Olibrus affinis

The Olibrus that I've found most often at the Cathedral Meadows is corticalis, and, partly because of that and partly because under the microscope this insect looked paler than it did in life, I was expecting this to be another corticalis. But despite my best efforts I couldn't see the microsculpture on most of the elytra, and I was pretty sure I didn't find it that hard to see on previous corticalis. There was some sinuous linear microsculpture towards the apex especially near the suture, as is described for affinis (and a couple of other species). The aedeagus clinched it for me, and it was only then that I realised that I had in fact recorded affinis at this location previously. The species is associated with Goat's-beard, Catsear and Smooth Catsear, the first two of which grow at this location, but this one was found on a Dandelion flower.

male Olibrus affinis showing its elytra (twoards the apex, suture side), aedeagus (side view and flat, latter with internal part to left), North Elmham Cathedral Meadows (Norfolk, UK), 4th June 2021

The previous one was a female. There are differences between the species in female genitalia, but these are quite subtle.

female Olibrus affinis showing its ovipositor, North Elmham Cathedral Meadows (Norfolk, UK), 7th August 2019

I labelled this one incorrectly at the time, but I'm not sure if I misidentified it or just got it mixed up with something else. Anyway, the photo of the genitalia appear to confirm that it should have been labelled as affinis.

male Olibrus affinis showing aedeagus (flat and side views), North Elmham Cathedral Meadows (Norfolk, UK), 19th August 2020

This female was found by suction. Duff shows the ovipositor gonocoxae for the whole genus but the differences between some species are not clear to me. This was identified as affinis using Duff's key - the gonocoxa seems to be consistent with affinis but also some other species.

female Olibrus affinis showing prosternum, metasternum and tip of ovipositor with close-up of gonocoxa, Wendling Beck Environment Project (Norfolk, UK), 30th July 2025

This was one of a hatrick of Olibrus found together by suction (the others being liquidus and aeneus). I keyed it to affinis using Duff and confirmed it with reference to the genitalia.

male Olibrus affinis showing apex of elytra, prosternum, metasternum and aedeagus (side and flat views), Wendling Beck Environment Project (Norfolk, UK), 25th August 2025