Friday, 13 June 2008

Rickia wasmannii

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


Jochen Bihn said...

Nice find. Good luck with first record for the UK.

Sifolinia said...

Hmm. I've just been looking through Pontin (2005) The ants of Surrey. Plate 8 shows a picture of 'M. sabuleti with unusually shaped hairs' which look suspiciously like this.

balint said...

We are right now studying the presence of this fungi in two Romanian populations (those reported by Andras Tartally). Its prevalence is extremely high among M. scabrinodis. Also it seems to be associated only with this species, nevertheless other Myrmicas are present in the same type of habitats (wet).