Thursday, 31 January 2008

Camponotus rufoglaucus subsp. controversus

Camponotus rufoglaucus subsp. controversus is the second of the three species of Myrmosericus found in The Gambia. This is another ant that was by no means easy to identify.

It is clearly C. rufoglaucus because of the arrangement of the pubescence on the gaster, the smoothly rounded propodeum and the very compressed tibia (visible in the bottom picture). However, C. rufoglaucus sens. str. is an Indian species; in Africa there are at least seven subspecies. The two Gambian collections were identified as C. rufoglaucus subsp. controversus from type descriptions, since the tibia are clearly compressed, the head and mesosoma are entirely red, and the legs are black.

I also found some specimens labelled as C. rufoglaucus subsp. controversus in the London Natural History Museum, though not types and majors only. These specimens had a greater number of setae all over and pubescence on the gaster that was not as divergent, but identical colouration. However, as these were not types and the pubescence on the gaster was different from the type description I'm not convinced that they were identified accurately.

I also checked some of the many C. rufoglaucus sens. str. specimens in the museum collection. These were clearly not the same as my specimens (the Indian and Ugandan specimens in the museum collection were also not the same as each other), and again had less divergent pubescence on the gaster.

C. rufoglaucus subsp. controversus had been previously recorded from Tanzania, Zaire and Angola, so these Gambian collections represent a north-west range extension. They were collected only in Kololi as single workers on the sandy ground; no colonies were located.

Saturday, 26 January 2008

Camponotus olivieri

Camponotus olivieri is a widespread species in Africa, ranging from South Africa north to Sudan and west to Ghana. However, it is made up of a great many subspecies that probably deserve species status, so the situation may be rather more complicated than it seems at first.

Two subspecies of C. olivieri were collected in The Gambia: lemma and delagoensis. They differ quite markedly in pubescence and also, to a lesser extent, morphology. What I think provides some evidence that they deserve separate status is that they were both found at one site.

C. olivieri subsp. lemma was found in two locations: Abuko National Park, Lamin and Bijilo Forest Park, Kololi. In both cases it was found only on the ground. It can be distinguished from other species of C. olivieri by the rust colour at the base of the antennal scapes and the gaster, which is uniformly shiny, sparsely pubescent but still more densely pubescent than the mesosoma and has erect hairs that are thicker than the pubescence.

C. olivieri subsp. delagoensis was found at Abuko National Park, on a tree. It is similar to subsp. lemma, but has denser, yellow pubescence, especially on the gaster.

Both ants have been recorded only rarely, possibly due to the fact that they are regarded as subspecies and so have been more frequently recorded at species level. C. olivieri subsp. lemma had been recorded in Angola, Tanzania and former Zaire. C. olivieri subsp. delagoensis was only known from the type location at Delagoa Bay in Mozambique. This makes these Gambian records an extension of the known range of the species and both subspecies, especially large in the case of subsp. delagoensis.

These have both been compared with the type specimens from the Muséum d'histoire naturelle, Genève and the Naturhistorisches Museum Basel. This allowed me to confirm C. olivieri subsp. delagoenisis.

The syntypes of C. olivieri subsp. lemma are rather variably hairy, so much so that I wondered if Forel had mounted specimens from different colonies on the same pins. The main difference between these and my specimens was that most of the types were much less hairy, though one was similar to mine. It could be that the specimens have lost some of their pilosity. Regardless, I feel I need to do some more work to confirm that there is nothing closer.

Sunday, 20 January 2008

Unusual petiole shape in Lasius umbratus

In my last post I mentioned photographs of a queen ant that were posted to the BWARS discussion group. I asked the collector to send the specimen so that it could be identified properly and I've now had the opportunity to look at it.

It is a Lasius umbratus queen, which was correctly guessed by Andrew Jarman (my guess wasn't even in the right genus). The L. umbratus group is difficult, so I worked the specimen through a number of keys, but it was the head measurements in Seifert (1988) that gave the least ambiguous answer.

The petiole, the interesting thing about this specimen, is as unusual as it appeared in the original photographs taken by Claes-Göran Magnusson. So as to give a clearer impression I've taken some images of my own. The petiole in L. umbratus usually is emarginate, but it can be seen from these photographs that the emargination is much deeper, almost to the level of the anterior peduncle.

Wednesday, 2 January 2008


The latter few months of 2007 seemed bring encounters with an unusual number of freak ant specimens, unfortunately none of which were collected by me.

First, an ant with a third eye, a Myrmica as I recall, was brought to the BWARS workshops in September. At least, it appeared to be like a third eye. It was a black area that was partially buried in the cuticle of the head, but where it came to the surface it did have a bobbly appearance like that of a compound eye.

The ant presumably used the eye for seeing into the future.

Then before Christmas I looked properly at a specimen lent to me by Cedric Collingwood some months ago. He knew that I was working on the ants of The Gambia and had a few specimens in his collection. This specimen had been collected by Nicolas Blacker and identified by Cedric as Camponotus vividus, but it was unlike any of the specimens I had collected. I finally got around to identifying all the Camponotus I collected in the Gambia and discovered that I did have C. vividus, so needed to check why Cedric's were different. To my surprise I discovered that the specimen is actually a pseudogyne (between a queen and a worker). It is larger, paler and more matt, with a more developed mesosoma and one pair of barely developed tiny 'wings'. It may be the only pseudogyne of that species in any collection.

Finally, right at the end of 2007, C-G Magnusson posted some photos of an ant for ID to the BWARS discussion group. It was agreed that it looked most like a queen of a Camponotus... or a Lasius, but it had a very unusual shaped petiole, being so deeply emarginate that it had two erect blunt spines there instead.