Sunday, 22 June 2008

Ustilago maydis

Always on the look out for something really weird, in 2006 I found this grotesque thing. The general impression is of a set of giant rotting teeth.

It didn't take much tracking down. Many fungi are host specific, so if you can tell what the fungus is growing on you stand a chance of identifying it. This rises to a good chance when the fungus is as distinctive as this. In this case the host was maize Zea mays and the fungus is maize smut Ustilago maydis. The fungus was growing on the cobs.

Though U. maydis is common in North America, it's very rare in the UK. This was only the ninth time that it had been recorded. It's unlikely to be overlooked, so it's probably genuinely rare. The field it was found in had Z. mays growing with other exotic grasses that had obviously been sown for game cover. As a result, I suspect that the field had not been sprayed with fungicides that would ordinarily prevent U. maydis from growing.

Apparently, in North America U. maydis has traditionally been, and is still considered by some, to be a good edible fungus. In fact I read that some cultures prize the fungus more than the sweetcorn. Would you eat this?

Saturday, 21 June 2008

I ♥ morphometrics

Put simply, morphometrics is 'measuring shapes'. In the normal, biological context this refers to the shape of study organisms. It is used by the taxonomist as a way of determining species boundaries.

Not long after I first encountered morphometrics I found myself working on tricky Lasius sp., which meant that I had to try to make sense of Seifert (1992). Seifert seems to be the Master of Morphometrics, in Europe at least, and the measurements and indices he uses are much more complicated than I had encountered up until that point. At first I really hated them. I couldn't understand why identification of Lasius needed to be so complicated - couldn't the species be better described and thus made easier to identify?

Over time morphometrics have grown on me and I've come to really appreciate them. I now even understand most of what Seifert does, though I will admit to being lost by some of the discriminants that he uses!

The most recent and one of the cleverest morphometric tools that I've encountered is from Seifert (2007), for separating the Formica picea/gagatoides/gagates group from the F. fusca/lemani group. I had already decided that the specimen that I was working on was F. fusca and knew that it definitely wasn't from the picea/gagatoides/gagates group, as these are all much shinier. However, in the couplet for separating the two groups I spotted an index that I had not encountered before: sqPDF.

Translating as best I can from the German, sqPDF is the square root of the distance between individual pubescence hairs within the triangle formed by the ocelli. PDF = l/n; where n = number of the pubescence hairs that intersect three transverse measuring lines of overall length l. The position of these measuring lines is shown in red in the picture below.

The thing that I found so intriguing about this is the pubescence hairs are extremely small, so I decided to see if I could make sqPDF work. I measured the length of the three lines combined to be 663µm and counted 68 hairs intersecting the three lines. This gave a PDF of 9.75µm, so the sqPDF was 3.12µm. This is within the range given for F. fusca/lemani (sqPDF 2.4-3.5µm) and outside of the range given for F. picea/gagatoides/gagates (spPDF 3.6-10.8µm), so the calculation worked!

This might seem like a lot of work, but it's not. Morphometrics are indisputable. I know from experience that you can get to the end of a key based on descriptions alone and be less than convinced that you've got the right answer. You then spend hours checking the other 'possibilities' had you taken different routes through the key. Morphometrics eliminate much of the doubt, give you a nice, neat, believable answer and ultimately save time.

If and when I finally write my first key, expect to see lots of numbers in the couplets!

Saturday, 14 June 2008

German ant collections

Another place visited; another list of ants collected. This time the area covered is a small part of Bavaria, as a result of a visit to the University of Regensburg. This list will develop over the next few weeks, as I have numerous specimens to look at. Once I have identified everthing I will send a full list of the records to the university and to any other interested parties.

It is possible to accurately identify some of the species listed in the field, so not all were actually collected. Some of them were collected by Marion Füßl, who found many species before I did and thus proved to be a very useful person to have around! Others were collected with a group of researchers from the university, who very kindly spent their public holiday showing me around. Yet more were collected by Christiane Wanke over the past few years and passed to me to identify.

