Wednesday, August 4, 2010

colonial orb weaver ~ 08/04/10 ~ Fort Ord

probable colonial orb weaver on coast live oak
probable Metepeira spinipes (formerly M. grinnelli) on Quercus agrifolia var. agrifolia

posted 08/14/11 - Last Monday Andy and I were driving home from the grocery store along Sunset Dr. through Asilomar. I noticed an older gentleman on the side of the road with a notebook and apparently counting something in the bushes. It's not often that I see a naturalist-type looking at anything but birds and the ocean around these parts. I made a U-turn and rolled down the window to ask him what he was doing. Come to find out he's from the University of Cincinnati and studies colonial orb weavers. A line of cars was starting to back-up behind me, so I had him quickly write down the name of the spider and off we went. I would have liked to have stayed longer to chat with him, but we had ice cream in the trunk. Hey, I'll admit, lately ice cream has a rather high priority in my life... well, at least higher than some stranger and mysterious spiders.

As I was driving away, it occurred to me that I've seen massive groups of spiders that could be considered colonial. They seemed to be particularly abundant last year at Fort Ord, San Carlos Beach, and Elkhorn Slough. If you saw them, you'd remember them, too. And, maybe the spiders I found were the same ones this fellow studies?

I was not successful tracking down an ID last year. The abdomen looked like an Araneus to me, but the webs didn't seem right. Instead of a clear orb-shaped web, the ones I saw looked like massive tangles stretching several feet between branches, interlocking with other spiders' webs. I kept thinking of that old study of spiders administered various drugs, and it looked like a bunch of spiders overdosed on caffeine. If I looked closely, I could sometimes make out an orb. Plus, each spider seemed to have its own hidey-hole consisting of dried leaves silked together. Clicking on the second pic above enlarges it so that the orb is visible in the lower right quadrant and a second smaller spider retreat is at 10 o'clock to the one I'm pointing. As I searched online for a match, I found something similar on randomtruth's Flickr (also of Nature of Man blog fame). However, his ID of a trashline orb weaver didn't jive with the conical rump I found on BugGuide for Cyclosa conica. I marked it for later and promptly forgot about it.

Now armed with a spider name I had never heard about until last week, I tracked down the Cincinnati fellow and e-mailed him the two photos above and a link to randomtruth's picture. With his permission, here's what Dr. George W. Uetz replied, "Your photos are probably Metepeira spinipes (I say probably, as positive spider ID to the species level requires microscopic examination of genitalia). Both photos are clearly members of the genus Metepeira, and given the location and the fact that it it built a colonial web, it was most likely M. spinipes. The Flickr photo ID is an error, as the "trash line" is actually a string of egg sacs. Cyclosa spp. do replace their "trash line" of prey remains with a string of egg sacs as well, but this one is definitely Metepeira spp."

To follow-up, I looked at other Metepeira found in Monterey County. Here are links to range maps Lynette Schimming created and posted to BugGuide from a compilation of Steve Lew's spiders of CA website and Herbert W. Levi's 1977 MCZ Bulletin: M. crassipes, M. grandiosa, M. spinipes, and M. ventura. There might be more species in the area, but that's all I could find. Available images of these spiders look very similar. I believe not all Metepeira make colonial webs, and that's why Dr. Uetz thought it was probably M. spinipes.

I'm amazed that by stopping and asking what someone was doing on the side of the road, I learned about a spider ID that puzzled me from over a year ago. Go figure.

ps - Strictly for PG-13 laughs, check out this vid parody "Spiders on Drugs".


Imperfect and tense said...

Never mind Spiders on Drugs, all this time travelling in posts feels more like Back to the Future. And that was a MacFly?

Katie (Nature ID) said...

Haha! Thanks, Graeme. I almost always backdate posts because I'm determined for my archives to accurately show when I saw the featured item, not necessarily when I blog about it.