One simply does not walk into mordellids

Mordellids are fiddly little bastards. They're not called tumbling flower beetles for nothing. Tumbling being the operative word. Even after death they continue to be problematic. 

First problem is how to card them? On their side or on their front? Their hind legs have a nasty habit or remaining firmly tucked under their chin and the curved-shape of the abdomen makes standard carding a zen-like action that needs the patience and skill of a saint.

I also find some of them awfully tough to get to species. This one from June was a good case in point.

Note hind legs conveniently lodged under head!

I used the new mordellid key in Duff BBI vol 3.  It's obviously in the genus Mordellistena and as it has two spurs on the end of the hind tibia it is also in the subgenus Mordellistena. 

The next couplet looks at the shape of the 4th antennomere. Is it as long and broad as number 5 and the following ones or is it narrower and shorter. This one is definitely in the former camp. This narrows it to 3 species M. variegata, neuwaldeggiana and humeralis. The obliquely set lateral ridges on hind tibia (see above photo) eliminates variegata.

So we're left with either neuwaldeggiana or humeralis. First difference should be in the shape of the eye, with neuwaldeggiana showing a clear emargination where the antenna inserts into the head. That would seem to be pretty clear in this individual.  

The shape of the end of the 4th fore-tarsal segment also suggests neuwaldeggiana. 

So this seemed all straightforward, however, other guides and keys made me doubt this a bit. Luckily a post on Facebook got this from Mark Telfer "all-pale body and uniformly pale antennae, also relatively long 3rd ant segment" make this neuwaldeggiana.

So that's good to get a firm ID. It's also the 697th species of beetle I've found and ID'd in the UK. I wonder what the 700th will be......