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ENGLAND: Spiders are a welcome addition to fall gardens

POSTED: October 16, 2007 5:05 a.m.
Question: It seems to me that I have an unusually large number of spiders in my garden. Should I be concerned?
 
Answer: Having numerous spiders in your garden should be seen as a good thing, and not something to be concerned about. The main downside is the somewhat unpleasant experience of walking into the webs and getting the silk smeared all over your face.
 
This time of year, perhaps the most prominent spider we see in our gardens is the yellow argiope (Argiope aurantia), also known as the yellow garden spider, yellow orb weaver or zipper spider.
 
These large garden spiders are females; the males are much smaller and not nearly as easy to spot. Since the males produce no eggs, perhaps that is why they don’t need to attain a larger size.
 
The female argiope (rhymes with calliope) lays several hundred to more than a thousand eggs in a sack that she spins from silk. She may produce more than one egg sac, which resembles a miniature brown pottery urn.
 
The eggs hatch in autumn, but the tiny spiders do not emerge from the sac until spring. Multiple layers of silk help protect the young spiders from cold, accidents and predators.
 
On average, only two of the many hundreds of young spiders produced by each female live to produce young themselves. Dismal odds for the young spiders, but that’s what it takes for a balanced ecosystem.
 
Although most spiders are venomous, very few of them have mouthparts that are capable of penetrating human skin. The only dangerous spider we are likely to encounter in the garden is the black widow, and although quite common, it is usually hidden under a rock or other out-of-the-way place.
 
One unique feature of the yellow garden spider’s web is the zigzag pattern running vertically through the center of the orb. This structure, called the stabilmentum, is made of heavy silk and may help stabilize the web, as the name implies.
 
Spiders are capable of producing many different types of silk, which vary in thickness as well as stickiness. The silk is produced from a group of spinnerets located on the abdomen.
 
Several different glands supply the spinnerets with silk that varies in amino acid content. The glands give the spider the flexibility to produce different formulas while the spinnerets provide a product of the proper thickness for whatever application is needed.
           
Q: What is the large brown spider that spins its web on my back porch at night?
 
A: This is probably the barn spider (Araneus cavaticus), another large spider that is especially noticed in early autumn. This spider has striped legs, dull yellow streaks on its body and usually a black patch on its bottom with two white marks within the black.
 
Barn spiders are nocturnal, building their webs at night and hiding out during the day. They feed on insects that are active at night, many of which are attracted to the lights from our windows.
 
Barn spiders are also orb weavers, meaning they build circular webs. Most of the orb weavers build elaborate structures with many radiating spokes and concentric circles, but they use fine silk that is nearly invisible.
 
Charlotte, of the children’s book Charlotte’s Web, is a barn spider. Her full name is Charlotte A. Cavatica, taken from the scientific name.
 
The barn spider is often found in rafters and open structures in suburban and rural areas, hence its common name.


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