Friday arachnid blogging; or, nomen non est omen

This intermittent series of Friday arachnids has not gone over to an all-crab-spider format, I promise you. It's sheer coincidence that this is the third crab spider in a row. Ah well, she is at least a Philodromid rather than a Thomisid--a spider from the genus Tibellus. At first glance, though, you might not think her a crab spider at all:

She hasn't the typical crab-spider habitus at all (though the shape of her prosoma is very crab-spiderish). In fact what she really resembles, at first glance, is a kind of spider known as Tetragnatha. Now, there's a bit of controversy over where to place the Tetragnathids, systematically speaking; but all the possible places for them can be described as 'not close to the crab spiders'. Yet Tibellus looks like a Tetragnathid, and even acts like one: if you see her in the wild, it will likely be in her characteristic pose, stretched out along a blade of grass.

(A closer glance, of course, and the resemblance begins to dissipate. Most obviously, Tibellus has the tiny 'jaws' (chelicerae) typical of crab spiders. Tetragnatha, by contrast, has enormous hinged jaws that give the family its name ('four jaws'). And Tetragnathids, unlike crab spiders, build webs. (One genus within the family, however--Pachygnatha; stockier beasts than Tetragnatha--gives up web-building when it becomes an adult, going instead on the hunt, like Tibellus).

I found this Tibellus in the wild, but not in her usual stomping-grounds. She was stowed away on a ferry from Formentera to Eivissa. If you look very carefully in the photo, you might see a pair of black dots at the back end of her abdomen. This marks her as Tibellus oblongus. Had the black dots extended in two parallel rows all along her abdomen, she'd have been Tibellus maritimus--and wouldn't that have been so much more appropriate?