Both these moths are Common Swifts. I caught the all-dark one the other day and wondered what it was, but there is a melanistic form which is about the same colour as a Common Swift, the bird. The females apparently also tend to be duller than the males, which I suppose is what you see on the right. These moths fly in May-June, their caterpillars living the rest of the year underground nibbling the roots of grasses.