August 16, 2010:
In brief sunny spells today a small number of Holly Blues (Celastrina argiolus) were flying. This is a site where I have seen them in the past and sometimes also earlier in the season when their larval food-plant is holly. By the month of August any of those flying are of the second generation and, perhaps strangely, the preferred food-plant now becomes ivy. Such behaviour is unknown in other British butterflies.
Here, males and females were associated with a short 50-metre stretch of sheltered, ivy-covered wall but unless it was warm and sunny they only settled briefly. Sometimes they would disappear from the site for long periods but would eventually return when the sun came out.
[Male, both above]
The female differs from the male in having a dark grey border to the upperside of the forewing; in the male this is restricted to just a very narrow band. In the second generation female (as here) these dark markings become more extensive and can extend inwards from the wing edge. In exceptional years there may even be a third generation.
[Warm ivy-covered wall near Silverdale]