Happy Halloween!

Argiope aurantia

Those who think scientific names are too complicated have the following dizzying array of common names to choose from for this species: black and yellow garden spider; black and yellow argiope; yellow garden spider, yellow garden argiope; yellow garden orbweaver; golden garden spider; golden argiope; golden orbweaver; writing spider; scribbler; corn spider. Or instead, just say Argiope aurantia (are-gee-OH-pee our-ON-tea-uh) – it is unambiguous and will make you sound intelligent.

Large females are commonly encountered in late summer and early fall. This fine lady was photographed 7 September 2008 at Victoria Glades Natural Area in Jefferson County, Missouri. Quite coincidentally, North America’s tarantulas (genus Aphonopelma, represented in Missouri by A. hentzi) reach their natural northeastern limit of distribution in this very glade complex, located ~30 miles south of St. Louis.

There are five North American species of Argiope, of which two occur broadly across the eastern U.S. Argiope aurantia can be distinguished from Argiope trifasciata (banded garden spider/argiope/orbweaver) by the zig-zag pattern of the stabilimentum of the former and the transversely striped abdomen and spotted legs of the latter.

Despite its name, the function of the stabilimentum (reinforced area in the middle of the web) remains controversial. The idea that it somehow adds stability to the web is not given much credence today. A visual function seems much more plausible, especially when considering that only diurnal spiders make such structures. Possibilities include camoflauge for predator avoidance, the seemingly opposite idea of increased visibility to prevent accidental destruction of the web by birds or large animals, and even prey attraction through enhanced reflection of ultraviolet light. Stabilimenta in different spider lineages probably evolved independently and may have different or even multiple functions.