Stenocranus fuscovittatus

The Stenocranus species are rather tricky to identify. Firstly one of the key characters separating the commonest minutus from the one I see most major and this one is the colour of the dark stripes on the face - brownish on minutus and black on the other two - but what when it seems to be really dark brown so blackish that you have to look really closely to see the hint of brown, and what when you're looking at a specimen under the microscope and it looks clearly black but it looks brown in the photos of the insect you took when it was alive...? Both are problems I've experienced with this group, and I always identify using a combination of that and the length of the vertex - which can also be quite tricky to interpret.

This individual was caught at the same site as a Stenocranus major. The latter was swept from an area that had Reed Canary-grass growing (major is associated with Reed Canary-grass) and this fuscovittatus, a first for me, was swept from sedges. This provided me with an opportunity to compare the two side-by-side which helped give me confidence in what wasn't the easiest identification. Both insects had black or at least blackish facial marks suggesting neither were minutus. There was a significant size difference between the two - the major being 6.4mm long and this one being 5.4mm long. The major had a longer vertex than this one - major is in between minutus and fuscovittatus in this respect and when identifying major I often find it difficult to decide if they're better for major or minutus on vertex length. No such problems with this one on which the vertex was clearly short, and this was especially obvious when placed next to the major.

This individual showed several darkened veins towards the wing tip (and a darker apical cell), which I don't recall seeing on the other Stenocranus before, and compared directly with this major the stripes on the legs and frons were thicker - but I don't know if that's just down to individual variation or if it's relevant to the identification. This fuscovittatus showed asymmetrical venation with the external apical vein forked on one wing but not on the other.

Stenocranus fuscovittatus (with Stenocranus major in last 3 photos), Gressenhall (Norfolk, UK), 25th April 2022