Lesser Common Rustic Mesapamea didyma
Wingspan 22-30 mm.
Almost identical in appearance to Common Rustic, the two species (and M. remmi, Remm's Rustic) can only be reliably separated by examination of the genitalia.
The species has been found to be fairly common and widespread throughout much of the British Isles, although information about its true distribution is still developing.
The adults fly in a single generation in July and August, and the larvae feed on various grasses, including cock's-foot (Dactylis glomerata).
The male genitalia plates depicted demonstrate the differences in the structure of the cornutus of the male aedeagus. In secalis, the cornutus is blunt ended and joined to the membrane for the whole length, whereas in didyma, it is more pointed, and joined to the membrane only for a small part of its length.