Monday, 5 November 2007

Pachycondyla sennaarensis

Pachycondyla sennaarensis is probably one of the most common ant species in the coastal region of The Gambia, as I collected it 10 times. I also got to know it over the week that I was there and had soon started to ignore the many lone workers that I frequently saw.

Remarkably, given how common it is in the area that other myrmecologists were most likely to visit, it hadn't been recorded from The Gambia before. I'd be tempted to suggest that it might have spread into the country since the early 20th century, when the last myrmecologists visited, but it was recorded in Senegal at about that time. Perhaps it's just been more successful than other ants as the area has been developed.

It seemed equally happy around buildings and in natural areas, where it nested directly in the ground, often in cracks in concrete. It was described by Dejean & Lachaud (1994) as being at least partially seed eating, which is extremely unusual for a ponerine ant. My observations agree with this, as the refuse piles around nest entrances often contained seed husks and other vegetable matter.

They also showed the kind of wear on their teeth that other seed eaters, such as Messor, tend to develop on older workers. Rather typically, it proved impossible to get a decent photograph of the one specimen that showed really distinctive wear. I hope that the photos below give some indication of what I mean, despite the fact that they both chose to die chewing on their own legs.

The first one shows little wear:

Whilst the second shows slightly more (note particularly the tooth on the right just above the leg):

Perhaps you'll just have to take my word for it.

I also found a queen. This was washed up on the shore on the part of Jinack Island that is within Senegal, though it probably washed down the river Gambia to get there, as it was already dead. Despite the fact that it was not found in a colony, it has been possible to identify it as P. sennaarensis with some confidence, as none of the defining features are on the mesosoma and so are presumably the same on the queen as the worker.

This species also stings. I discovered this on my first day in The Gambia when, in my rush to get out and explore, I left my forceps and pooter in my case in the hotel. Picking up these with your fingers is perhaps not to be recommended! In terms pain, it wasn't actually too bad initially (I've been stung by worse), perhaps rating as a 2.5 on the Schmitt Sting Pain Index (just above a European honey bee). However, after 20 or so my thumb, in particular, was starting to feel a bit numb, so I decided to stop. For the next 3 days the skin on my thumb and forefinger, which had taken the bulk of the punishment, slowly peeled away.

All good fun.

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