Dewdrop spiders: kleptoparasites

A few months ago, I joined a Facebook group called Florida Entomology. It's nice to see so many different pictures of insects and spiders and whatnot from around the state. And several of the people who post there are incredible photographers. One recent post caught my eye, because it captured the incredible beauty of a tiny spider that I see relatively frequently in my yard: a kleptoparasitic (food-stealing) spider in the complex Argyrodes/Faiditus/Neospintharus/Rhomphaea. It was particularly interesting to me because just about 10 days earlier, I'd gotten my own first acceptable image of a dewdrop spider from my yard:
Dewdrop spider, sedis incertae. Presumably Argyrodes/Faiditus/Neospintharus/Rhomphaea. Boca Raton, FL, September 18. 2016.

Dewdrop spider, presumably Argyrodes/Faiditus/Neospintharus/Rhomphaea. Boca Raton, FL, September 18, 2016.

Just how small is it? Well, I have a particularly fine macro lens on my camera (this is my DSLR, not my phone), and I was about as close to the spider as I could get and still have it in focus (less than 20 inches). That means the image scale is as large as it can possibly be. If you click the image above, you'll get a file 1496 pixels wide. It makes it look huge. It's not. If that spider were next to a bee's head, it would fit on the eyes. The one from Steve Long's image (the Facebook post I referenced at the beginning of this post) is described as "one-third the size of a grain of rice." The largest ones I've seen are no bigger than their namesake:1 dewdrops. Spiders in this group live a particularly daring lifestyle: they live in the webs of larger spiders, eating the prey that its host doesn't want or isn't fast enough to get or vigilant enough in guarding. Marhsall and Edwards provide a good description of its behavior in Florida's Fabulous Spiders:
This species [Argyrodes nephilae] enjoys the very great advantage of not having to produce or maintain its own web. It actually avoids the main web of the host spider, preferring to hang out on the frame and barrier web strands. Here it waits until wrapped prey is unattended by the host spider. Then it stealthily sneaks up to the prey, dragging a line behind it which is attached to the barrier web line. Once it attaches its own line, it cuts the thread from which the prey hangs. The prey then swings out into the barrier web. If the Argyrodes has done its job well, the host spider will never know it has been robbed. But if the Argyrodes nephilae makes a mistake, the bigger spider will come charging over to reclaim its prize.
Etymology The spider discussed above specializes in living in the webs of one of our largest orbweavers, Nephila clavipes, about which I'm astonished to discover I've not written before on this site, except for in asides on other posts. I'll be sure to rectify that soon. In any case, that large spider, I presume, is where the specific epithet (nephilae) of its tiny kleptoparasite comes from. The genus name, Argyrodes, means "silvery." Speaking of silvery spiders, it's worth pointing out that members of this silvery dewdrop spider group don't live just with the yellow-silk orbweaver. They can also be found in the webs of the more common (in my yard) large orbweaver, the Silver Argiope (Argiope argentata), about which I've written in the past. Here is a shot taken last year that shows both species, so you can get an idea of the enormous size disparity between them:
Argyrodes sp. Boca Raton, FL, September 10, 2015.

Argyrodes sp. Boca Raton, FL, September 10, 2015.

The image above also shows why I haven't written about these little guys before: same lens, same photographer, different luck capturing an image of this little one. Here's a crop from the above photo showing just the argyrid:
Argyrodes sp. Boca Raton, Fl, September 10, 2015.

Argyrodes sp. Boca Raton, Fl, September 10, 2015.

No reason to write a post about that!

Leetle bitty spiders, Part 5

Menemerus bivittatus, also known as the Gray Wall Jumper, is a pantropical species of jumping spider that occurs in four of the southern United States: Florida, Louisiana, Texas, and California (here's an image from Los Angeles that was posted to bugguide a couple of years ago). It's unclear (to me at least), why it has this disjunct distribution, but it was apparently introduced into Florida from the Old World tropics as far back as 1912. It is associated almost exclusively with human habitations. Based on a sample size of one (i.e., me), it seems that when a curious backyard naturalist (i.e., me) approaches it with a camera, it waves its chelicerae (the front "feet") in a warning fashion or threat display, although what kind of threat this 1-cm long arachnid with fangs too weak to penetrate human skin can pose is beyond me. Unfortunately, I wasn't able to capture this behavior with my camera; every shot I have shows her with her chelicerae demurely folded in front of her: One thing I discovered about this spider is that it has an incredibly quick reaction time to the flash of a digital camera. When I was taking these pictures, each time I clicked the shutter button while the spider was in one place, in perfect focus, but in the split second between when the flash fired and the exposure was made, the spider literally jumped to a different location. (I suppose the large eyes characteristic of the Salticidae, or jumping spiders, make it rather sensitive to bright lights!) It was quite a challenge to get any of the shots to come out in focus; I pretty much had to guess how far away and in what direction the spider would jump and prefocus in that general area. A few shots did come out, but I had hoped for far more interesting and diagnostic images, based on how docilely the spider let me approach, despite the foot-waving display. Oh, well. They didn't turn out too badly, I suppose. Like most spiders, despite the rather fearsome appearance, they are beneficial to humans on account of their diet. The UF "Featured Creatures" web page for this species mentions that
All free-living stages feed primarily on small Diptera which alight on buildings, although they are capable of capturing large crane flies twice their length, and larger, heavier muscoid flies.
For reference, here's a crane fly (with 64 North American genera and some 1600 species, family-level (Tipulidae) ID is all you can really get from a photograph):

Crane fly (Tipulidae family), Boca Raton, FL, February 15, 2012

The etymology of M. bivittatus was fun to figure out. The derivation of the genus name, which translates to something like "moon thigh," was a bit of a puzzle until I happened to turn to a book I don't own, but hope to some day:  Spiders of North America: An Identification Manual has as its 73rd and last chapter a magisterial etymological dictionary that is a model of scholarship. According to this work, it was Eugène Simon who, in 1868 at only 20 years old was not yet a master of Greek—but the first edition of his Arachnides de France had already been in print for 4 years!—who named this genus. The first part of the name, Menemerus, is supposed to come from the Greek mene, moon, but (had Simon mastered Greek more fully, as he did later in life) it should have ended in -s (menes). The second part of the name, -merus, is Greek for thigh. Apparently Simon meant the name to refer to the crescent-shaped "thigh" of the male palpal femur. The specific name, bivittatus, is a lot easier: Latin for two-striped (bi + vitta), referring to the stripes on the carapace, easily seen in this view: