The genus Phryxe contains a few common species (nemea, vulgaris & heraclei) and a few very rare ones (magnicornis & erythrostoma). The key pulls out nemea first by the wide gap between the facial-ridge bristles and the descending parafrontals – wider than the width of antenna-3 plus the mustardy/yellow frontal area. Splitting off heraclei has always been a matter of looking for extra bristles along the underside of costal wing section 2, which indicate heraclei – without this would mean moving on to magnicornis (split off using male genitalia), erythrostoma (big with long claws) & vulgaris (the rest). So it’s clear that male genitalia are important (once you get past nemea) but recently I have found several specimens that have vulgaris-type genitalia but which have the extra bristlets along wing section 2.
The first pair of photos shows a standard male Phryxe heraclei – the wing edge section has a scattering of extra bristlets on the underside of the vein between the leading edge and the wing membrane. The genitalia have very rounded surstyli and a smoothly rounded cercus:
The next photo shows the troublesome Phryxe vulgaris – the wing edge also has stray bristlets and the genitalia are of the usual vulgaris/nemea type with more elongate surstyli and a more angled cercus:
This means that once nemea has been excluded you really need to have a male specimen to prove vulgaris, magnicornis or heraclei. Phryxe erythrostoma is much larger and the claws are also quite distinctive. So, in summary:
1. The gap between the descending parafrontal bristles and the ascending facial ridge bristles is about as wide as the width of antenna-3 and the colour of the parafrontal region is a yellowish-grey … Phryxe nemea
– The gap narrower and the colour of the parafrontal dusting is more a blue-grey … other species
Male specimens: (continuing from above):
2. surstyli rounded and cerci smoothly curved underneath; underside of costal section 2 with 1 or more additional tiny bristlets along the vein between the continuous row of bristlets on the leading edge and the wing membrane … Phryxe heraclei
3. surstyli extremely narrow … Phryxe magnicornis
4. fore tarsal claws longer than the last tarsonomere [large species 8-10mm] … Phryxe erythrostoma
5. surstylus moderately elongate – between that of heraclei and magnicornis (as above) and cercus with a distinct angle to the underside … Phryxe vulgaris
In reality if you have a male and the genitalia look like nemea/vulgaris type then you just have to decide which species it is from the facial bristle gap and the colour of the dusting – you don’t have to progress to the other species.