Easy to recognise aleocharines

This useful guide has been produced by Clive Washington

Brachyusa concolor 

So here we have number 1 in a series of Aleocharines which you can learn to recognise. This little beetle (2.2mm), which ordinarily might have you reaching for the Valium, is Brachyusa concolor. It's actually easy to identify when you notice it's unique characters. The head is quite transverse and the eyes take up most of the side of the head - almost like a Stenus. The hind edge of the pronotum is very sinuate, causing the hind corners to project considerably. The pubescence is so short you will have difficulty finding it. The first hind tarsomere is a little longer than the next 2 segments. In combination these characters get you the ID.

Nehemitropia lividipennis 

Here we have No. 2 in our series of Aleocharines that can be identified by direct recognition from photographs . This is the common Nehemitropia lividipennis. You will probably have noticed that several Athetines have pale brown diagonal streaks across the elytra to some extent. In Nehemitropia this is extremely pronounced so that they really stand out, the whole elytra can appear yellowish in some specimens. In addition, the shape of the pronotum is distinct - at the base it's nearly as wide as the elytra, and tapers forwards, looking rather similar to the pronotum in Oxypoda. You could possibly confuse this with Oxypoda - although these have the first hind tarsal segment significantly longer than the second, and the tergites have much finer, silky pubescence. Once you've seen one of these you won't confuse it with anything else, although you might want to dissect your first few to be sure. At 4mm it's an easy dissection, it's Fig 184 in Palm/Strand & Vik, who use the older name sordida.

Ocyusa maura

Here is no. 3 in our series of Aleocharines you should be able to recognise if you're sufficiently crazy to attempt it. Found this guy (sorry girl) at Risley Moss at the weekend, it's one of those that you might pass over as another M. fungi until you look closely. The key character here is the extremely rounded appearance of the pronotum and elytra, which look almost bulbous. Tarsi are 5,5,5 although the front are very difficult to count, which sent me off in the wrong direction at first. The hind angles of the elytra (which again are rounded downwards on the hind margin) are deeply emarginate. Pubescence is type 2. The bases of the antennae are pale, the rest darker. There are no marginal or tibial bristles. There is a small tooth on the right mandible, although it's too far down to see unless you can open the jaws wide, which is tricky with a specimen so small (2.2 mm). If you're one of those people who look for temple borders, then they are very strong in this species, and extend nearly to the front of the head underneath the eye. The first three visible tergites are deeply transversely impressed. This is Ocyusa maura. If you find one with the first four tergites impressed, it is probably O. picina, which I haven't seen yet.

Geostiba circellaris

No. 4 in recognisable Aleocharines. You need to know this one as it's the extremely common Geostiba circellaris. It stands out initially as it's rather long and pale, although this alone isn't sufficient to identify it. Note (1) the eyes are very small, less than a third of the length of the temples, (2) most of the pronotal pubescence lies backwards, (3) the rear edge of the pronotum is flattened in the centre and extends slightly over the elytra, which are shorter than the pronotum. This specimen is a male - it has two small raised areas on the elytra and a small keel on the 5th tergite. Length is 2.4mm although they do vary, I've found them quite a bit smaller. This one from Dibbinsdale Nature reserve, (VC58) 27th February 2019