Small Blue - Cupido minimus

In late May 2010 I headed down to a small site on the Scottish Borders coast where I had heard that there is a small colony of Small Blue butterflies, Cupido minimus. This is the UK's smallest butterfly which occurs mostly on the south coast of England but also has a few scattered colonies around the Scottish coast.
I was blessed with good weather and after an hour's drive and half an hour's walk I was rewarded with my first view of this beautiful little butterfly.

They really are small, about 18mm wingspan. The upper side of the wings is brown and the males have a scattering of blue scales. The underside is a pale grey with black dots and blue scales towards the base.
The site I found them in is only about 30 feet by 30 feet on a steep scree slope. The colony seems so vulnerable there.

I have since head that another colony has been found not too far away from this one, so it would be nice to think that they are expanding their range.

I returned again in May 2012 to see these lovely little butterflies and they were there again in good numbers. Depending on the weather the adults occur during May and June.

The food plant is kidney vetch, Anthyllis vulneraria, which likes alkaline conditions and seems to do well on cliffs and scree slopes. I imagine that it is easily out-competed by grasses and shrubs, so isn't a particularly common plant.

Eggs are laid on the flower heads and the caterpillars feed on the flower. This flower head has an egg on it.

The eggs are very small - less than a millimetre across.

I was involved with a survey to look for kidney vetch along the coast of Northumberland and the Scottish Borders. I found a few areas, but sadly no more butterflies. I have been told of some areas of kidney vetch in East Lothian, which I will have to check out.