Fairly regularly something comes along and completely stumps me, but it doesn't normally happen with European ants.
I thought I knew Myrmica well, especially M. scabrinodis, which is one of the species I most regularly encounter. This Bavarian specimen really has caused me to do a disproportionate amount of work to resolve it's identity.
First of all I wasn't even 100% certain that it was a Myrmica. It has unusually large mandibles and, particularly, it appears to be covered with rather strange clavate hairs. I had to get my BIG eyepieces out to check the tibial spurs on the middle and hind legs (which were dubiously pectinate) and then count the palp segments, which always takes a lot of effort to get the position and lighting good enough to see anything. The result was that it is definitely a Myrmica.
By this stage I had already decided that it had the antennal scape and overall shape of M. scabrinodis, but those hairs were peculiar. I worked my mounted specimen through Seifert (1988) and his new book (2007), both of which suggested clearly that the specimen is M. scabrinodis1.
I then really started asking questions about those hairs and, once I had thought of fungi as a possibility, I quickly found was seems to be the most likely answer: Rickia wasmannii. This was described from Germany, though I've no idea how common recorded it is. It was only recently collected from Hungary and Romania (Tartally, et al, 2007), and does not appear to be known from the UK. All five specimens in this collection are covered in these little growths on almost every part of their bodies.
I haven't actually confirmed this, but I suspect that species of Rickia are host specific and that R. wasmannii is the only one that is known from Myrmica sp. However, if anyone has any additional information on Rickia sp. I'd be very grateful to hear about it. In the meantime I will spend a lot more time looking at British Myrmica in the hope that I can get the first UK record of R. wasmannii!
I sure know how to have fun on a Friday evening.
1 For those who are interested in such things, the standard measurements and indices used to make the identification were as follows:
Head length (HL) = 996 µm
Head width (HW) = 952 µm
HL/HW = 1.047
Scape length (SL) = 763 µm
SL/HL = 0.767
Minimum distance between frontal carinae (FR) = 310 µm
HW/FR = 3.071
Maximum distance between frontal lobes (FL) = 443 µm
FL/FR = 1.428
Length of propodeal spines (SP) = 310 µm
SP/HW = 0.311
Petiole width (PE) = 266 µm
PE/HW = 0.279
Postpetiole width (PP) = 376 µm
PP/HW = 0.395