We've come to f**k you over

I found this staph in my compost heap back in March and at the time was pleased to find that I could ID it to genus level in the field. This is one of the Aleochara. Of all the aleoch groups these are probably the easiest but as I was about to find out they still have the propensity to mess with your head and make you doubt your sanity.

There's a good key to these by Colin Welch that appeared in the Coleopterist many moons ago and is available to freely download here.

First couplet is easy, does the beetle have a two irregular rows of punctures (with hairs) on the pronotum either side of a smooth middle bit?

Bingo, this most obviously does putting this firmly in the subgenus Coprochara.

That helpfully narrows this to four species: bilineata, binotata, bipustulata and bi verna. 😉

The next bit is all about the colouring of the elytra. The fact that this has discreet orangey patches excludes bilineata  and binotata and leave us with this being either verna or bipustulata

As this was a male I whipped out its bits to have a look. The drawings in Welch looked different enough to me.

5A and B is A. bipustulata and 6A and B is A. verna

Firstly looking at a lateral view, i tried to ascertain the shape of the aedeagus which I've drawn in red in the image. Comparing to the illustration I was convinced I was looking at A. verna. It was then pointed out that the neck of the aedeagus was too thing for verna and was more akin to bipustulata.

So what about the dorsal view? Again to me it looks more like the illustration of verna, with a wider base and more 'light bulb' appearance.

Time to look at some other sources, first up the Swedish guide by Palm. The shape of the my beetle's aedeagus is perhaps a better match for bipustulata but on these the thickness  of aedeagus neck seems to be reversed with verna having the thinner neck!

Dorsal images of verna are here and there also drawings and photos at coleo.net. I think it's clear to see some confusion and possible variation in the aedeagus of this genus and in fact there is some suggestion that females are easier and the spermatheca are a better way to tell these apart.

One thing that appears to be consistently different is the the extent of the red/orange patch on the elytra.

Bipustulata has larger patches that cover almost a quarter of the elytra, verna are more concentrated on the inner corners of each elytra below. This is illustrated below.

Aleochara bipustulata (left) and A. verna (right)

So my beetle has quite large patches which would suggest that it is a male A. bipustulata. This is also the more common of the two species. Not easy though and a valuable learning experience. 

The post title comes from early 90s industrial super group Murder Inc. Saw them live in 92 supporting the Sisters of Mercy, they were very loud!