Spider eyes and ID

I've recently returned from the expedition to Cuba. And guess what I did there... I held a tarantula. I'm very proud of this. I feel that spiders and I are now better friends. It wasn't ENORMOUS but it was a good handful. I liked it so much that I insisted on holding it three times. In the end it relaxed quietly in my palm while I casually spoke to people. So this new familiarity helped me the other day when Student A arrived to identify his specimens (any spider looks like tarantula under a microscope so it's best to be prepared).

Wolf spider by Thomas Shahan

We found the main dichotomous keys difficult. It would have been better if we could have turned to an expert arachnologist to explain what was being got at. But as lone neophytes we found the lateral key in the Aidgap spider families key the best place to start. To avoid tears you may want to do the same. After finding a likely family we then went to the Collins Guide.

I learned three important things. Firstly, that a pickled spider may be helpful because it's still, but otherwise it's an alive spider that can tell you many more useful things, and you should have written those things down when you found it. Identification will be greatly more likely if you can authoritatively say something about a spider's habitat, behaviour and web or lack thereof - all these things feature in the keys.

Secondly, that the arrangement of a spider's eyes is very useful in its identification, -  this would be a critical thing to observe and draw in your notebook.. The wolf spider above has two big headlight-style eyes at the front, two offset towards the back, and a curious row of four small eyes below - just like the wolf spider Student A found. Doubtless the big front eyes are an adaptation for seeking out prey. But what's going on with those four small eyes? I feel like i want to know more about spider eyes. I'm not sure that's something you hear every day. But do most people even know that most spiders have eight eyes?

Thirdly, it's very likely that you're only going to be able to get so far with the keys - distinguishing species usually comes down to very careful observation of the reproductive bits of adult spiders. That feels like pretty advanced stuff and on small specimens such things might be too difficult to see at all. I felt we could discount some options on grounds of habitat / geography / rareness instead. But often we were still left with a choice and it would have been dishonest to pick one over another. I think you need to make clear in your notebook your decision making process for either stopping at the Genus, or pressing on to a particular Species. Spiders just are difficult. I think the person marking your collection will have to acknowledge this.

Image by Hans Hillewaert

This is Dysdera crocata, the woodlouse-eating spider, one of A's finds. We were able to name it to species level because of its size - ours was female with a body of 15mm, so could only be the species crocata. This was a satisfying moment after all the previous pain. Dysdera has (apparently) only six eyes - they look like this:

Image by Patrick Moran.

We were also caught up in looking for cribellums and calamistrums - the lovely words of the new terminology amused me even if we had difficulty finding the things. I'm quite sure though that the more spiders I look at, the clearer all these things will become. It just takes effort and time. (Which is why you shouldn't leave things until late. This is very late in case you were wondering.)

If you want spider-related reading, I've just found  Rod Crawford's Spider Myths -  much for the new spider fan to enjoy, and much of it touches on the difficulties of identification. You can see all his arachnologist gear and read about his collecting exploits here, too. Or you may prefer the blog of the Spiderlord, who is based in the UK. He's pretty annoyed about our eight-legged friends being misrepresented in the media.