large Blue. So, prospering LB = vanishing Argus (or vice versa, but LB has a definite priority in the Czech Rep.). I visited a seemingly miraculous bitope with Argus, Large Blue and Niobe Fritillary temporarily prospering together in 08/2011. But from a long-term point of view, it's a big fake. Either Argus or LB & NF colonies are going to die sooner or later, the requirements are too strict/different.

Historically, this is nothing but an alternate solution after the open forests (that are obviously gone).

I hope this helps a bit.