Though I was not aiming specifically to collect rare species, the letters in red relate to species the German Red Data List (from: Seifert, 2007).

          quadripuntatus RLD3
          brunneus 1
          vindobonensis RLD2
          lobicornis RLD3
          schencki RLD3
          specioides RLD3
          fugax RLD3
          erraticum RLD3
          corticalis RLD2
          interruptus RLD3
          parvulus RLD3
          saxonicus RLD2
          tuberum RLD2

1 Colony found containing the myrmecophilous woodlouse Platyarthrus hoffmannseggi.

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

Thursday, 12 June 2008

Dr Peter Witt

In the 1950s and 60s Dr. Peter Witt made a number of studies on the effects of various drugs on orb-web spiders, particularly the visible effects that the drugs had on their webs.

I found out about this research when I was at college, but for a long time assumed that it was just an urban myth. However, there is now the following video, which explains what actually happened:

Tuesday, 10 June 2008

X Dactyloglossum mixtum

The British summer has finally arrived, which means my flat is hot. Really hot. Too hot to look down a microscope without everything steaming up. As a result all ant work has had to cease until it cools down1.

I thought that in the meantime I might present some photographs of other things. I have an online gallery that I kept running for about 3 years and then neglected, so I'm letting the subscription run out. The photos, including some interesting ones, will go with it, so I think it will be nice to save some of them by publishing them here.

X Dactyloglossum mixtum is the hybrid between frog orchid Coeloglossum viride and common spotted-orchid Dactylorhiza fuchsii. Other images can be found at the UK Hardy Orchid Society's website.

The parent species are both fairly common in the UK and their habitats overlap, so X Dactyloglossum mixtum is widespread, but uncommon and rarely found. This specimen was found near Cheltenham in Gloucestershire in 2004 and was only the fifth record for the county. However, the really interesting thing is that the last time it was recorded in Gloucestershire was on the same site in 1966, so it's easy to speculate that this could be a very old plant.

I've looked for this plant subsequently in the same place, but have not found it since. It is likely that, like most orchids, X Dactyloglossum mixtum flowers only sporadically.

Incidentally, recent work by Professor Richard Bateman and colleagues on a phylogeny of orchids based on DNA has shown that Coeloglossum viride is actually a Dactylorhiza. This means that a new combination needs to be published for the hybrid, which should make it Dactylorhiza x mixta.

I should acknowledge Simon Harrap for originally suggesting the identity, and Mark and Clare Kitchen, BSBI Vice County Recorders for Gloucestershire, for verifying the specimen.

1 Like most British properties, my flat does not have air conditioning. What it does have is a very large south-facing window.

Monday, 2 June 2008

Satellite fly

This is a new one for me - like a lot of people I didn't even know such things existed.

Last month I was surveying a site in Surrey, just outside of Greater London, and had found a nice south facing slope with a thermophilic invertebrate community present. This included mining bees Andrena sp., plus the cleptoparasitic nomad bees Nomada sp. and bee-flies Bombylius sp., and the wasp Dolichovespula media. Also present were the ants Formica fusca, so I spent a bit of time on my knees seeing what other species were present (only Lasius niger s. str. and Myrmica scabrinodis as it turned out).

Whilst I was on the ground a solitary bee flew by, followed closely by this fairly nondescript looking fly. The bee stopped, and the fly stopped a few centimetres behind. The bee flew a little further and stopped, and the fly did likewise. It slowly dawned on me that the fly was actually stalking the bee!

The bee started to move down amongst some grass whilst the fly waited around, so I took the opportunity to take the photographs below. Okay, so they will win no prizes, but they were the only two I could take before I got too close and scared the fly away.

It's taken me a while to work out what this thing was, but I'm now pretty certain it was a satellite fly Leucophora sp. Like Nomada and Bombylius, Leucophora are cleptoparasitic, laying their eggs in the burrows of the bees they hunt. According to the Society for the study of flies there are only eight species of Leucophora in the UK, none of which have been commonly recorded if their maps are any judge (though these are likely to be very incomplete).

However, other than this I've been unable to find out any information. Remarkably, none of the British species of Leucophora have conservation status, which implies that they were missed or ignored the last time these flies were reviewed, as some of the eight species must be rare. Perhaps too little was known about them to make an accurate judgement of their status. Honestly, if it hadn't been behaving so unusually I'd have ignored this individual.

If anyone else has any useful information on these beasts I'd be very interested to hear, even if it is to say that they are actually really common!