Comma in a Cornfield

I found this comma sunning itself on the edge of a field of ripening wheat yesterday. It's a common enough butterfly now in Durham but twenty years ago it was still a rare sight here. As recently as 1986 T.C.Dunn and J.D. Parrack wrote in their Moths and Butterflies of Northumberland and Durham that occasional specimens that were reported were "...only strays and cannot yet be thought of as recolonising the north-east, although there is recent evidence of some range expansion in the Midlands. They are, however, an indication that they do arrive here sometimes and if the wandering habit were to become more frequent as during a time of expansion, it could take up residence here once more". The authors would be delighted, I sure, to know that their predictions proved to be spot-on. The species went into a decline nationally in the late nineteenth and early twentieth century, when it was restricted to the Welsh Borders and South East England, but over the last few decades it's undergone a rapid range expansion. No one seems certain why this has come about, although there are suspicions that this is now a different race of butterfly than that which was common 200 years ago, with caterpillars that now feed on nettles rather than the much less common hops. Climate change might have asisted its northwards range expansion too.

This specimen looks like an example of the paler form from the first, July, brood known as form hutchinsonii, which will mate and produce a second brood in late August. The larger, darker form in the July brood merely feeds without mating and enters hibernation along with the second brood hutchinsonii progeny.