Friday, June 23, 2006

Porch Spiders: Ventral

After a streak of good luck identifying various flora and fauna I seem to have finally come to a tough case--I would never have guessed it would be the porch spiders--so common, at least on the porch.


Arachnologist David P. Shorthouse was kind enough to stop by and offer a suggestion, Larinioides cornutus (see comments for The Porch Spiders). I think this spider is too small to be the porch spider, and shows other differences, but the latter may be individual variations. Today I am posting a ventral view of one of these spiders--not the same individual, but the one that offered to pose. The spider appears paler more as a result of differences in the light than differences between the individuals. I gather what I really need is a close look at the reproductive organs--but this is beyond my capabilities. So I'm hoping that the pattern on the ventral surface of the abdomen will be helpful in either eliminating or supporting the suggested identification.

5 comments:

David P. Shorthouse said...

Well, this shot definitely supports the fact that the Genus is Larinioides and there are three possibilities: L. cornutus (Clerck), L. patagiatus (Clerck), and L. sclopetarius (Clerck). The spot to narrow in on to get a good close-up is described here: http://www.accessexcellence.org/LC/SS/wolf_spider/spider_section3.html - scan the page of the "epigynum" - in the case of Larinioides, it'll be a scalloped or finger-like projection.

David P. Shorthouse said...

As an aside, traditionally (and for good reason) when total lengths of spider are recorded, this does not include the legs. Rather, from tip of head region to tip of abdomen is the "total length".

Pamela Martin said...

Thanks for the comments and link, David. Very intersting--my mammalian bias had me assuming that the reproductive organs would be at the end of the abdomen. I'l keep watching these spiders for a chance to get a better look.

I did assume that "length" was length of body, sans legs. These spiders are about 2 cm now--and will be bigger than that by fall.

Crys said...

When I came across your porch spider blog, I jumped! For years I've been trying to find the identity of this creepy fellow as well- a mysterious mystery, because around here, they are EVERYWHERE. (Here, in this case, happens to be Western New York, USA). They are on almost every porch, loving bright lights and neons, and appearing mostly in the evening and nights. I've found them in fields and on the local playground, too... But whatever they are, they are definitely PORCH spiders. Good luck hunting for a name and keep up the great blog!

Anonymous said...

I may have found it! A garden cross spider, (an orb weaver), Araneus diadematus. Apparently there is alot of variation as to what they look like, but this site has some superb pics: http://www.natureportfolio.com/inverts/arachnids_spiders_gcross.php
All spideys on that page are from Europe, but on another (lost) webpage I learned that the we've inherited the species.