Giant lichen orbweaver (Araneus bicentenarius) adult female

Report and Photographs Courtesy of Dawn S., Helotes, TX, 19 July 2007

Editor's Notes by Jerry Cates

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Dawn Wrote:

Jerry--This lady is out on my front gate. I live north of Helotes, Texas, off of Hwy 211 (outside of San Antonio) We took these pictures about 7pm this evening. Have never seen one like it before and don’t seem to be able to find anything to match it on the web. I'm hoping that you can help. Thank you, Dawn S.

Editor's Notes: Besides the green lynx (Peucetia viridans) and a few small crab spiders, not many arachnids are bright green in color.  This species, the giant lichen orbweaver (Araneus bicentenarius) is an exception. Its common name derives from its appearing, to one who happens upon it in the wild, as a displaced chunk of bright green lichen caught, as it were, in a web.  On closer examination, the "chunk of lichen" scampers up its web to a place of safety, or drops to the ground to hide in the grass, revealing that it is, in fact, a living animal, and more specifically a spider of some repute.

The genus Araneus is comprised of "angulate and round-shouldered orbweavers".  This refers to the conspicuous protuberances on the anterior dorsal abdomen. Another important anatomical feature of this genus is the architecture of the thoracic groove. In the genus Neoscona, and in many other spider genera as well, a longitudinal groove separates the thorax, behind the head, into right and left halves. In the genus Araneus, this longitudinal groove is absent, and is replaced by a transverse groove at the base of a somewhat muted cephalic groove.  In the photo below, the transverse groove can be seen as a darkened mark; in the photo above, note that the thorax is smooth where the longitudinal groove would normally be found (were this a member of the genus Neoscona).

Spiders in this genus construct orb webs with open hubs, in contrast to the Argiopes, whose orb webs have closed hubs that are often decorated with conspicuous stabilimenta. 

The giant lichen orbweaver (Araneus bicentenarius) is found in the United States and in Canada, and was first described by the Reverend Henry C. McCook (1837-1911) in 1888. McCook, a renaissance man of immense intellect, served in the Union Army as a first lieutenant and chaplain with the Illinois Volunteers during the Civil War (along with many other members of his family, who were collectively known as "The Fighting McCooks"). Later, in 1870, McCook became the minister at Tabernacle Presbyterian Church, Philadelphia, Pennsylvania. 

Though an active theologian the remainder of his life, in 1873 McCook began a thorough study of spiders and ants, and eventually became president of the American Entomological Society (1898-1900). His three-volume work, "American Spiders and Their Spinning Work---A Natural History of the Orb-Weaving Spiders of the United States, with Special Regard to Their Industry and Habits", remains a treasured treatise on spider behavior. It is said he originally intended to write a natural history of all North American spiders, in one volume. As his studies continued he soon recognized the futility of that endeavor, and finally settled on a less ambitious study of orbweavers alone.

But I digress...

As I am often wont to do--being never satisfied with the delectable offerings provided by those who so kindly send their beauteous photographs to me--I asked Dawn if she might attempt to photograph the ventral anatomy of this creature.  Of all the photographs yet published of this species, none shows the ventral abdomen well.  Inasmuch as that portion of orbweaver anatomy often (see, for example, the markings adorning the various Neosconae) shows markings, not to mention structures, of distinction, I was anxious to have a look.  Dawn sweetly answered my request in the affirmative, and now her illuminating photographs have been published on a separate page.  

Dawn is a superb photographer, and is (actually, she, her husband, and her daughter) equipped with, it turns out, several excellent cameras. Of course, her subject, the giant lichen orbweaver, was also quite photogenic.  We should expect to see this somewhat rare species in greater numbers than usual this year, owing to all the rainfall we've had.  Some specimens have been reported with abdomens measuring an inch or more in length, rivaling the size of the yellow garden spider (Argiope aurantia). High rainfall levels have set the stage for large numbers of flying insects, like crickets and grasshoppers, to emerge during the summer and early fall months.  They will then feed these spiders in such bounty that they will likely become quite large. 

Many thanks to Dawn S. for these excellent photos!!!