Spiders are not all bad

Tuesday, October 29, 2013

Yes, they have four times as many legs as humans, and for a few weeks each year, they might be used to wring screams of terror from unsuspecting victims, but the truth is spiders are mostly peace loving friends of the environment.

Folklore paints spiders as dangerous, creepy, crawling, venomous creatures, but that is not quite accurate, said Richard Grantham, an entomologist and director of the Plant Disease and Insect Diagnostic Lab (PDIDL) at Oklahoma State University.

“Most spiders do have venom glands, but most don’t bite humans unless provoked, and the venom usually isn’t harmful to people or other mammals,” he said. “Actually, spiders are important predators that keep insect and other arthropod pest populations under control.”

Oklahoma is home to several spiders and related species that are generally harmless to humans such as tarantulas, jumping spiders, wolf spiders and garden spiders. However, two others, the brown recluse and the black widow, are considered dangerous to people.

Also known as the fiddleback or brown spider, the brown recluse has three pairs of eyes arranged in a semicircle on the forepart of its head, a dark-colored, violin-shaped marking right behind the eyes and long legs.

This spider is most active at night. During the day, it rests in quiet, undisturbed areas such as bathrooms, bedrooms, closets, basements, cellars, attics and under furniture.

“A brown recluse usually only bites when pressure is applied to it,” Grantham said. “A lot of times people are bitten while putting on clothes or shoes where the spider is hiding or when they roll over on it while in bed.”

The bite could hurt immediately or, it could take three to four hours for a reaction to occur. Within eight hours, a painful small puss-filled blister surrounded by a larger red and swollen area usually develops. Healing is slow and could take up to eight weeks or longer.

Black widow spiders are always hairless and have eight eyes arranged in two rows.

Females are usually larger than the males, have slim, glossy black legs and a reddish hourglass-shaped spot on the underside of their globular abdomen.

These spiders are frequently found near houses, particularly under eaves, as well as around trashcans, dumps or ash piles, and under boxes, low-growing shrubs, crates, stones and woodpiles. Cold and drought conditions tend to drive them into buildings.

The black widow is generally considered the most venomous spider native to North America. Although a female’s bite commonly causes severe symptoms, especially in young children and older adults, it is rarely lethal.

“It’s especially important to recognize female black widows because their bites are potentially medically serious,” Grantham said. “The females aren’t aggressive unless confined or disturbed, although they are more likely to bite if they are guarding an egg sac.”

If you suspect a brown recluse or black widow spider bit someone, seek prompt medical attention. If possible, capture the spider for identification purposes. For assistance in determining the type of spider, you can contact your local Extension office or send it directly to PDIDL.

Regularly cleaning closets, cellars and similar areas, as well as sealing openings such as windows and doors can help keep your living spaces spider free. Also, where possible, use a water hose to wash down outside areas, especially under roof eaves.