Here is a series of pictures of a couple of butterflies from last August. I suspected this was some sort of mating related activity, but I wasn't sure what exactly was going on. I e-mailed the pictures to Torben Larsen (whose book on butterfly collecting I reviewed here) and asked for his help. Torben kindly provided his opinion.
He thought that the male, the one in the air, was attempting to mate with the female on the flower. The female, however, appears to have been reluctant. Torben indicated that the purpose of the raised abdomen of the female was to physically prevent the male from mating if it succeeded in landing next to the female.
I also wasn't sure what the species was. I have difficulty telling these sulphurs apart. My choices were either Colias philodice or C. eurytheme. Torben's pick was C. eurytheme.
It will be another couple of months before we start seeing butterflies here in Maryland (they are predicting snow for tomorrow). But Firefly Forest Blog tells us that down in Arizona Great Purple Hairstreak (Atlides halesus) is already out.