Wednesday, 18 December 2013

A stab in the dark

Last Friday, I finished the first draft of my proposal. It's totally rough around the edges, but the bulk of it is there and I'm waiting on comments. I'd been putting off collecting, mainly because it is a major distraction from writing. But on Monday night I went out with my advisor and another guy who was really into spiders and knew where we could find some Cantuaria dendyi.

Finding lidded Cantuaria burrows is hard. Essentially, you are trying to find a particularly neat patch of soil, around a centimetre across (for the adults). To me it seems worse than looking for a needle in a hay stack - more like looking for a piece of hay that is ever so slightly more orangey than the rest of the haystack. However, apparently you get better with experience; the two guys found most of the burrows, but they would point at a patch of soil and say "There's one!" and I would be looking for ages before I saw the neat little hint of a lid. You have to hand it to these spiders - they are good at being invisible.

After we'd marked a few burrows with sticks, we waited for nightfall. In the dark, trapdoor spiders move to the tops of their burrows and wait beneath the lid for something crunchy to walk by. Tiny prey legs trigger the tripwires laid around the entrance of a burrow. A piece of grass drawn gently over the tripwires brings the spider out a little way, but to get them to come further I tied a piece of thread around a beetle (between the thorax and abdomen) and held onto the loose end. Under a red light (which spiders cannot see by), the beetle would stumble idiotically towards the lid of the burrow. The lid would twitch, fluffy spider toes would flick out, then eventually the bulk of the spider would lunge forward and grab the beetle, wrapping the front two pairs of legs around until the unfortunate prey disappeared. At the same instant, someone would thrust a trowel into the ground behind the entrance to the burrow. You have to be quick - they can go backwards at an incredible speed.

We collected four spiders. The next day I put one in a beaker and showed her around to pretty much everyone in the department (probably even some people I had never met before. In hindsight I may have come over a little crazy). She looked impressive, at least 2.5 cm long, hurtling around the beaker. I put some soil in buckets and poked holes for the spiders with a pen, and three went in easily. But the one that I had been messing with was not happy. When mygalomorphs (ancient spiders, like trapdoors and tarantulas) are really annoyed, they raise their front pairs of legs and expose the underside of their prosoma (the front half of the spider). If you continue to annoy them, they will usually bite. This one not only bit the tweezers I was using to usher her into her hole, she wrapped her whole body around them. I poked her abdomen to make her go forward but instead she spun around in an instant and went into the warning stance again. For an animal that never walks more than a metre, they are extremely fast.

Finally she went into her hole. They were all out of their holes this morning, but I expect they will settle down. One of them I have retrieved to give to my advisor, but the others I will keep for a while to see what they do.

I saw clusters of tiny, pebble-like mites on two of the spiders we collected. They will be useful for my project, as I would like to see if they evolve along similar patterns as the spiders they inhabit. I seem to have been targeted by parasites as well - since Monday night I have had big welts on my fingers that itch like hell. One of the disadvantages of mucking about with foliage at night, I guess.

No comments:

Post a Comment