Small Birch Purple Eriocrania salopiella, collected from Kelling Heath by DN, 4th May
Like the last, this one shared the same external features including the broad wings, un-hair-like scales on the hindwing, antennae shorter than half the length of the forewing and pale yellow head hairs. But if this isn't enough to prove the ID, a closer examination is needed, preferably of a male.
Unfortunately this one proved to be another female. Identification of females may not be impossible, but more material and comparison with other species is really needed to fully confirm possible features. The things we're looking at are the sensoria on the sternites, or in layman terms, pairs of holes on the surface of certain segments of the abdomen, and also the very tip of the ovipositor.
Most Eriocrania have pairs of sensoria on two adjacent segments and the size, and relative size (and possibly also the shape) of these holes seems to be relevant. Both moths had a pair of large round holes on one segment and little or no holes on the adjacent segment. That seems to rule out several Eriocrania species and is probably supportive of salopiella, though there is little reference material out there for some species.
The ovipositor was hidden on the first moth so it required dissecting to access it, but on the second one it was protruding so not requiring a full dissection. Again lack of reference data demands caution but we can at least say that the form of the tip of the ovipositor of both Dave's moths was a perfect match to the tip of the ovipositor of Eriocrania salopiella that is shown at the Dissection Group.
Small Birch Purple Eriocrania salopiella (ovipositor), collected from Kelling Heath by DN, 28th April
Small Birch Purple Eriocrania salopiella (ovipositor tip protruding from abdomen), collected from Kelling Heath by DN, 4th May
Had some great discussion with Jon Clifton over this and many thanks to him for coming up with some good information and pointers. In conclusion everything seems to point to both moths being salopiella and while there is still more to learn about identifying females, Jon and Jim (county recorder) agree that the evidence for these two is sufficient to record them as salopiella.
For some reason - we don't know what - it seems that the majority of Eriocrania caught turn out to be females. That being so it seems worthwhile doing more work to work out robust ID features for females of this group.