Sericoderus brevicornis

Sericoderus brevicornis

I found this indoors. At 1.15mm long it's not the easiest thing to see and photograph but considering the size the ID wasn't too troublesome.

male Sericoderus brevicornis showing showing metasternum, antenna and median lobe (2 views), North Elmham (Norfolk, UK), 21st August 2021

For a while I used a sticky pheremone lure trap indoors to try and catch Common Clothes Moths Tineola bisselliella. It was pretty useless - I think it might have attracted one or two close to it, but not actually on to it, and it also attracted different (harmless) Tineids in from outside. I found this beetle stuck to the trap one day, though whether it was attracted to the pheremone or just landed on it by chance is anyone's guess. At first I was almost convinced it only had 10 antennal segments which would make it a female, but contradicting this it clearly had what looked like a metasternal tubercle. At this point I hadn't seen a female so wasn't sure how smooth they were, so I dissected it to make sure. After soaking the whole insect in KOH the 11th segment of the antenna (well, the 3rd actually) became possible to see, and the aedeagus removed any question (shown here without isolating the median lobe).

male Sericoderus brevicornis showing showing metasternum, antennae (2 views) and aedeagus (2 views), North Elmham (Norfolk, UK), 21st August 2021

This was in a pheremone lure trap but with no lure set. I think it will have arrived accidentally rather than being drawn in my any residual pheremone from last time it was in use. The smoother metasternum meant it was a female so it needed to be dissected to examine the spermatheca. When I first looked at this I briefly flirted with the idea it might be lateralis as there seemed to be very little in the way of ducts emerging from the base of the gland duct lobe and there was no sign of the preapical constriction on the gland duct lobe. However closer inspection revealed that the apex of the lobe had been broken and wasn't complete. Although the ducts at the join of the lobe and the bulb seemed shorter and therefore less conspicuous than shown in Duff for brevicornis, there did seem to be two structures adjacent to one another here so if these were the sperm duct and the sperm duct lobe then it was brevicornis indeed. After soaking the abdomen in KOH the gentlest pressure on the abdomen caused a load of gunk to extrude through the anus (or at least an apical aperture) and the spermatheca had passed through with it getting stuck at the entrance. I suspect it became damaged here which made for a less satisfactory examination, but all things considered I'm reasonably happy it's another brevicornis.

female Sericoderus brevicornis showing showing underparts and spermatheca (2 views), North Elmham (Norfolk, UK), 6th September 2023