ECOVIEWS: Spiders are the focus of some intriguing questions
When you walk through the woods in early fall, spiders (and their webs in your face) abound. Following are answers to recent questions I have received about these eight-legged creatures. The answers (with one aside from me) are from L. L. Gaddy, author of “Spiders of the Carolinas,” a field guide applicable to many spiders of the Southeast. (It’s available on Amazon.)
Q: I live in Tennessee and work in an office that has an attic in which there are brown recluse spiders. The pest control man who sprays the office said the only way to kill a spider with the spray is to get a direct hit. He says the residual spray is ineffective in controlling them. Is this true? The bug man sets out sticky traps for the spiders; the traps do catch the spiders, as well as other bugs.
A: It is probably true that direct spray would be more beneficial in eliminating a brown recluse colony, but the first consideration is whether the spiders are really brown recluses or one of their look-alikes. (This is where a spider identification field guide comes in handy.) The exterminator should also check for egg sacs after the initial spray – if the egg sacs persist, you will have the same problem next year.
Q: I live in West Alabama. A large spider built a web on the deck of our house. Someone told me it is called a yellow garden spider and that it is a female. Can you identify the spider from the picture I sent? It has been here for several weeks; we first noticed it in mid-August. When would this kind of spider hatch its young? Do scientists know the purpose of the clearly visible white zigzag running through the center of the web?
A: Yes, your deck spider is the common garden spider (Argiope aurantia), also known as the orange argiope, black-and-yellow garden spider, or writing spider because of the zigzags in its web. One assumption is that the zigzag structure stabilizes the web; another is that it serves as a visual warning that birds avoid, thus preventing them from destroying the web. Either explanation could be correct. This type of garden spider prefers sunny locations. Be on the lookout for its large cocoon-shaped egg sac, which will be laid by the female in the fall. The young will probably not hatch until spring of next year.
Q: Is it true that in most spider species the females are larger than the males? Do all female spiders eat the male after mating?
A: Female spiders are usually larger than males. In the golden silk spider (Nephila clavipes) females are about 10 times larger than the males. Female spiders occasionally eat their mates. This is not always the case, but male spiders have extremely short life spans compared to females and most die after mating.
Q: We live in Tuscaloosa, Ala., in a section of town that was badly damaged by the April 27, 2011, tornado. Our neighborhood used to be quite shady because of all the huge old trees. Now we have no tree canopy at all. Some of our neighbors think we have an infestation of black widow spiders. Does that seem likely?
A: Black widows, especially the northern or woodland black widow (Latrodectus variolus), do prefer sunny light gaps in deciduous woods in the southeastern United States. The tornado created lots of light gaps that previously did not exist. There could well be a spike in the black widow population due to this phenomenon.
Do not be dismayed by the many different kinds of spiders--more than 40,000 have been described worldwide. Instead, embark on a voyage of discovery. Start by learning about some of the major groups you are likely to find in your area, such as orb weavers, or crab, wolf, and jumping spiders. The more you learn about spiders (and their webs), the more you will appreciate them. They are among nature’s most awesome creatures.
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Whit Gibbons is an ecologist and environmental educator with the University of Georgia’s Savannah River Ecology Laboratory.