|Female Black-and-yellow Argiope. Be sure to click on this photo to enlarge it so that you can see the characteristic zig-zag stabilimentum that she weaves into her web.|
An interesting feature of the argiope spiders is that they weave a ribbon of silk called a stabilimentum into their webs; this stabilimentum is often in a zig-zag pattern. Although entomologists cannot agree on the true purpose of the stabilimentum, there are several theories as to why argiope spiders expend energy to create them. One possibility is that it adds to the stability of the web. Another idea is that the stabilimentum is easily seen by birds and mammals that as a result avoid the web and therefore don't destroy it. Others think that the structure helps to camouflage the spider, while some think that the stabilimentum may actually attract potential prey. Regardless of its purpose, each species of argiope spider produces a distinctive stabilimentum that helps biologists distinguish between species by only looking at the webs.
There are five species of Argiope in North America, with a sixth (Bruennich's Argiope, Argiope bruennichi) potentially present in Alaska. Of the five species in the continental United States, three have fairly restricted ranges. The Silver Argiope (Argiope argentata) is primarily known from the southern parts of California, Texas, and Florida, as well as from Arizona. A similar species, Argiope blanda, is known in the United States only from the southern tip of Texas. Florida Argiope (Argiope florida) can be found in the southeastern United States, from North Carolina to Florida and west to Louisiana; it may also be found in Arizona. The other two species are widespread. The one I see most frequently is the Black-and-yellow Argiope (Argiope aurantia).
|Female Black-and-yellow Argiope, dorsal side.|
|Female Black-and-yellow Argiope, ventral side.|
|Female Banded Argiope, dorsal side.|
|Female Banded Argiope, ventral side.|
If you are one of those people who is deathly afraid of spiders, I hope that this at least gives you a better respect for the argiopes. If you are one who likes spiders, be sure to get out in the next couple of weeks before it gets too cold to admire these large black and yellow arachnids.