Spinybacked Orbweaver, Vol. 4, No. 31

Spinybacked Orbweaver

Gasteracantha cancriformis

Order: Araneae
Family: Araneidae

You might think these would be called “crab spiders,” but that name is already taken by another group of spiders.  However, the second part of their scientific name, “cancriformis,” does acknowledge their crab-like appearance.
 
Spinybacked orbweavers are common throughout the South, especially in late summer and fall.  They build their webs along the edges of wooded areas and in home landscapes, and these are often just the right height that you can’t help but notice them, or walk through them.  Occasionally gardeners, hikers and others who spend a lot of time outdoors in the fall are bitten by one of these, usually because they unknowingly walked into a web and then swatted the spider as it was crawling on their skin.  But it is not a big deal.  Most people find the bite to be a about as painful as a fire ant sting, and there usually are no lasting ill effects.
 
Spinybacked orbweavers are distinctive and easy to identify, but they vary considerably in color.  The females always have six pointed spines on their shell, but the shell color is either white, yellow or orange, and the spines are either black or red.  Males are smaller and do not have spines.  Even though these spiders are fairly conspicuous and remain on their webs during the day, that hard, spiny shell provides excellent protection from birds and other predators.  They are just too hard and spiny to swallow. 
 
There are several other species of orbweaver spiders with spiny shells, but their shape is different and they are easy to distinguish from spinybacked orbweavers.