Saturday, September 29, 2012

shamrock orb weaver ~ 09/29/12 ~ Rocky Creek

shamrock orb weaver

Spiders and snakes, oh my!  It's that time of year - the month of Halloween.  Spiders have been around all summer (and in most cases, all year round), but it seems the orb weavers are often noticed in the autumn when the females are huge and about ready to lay eggs.  Close to this one, we also found a very large dark grey orb weaver that I think might have been Araneus andrewsi, but I didn't get a clear picture of it.

It's unfortunate that spiders are so misunderstood and misidentified.  To accurately identify most spiders, one would need to microscopically look at the genitalia. Depending on the age, the sex, and possible other factors, different individuals of a single spider sp. can look vastly different from each other.  A look-alike spider to the one I have above is the cross orb weaver (Araneus diadematus). The difference to me is the shamrock has a more spotty look, whereas the cross orb weaver has a definite elongated flower-petal cross on the abdomen, with a prominent "petal" closest to the cephalothorax. Clare at Curbstone Valley Farm has a great new post on cross orb weavers, which are quite common garden spiders.

I'm still looking for a decent spider ID site.  Steve Lew, associated with U.C. Berkeley, had a fabulous spider site, but his research page has been abandoned.  Maybe he finished his PhD and moved on?  Speaking of U.C. Berkeley, they do have two quick reference guides for common CA big spiders and small spiders.  BugGuide (linked in the scientific names above) is okay, but you have to already have a good idea of what you have or wade through thousands of pictures to find a match.  I still use my old handy-dandy A Golden Guide Spiders and Their Kin, originally published by Western Publishing Company, Inc., to get in the ballpark of which spider I have.  I guess St. Martin's Press is now printing the books, but I haven't checked out the new books, yet.  I'm keeping my eye on as a developing and potentially great spider site. I just hope they don't go the way of and place adverts in prime content areas.  U.C. Irvine has a nice page of arachnids of Orange County, but they don't include any of the spiders I've mentioned here.  Perhaps, they're too far south?  I'm going to continue looking for additional spider links, but the first couple dozen sites I found had so many errors that I didn't want to include them.


GretchenJoanna said...

Your photo is striking, the way you caught the spider in mid-air and so crystal clear against the sky.

Katie (Nature ID) said...

Thanks, Gretchen! My little point-and-shoot camera usually has such a hard time focusing on spiders seemingly hanging in mid-air. This one is perfectly decked out in Halloween colors.

Jennifer said...

Nice sighting! Pretty spider.