Bee male (Andrena) which doesn't fit the key

[Richard Dickson]

This male Andrena about 10.5 mm long came from maple blossom at Denny Wood in New Forest SU3306 on 25th April 2011, and there were others the same. It looks a bit like A. dorsata. In Fauna Helvetica Apidae 6 it keys fairly comfortably to couplet 255, but then the problems begin. The size is intermediate, and the 3rd antennal segment is rather over half the length of the 4th. The sculpture of tergite 1 and tergite 2 does not match that of A. dorsata, and critically, the genitalia do not match any shown in Apidae 6, posessing pointed posterior projections to the gonocoxites and very broad gonostyles which are slightly concave externally and slightly emarginate internally.

[Jason Green]

Welcome to WAB, Richard!

I can't help with the ID; I find males hard enough! Nice image showing the split-textures on the tergal discs. A couple of other points though - firstly, does SM2 look unusually small? I doubt an important point, but I can't see that in any of my specimens. Oh, and a great setting, how do you manage to extrude the GC like that? I find it fairly easy with Cheilosia, but can't imagine the same with Hymenoptera. Do tell!

Nice to see you on WAB.

[Richard Dickson]

Thank you for pointing that out: the 2nd submarginal cell is indeed narrower than in any other Andrena I've just looked at. That made me wonder if it was actually an Andrena at all - but everything else is right.
I've no special curatorial secrets. I don't have trouble extruding the genitalia of Cheilosia sp., but I have a great deal of difficulty interpreting what I see! Bee genitalia are a model of simplicity by comparison.
This bee may well be something very common, but I was surprised by the distinctive genitalia - not a feature you expect in Andrena. We wait and see!

[Matt Smith]

From the genitalia, I would suggest Andrena haemorrhoa, the "pointy bits" are fairly distinctive. The antennae characters match as well, in A.haemorrhoa segment 3 is noticeably shorter then 4. Check for the "A.haemorrhoa ridge/carina" across the rear of the propodeum, it can be easy to miss amongst all the hair.

Extracting the genital capsule is easy if the specimen is fresh. I either use a fine ento pin with the tip bent to make a "hook" to pull out the gapsule, of just open the end of the abdomen and grasp the capsule with a pair of very fine tweezers. Once it is extended it normall stays in place without too many problems.

[Richard Dickson]

Thank you for responding, Matt. I've compared the genitalia of these with a known male A. haemorrhoa and you're right: they match.
I'm not surprised I missed this character in the key. It is far less evident than in the female. There is an abrupt transition from costulae running down the dorsal face of the propodeum (=metapostnotum) to the rugose surface of the declivity and to the lateral faces, but only rudiments of a ridge/carina. I shall be more careful in future. I wasted an aweful lot of time trying to sort this one out! I very much appreciate your help.