Bay Journal

Despite their reputations, most spiders are harmless

  • By Kathy Reshetiloff on November 01, 2006
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The American house spider, above, is responsible for many of the cobwebs seen in homes.  (Joseph Berger / www.insectimages.org) The black widow spider, right, while not aggressive, will bite instinctively when touched or pressed.  (Ronald F. Billings / Texas Forest Service / www.insectimages.org) A spider’s silk is secreted as a liquid that hardens on contact with air. Different types and textures of silk may be used to construct snares or webs to capture prey.

I spent five months hiking the Appalachian Trail from Georgia to Vermont. During that time I, of course, camped out in the woods and fields along the way. An injury forced me to leave the trail in August.

My house had been pretty much closed up during that time so when I returned home I wasn’t prepared for what awaited for me.

Spiders! Everywhere. On the deck. In the house. In the shed. In the compost bin. Even in my car. I saw more spiders that first day at home than I had seen on my entire hike along the trail.

As silly as it is, I have to admit that I am a bit of an arachnophobe. Over the years, I’ve become accustomed to the small ones. I usually leave them alone or just pluck them away if I don’t want them in a particular place (like my steering wheel). It’s just the big ones, like the wolf spider I found in my compost bin, that make my skin crawl.

But despite my irrational fears, I left most of the spiders alone. Most spiders are shy and harmless to people. Like many other types of wildlife, they will not bite you unless they are trapped or held.

And of course, spiders feed on many kinds of insects. They are important in controlling many pest insects in gardens or, in my case, house.

Plus, they’re pretty interesting animals. Spiders are not insects but belong to a closely related group called arachnids. Spiders have eight legs and lack wings and antennae. They have two body parts: a cephalothorax which is a head fused with a thorax and an abdomen. Most spiders have eight eyes. Young spiders, called spiderlings, resemble adults except for their smaller size and coloration. Males are usually smaller than females.

Some make webs; others, such as wolf spiders, actively pursue their prey.

There are many families of spiders, all of which are predators. They feed on a wide range of prey including insects and other spiders

All have a pair of clawlike fangs through which venom can be ejected to immobilize their prey. Because spiders can only ingest liquids, digestive fluids are either injected or regurgitated into the prey.

The tip of of a spider’s abdomen has silk-spinning glands. The silk is secreted as a liquid that hardens on contact with air. Different types and textures of silk may be used to construct snares or webs, egg sacs, drag lines and ballooning threads. Some spiders use web snares to trap prey.

Spiders lay eggs in a silken egg sac, often ball-shaped and hidden in the web or carried by the female. One female may produce as many as 3,000 eggs in a series of several sacs. Eggs may hatch a few weeks later or the following spring.

Spiders mature in one year. For a spider to grow, it must molt (shed its skin), usually four to 12 times. Most spiders live either one to two seasons.

Spiders may overwinter as eggs, spiderlings in the egg sac, immature spiders living outside the egg sac or as adults

Here are a few of the most common spiders one might encounter in the Chesapeake watershed:

  • Cobweb spiders are common household spiders that enter homes and build irregular webs in areas where insects fly or rest, usually in the corners of rooms or windows. When they are active, the web remains relatively inconspicuous, but when these spiders leave a web or die, the web becomes covered with dust and is easily seen. Cleaning or dusting in these areas is usually sufficient to control these spiders. (Well now I know why I have so many webs in my house!)
  • Yellow house spiders are small, about .25 inches long, and move rapidly. They may be found in all rooms of a house. The spiders enter homes in early fall and are active for several months weaving small white webs in confined spaces where they spend the winter. In the spring, they usually emerge from their webs and make their way outside.
  • Wolf spiders are active hunters and do not construct webs. Some can be fairly large and have a frightening appearance. They will not attack people unless they are handled or confined. The bite is not dangerous but can be very sharp. Wolf spiders come indoors most frequently in the fall and are usually found in basements. Exclusion is the best way to keep them outdoors.
  • The black and yellow garden spider is one of the area’s most common garden spiders. It makes a circular, flat, wheellike web in shrubs and other tall outdoor plants. These elaborate and beautiful webs often become more obvious in the late summer and early autumn months. They have poor vision and locate the prey by feeling the vibration and tension of the threads in their web as insects are trapped. Despite their size, these spiders are not dangerous, but can bite if handled.
  • Black widow spiders, while not often found indoors, are common in our area. The female is about a half-inch long, jet black with a bright red hourglass shape on the belly. This red mark is easily seen because she hangs upside down in the web. This poisonous spider is more dangerous to children than adults. The black widow is not aggressive. It will, however, bite instinctively when touched or pressed. Anyone who is bitten should go to a doctor immediately for treatment. It is most often found in basement window wells, beneath benches or porches, in garages and sheds, and woodpiles. To control this spider, wear gloves and carefully remove all materials where it might hide. This spider can be cleaned out of an area simply by knocking the webs, spiders and round, tan egg sacs down with a stick and crushing them under foot. Household insect sprays will kill the spiders when hit directly.

Not everyone can live with even the most harmless arachnids in their home. But killing them should be avoided, if possible.

Spiders enter homes through screens, around windows, doors and cracks. Maintaining tight-fitting screens, using weather stripping and sealing cracks can help to prevent a spider’s entry into a home.

To discourage spiders near a home, remove any items piled or stacked near the house such as trash, lumber, bricks, leaves, flower pots and any other objects that provide homes for spiders.

Regular dusting and vacuuming also helps to controls those already in a home. (Yeah, I know.)

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About Kathy Reshetiloff

Kathryn Reshetiloff is with the U.S. Fish and Wildlife Service’s Chesapeake Bay Field Office in Annapolis.

Read more articles by Kathy Reshetiloff

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