Larinioides Orbweaver (Adult Female)

Lake Lavon, TX 07 Jul 2009, Kendra N.

Thanks to Kendra for these excellent shots, taken with a Sony digital camera on the balcony of her apartment near lake Lavon, Texas.

Metazygia Orbweaver Lake Lavon TX Kendra N 070709 Posterior dorsal abdomen

Kendra wrote: "I was wondering if you could help me identify this spider. It lives on my apartment balcony northeast of Dallas, near Lake Lavon. My primary concern is whether or not it is dangerous. I have two children and don't want them bitten. Any help you can give will be very much appreciated."

I wrote back thanking Kendra for the excellent photos, which she had thoughtfully sent at high resolution. Then I added that  this appeared to be an orbweaver in the family Araneidae, and that, because the posterior median eyes (PME) are so close together that they almost touch, it is probably a member of the genus Metazygia, whose four species are distributed throughout the southeastern United States.  I was influenced by the dorsal markings of the abdomen, which seemed much like those sketched in Ubick et al. (2005), on pg. 73. Further, Levi (2002) in his paper "keys to the Genera of Araneid Orbweavers (Araneae, Araneidae) of the Americas", pub. in the Journal of Arachnology 30:527-562, states on pg. 532 that the Metazygia are distinguished by an oval abdomen, widest in the middle without humps (see the photo of Kendra's spider, below, that shows these abdominal features nicely), a glabrous carapace with a black cephalic region, and adjacent PME (that is, they are close together). This specimen meets all these criteria, save the fact that its black cephalic region seems more pubescent than glabrous (the thoracic region is, on the other hand, clearly glabrous). Which is to demonstrate how wrong one can be, even in the face of so much "supportive" evidence...

On 25 November 2009 I received an e-mail from Richard Bradley, associate professor of evolutional, ecological, and organismal (EEO) Biology at The Ohio State University. Dr. Bradley kindly supplied the following remarks:

          "Jerry, the photo taken by Kendra N. at Lake Lavon is very likely an adult female Larinioides (a furrow spider). This is a fairly distinctive orbweaver, common in our area, perhaps rarer in Texas. The species has a relatively shiny appearance, and though the pattern on the folium of the abdomen is variable, it typically has the same general tendency to be darker at the edges of the foliar area, and lighter toward the center (as in Kendra's specimen). The narrow light band around the carapace and the pattern of setae on the cephalic part of the cephalothorax are also fairly useful clues. Of course, one cannot be certain without a specimen on hand, but I'm pretty confident this is, rather than Metazygia, a Larinioides, and quite possibly a Larinioides cornutus." 

The drawings on pg. 74 of Ubick, et al. (2005) confirmed Dr. Bradley correct and I mistaken. It is always an honor to receive corrections from viewers. It is particularly humbling (I mean this in its most positive sense) to hear from so distinguished a scientist. A serious arachnologist with much field experience, Rich Bradley (as he is known by his colleagues) is responsible for maintaining the list of spiders native to Ohio (The Ohio Spider Survey) that was begun by William Burroughs in 1924; he kindly promised to look over all the spider photos on the bugsinthenews website and to supply additional corrections as appropriate. I welcome his inputs.

Furrow spiders are interesting for their unusual ability to overwinter as adults (most orbweavers do not live more than a year). The furrow spiders were, until recently, classified as members of the genus Nuctenea, but are now consigned to the genus Larinioides, which is represented in North America by three species.

...

I asked Kendra if she could try to get some photos of the ventral (underside) surface of this spider, as I don't have any photos of that portion of the anatomy for this genus.  Oddly, no such photos seem to exist in the literature for the Metazygia (ref. my previous mistaken identification), anywhere I've looked. However, those of the female Larinioides are sketched in Ubick et al. (2005) on page 74, as 17.71. That sketch is remarkably similar to the marks depicted in the photos Kendra sent me later.

Take a look at the head, in the above photo, where the lighter portion grades sharply into the darkest portion of the face and chelicerae. See the tiny bright speck just to the left of the mid line of the dorsal head? That's the PME on that side. Spiders generally have six to eight eyes (mostly eight, and always eight in the Araneidae), and one or more of them will catch the ambient light--or that of a flash, if one is used--reflecting it brightly toward the camera. Other eyes will often be conspicuously dark, and it is reasonable to believe that the dark speck to the right of the bright speck (which has not caught the ambient light in like manner) is the adjacent PME. 

The genus Larinioides was named by di Caporiacco, an Italian zoologist, in 1934, and is a combination of the generic name Larinia + the suffix oides = "like Larinia." Perhaps there are gross similarities between the Larinia (named by Simon in 1874) and the Larinioides, but such are not the least bit obvious. The Larinia have slender, elongated abdomens, quite unlike the bulbous abdomens of the Larinioides. It is a curious coincidence, methinks, that Larinia is likely derived from the Greek adjective Larinos, "fat, fatted," which does not fit the spiders in that genus, but which does fit Larinioides rather well. Could di Caporiacco have been referring to the Greek adjective, rather than the genus by that name? Was he making a coy reference to Simon's off-target epithet? Possibly. Ludovicio di Caporiacco (1900-1951) was a scientist with diverse interests. He published several papers on scorpions in 1950, the year before his death.

The photo below has been rotated 180 degrees from its original orientation (i.e., down is up, etc.), to give the viewer a better perspective by which to examine the shape of the carapace.

Hopefully this material heightened your interest in the subject of arachnology. You surely noticed that much is yet unknown about North American spiders. Rather than discouraging you, that fact should make you want more than ever to get involved in helping us fill in the gaps and make strides forward in our understanding and knowledge. The field is still wide open, quite contrary to what you may have previously believed. So, consider doing as Kendra did and get directly involved in pushing our knowledge forward. If you happen across a spider in North America, please photograph your discovery and send me copies of your photos. Whenever possible, every inquiry is answered immediately--I try to answer every email inquiry within minutes of reading it, and every telephone inquiry is answered on the spot, as most (alas, some emails do fall through the cracks from time to time) who call will testify.

 * TERMITE ENCOUNTERS  *  SNAKE ENCOUNTERS SNAKE BITE FIRST AID * SNAKE EXCLUSION * SPIDER ENCOUNTERS FOR 2008 SPIDER ENCOUNTERS FOR 2007 * SPIDER BITE FIRST AID * SPIDER EXTERMINATION * PUSS CATERPILLAR ENCOUNTERS * PUSS CATERPILLAR FIRST AID * PUSS CATERPILLAR EXTERMINATIONAssembled & Edited by Jerry Cates. Questions? Corrections? Comments? BUG ME RIGHT NOW! ---- Ph: 512-331-1111 ---- E-Mail ---- Privacy ----BugsInTheNews * --0a0s--