Friday arachnid blogging; or, The Body of an American

While in America last summer I saw a number of spiders, many of them unfamiliar to me. One of them was this impressive jumping spider:

Her jumping days, alas, are over. I killed her with kindness, and I bitterly regret it. Now, I've killed a lot of spiders in my day, and don't regret doing so at all. When I collect a spider, I kill it quickly in alcohol (which is also what the specimens are stored in; you cannot pin a spider to a card as you would an insect). I don't much like the fact that they die, but I do not feel bad about killing them so that I can later study them.

But my daughter was with me the day we found this spider (in New York, BTW). She loves nature in general and spiders in particular, but is unhappy to see them dropped into alcohol, and she successfully pleaded for this one's life. Okay, I thought, I'll just immobilise her for a bit (the spider, not my daughter) so I can take some close-up photos, then set her on her merry jumping way. Spiders being cold-blooded creatures, you can make them groggy by making them cold. So I put her into a freezer for a few minutes. Then out into to the sunlight for the photo op, and I fully expected that, as she warmed up, she'd stretch her legs, yawn, and scuttle off. It was not to be; she was fated to hold that pose forever. As I said, it doesn't bother me to kill a spider that I mean to collect; but it bothers me quite a bit to have killed through stupidity one that I meant to release. Next time I'll use the refrigerator instead.

But there remained the question: what sort of jumping spider was she? I had never seen anything like her.

For one thing, she was (by jumping spider standards) huge. Most are tiny to midrange, but she was immense. (Relatively speaking; she could still sit comfortably on your thumbnail.) And, though she was for the most part dark and dull, look at those amazing metallic chelicerae!

When you want to identify a spider (or other animal) you've never seen before, what you do is sit down with a dichotomous key. If you've never seen one of these, they work a bit like those 'Choose Your Own Adventure!' books. Only, instead of working your way towards an ending, happy or otherwise, you are working your way towards the taxon to which your specimen belongs. Here's a simplified example:

   Eight legs, two main body parts, fangs ......... 1
   Other................................................. 2

If you go to 1, you will be presented with another series of dichotomies that you can follow, ideally, all the way down to Spiderus ickyus, or whatever. (Or, if your specimen didn't match the description for 1, you'd go to 2, and follow the chain of dichotomies there, until you eventually learn that your specimen is a vampire bat, or a sea-slug, or a blue whale.)

Now, determining a jumping spider can be a daunting thing. The Salticidae, as they are formally known, are a species-rich family. Indeed, there is none richer in the spider world. At last count (according to Norman Platnick's World Spider Catalog) there were 5,001 species of salticids, in 544 genera. Still, given my spider's large size and gleaming 'jaws', I'd hoped the narrowing-down would go quickly.

It didn't. In fact, it didn't go anywhere at all. The key I usually use, Spinnen Mitteleuropas, is excellent (there's even an online version). 'Mitteleuropa' means something different in spidering terms than it does politically, but still, it's a reasonably big swath of land. And nowhere in it, it seems, does my spider exist. A somewhat less systematically rigourous web search (looking for references like 'metallic fangs' and 'big') soon suggested, though, that my spider belongs to the salticid genus Phidippus. And a look at some salticid websites soon turned up pictures that confirmed as much. (P. audax seems a likely candidate.)

Here's the thing, though: Phidippus is an American spider genus. According to Platnick, its species are found in North and South America, with the overwhelming majority north of the Panama canal; indeed, most are in the United States. (Platnick also lists a few species on the Indian subcontinent, but notes that these are probably misplaced in the genus.)

Wayne Maddison, who contributed the salticid bits of the Tree of Life web project (which is where you'll find the photos of P. audax I linked to above), places Phidippus among the Dendryphantinae, salticids that are phylogenetically distant from the ancestral form. Most of these are New World spiders; Eris and Dendryphantes are the only two genera I've heard of in my insular European world. (Incidentally, you shouldn't assume that Dendryphantes is ancestral to the clade. Maddison's cladogramme shows where the Dendryphantinae fit in among the salticids, but not how the dendryphantines relate to each other. That the genus gave the subfamily its name may simply reflect the fact that European naturalists described the local members before anybody described their New World cousins.) I'd be very interested to learn more about what systematists think of dendryphantine phylogeny, and why lots of species of a couple of genera ended up in the Old World while most of their relatives are in the New.

Maddison, BTW, has an extremely impressive jumping spider website. By its title, it deals only with American salticids from north of Mexico, but don't let that fool you. Be sure to visit the gallery, which includes a virtual tour through a jumping spider. This is an excellent introduction to spider anatomy in general and to salticids in particular. Don't miss the chapter on their eyes, a part of the jumping spider that (rightly) so fascinates everybody who takes a look at these charming little animals.