Rotating News Article

for: Week of January 28, 2002

by: Mike Donahoe

County Extension Director and Pest/Row Crops Agent

Santa Rosa County

Venomous Spiders in Northwest Florida

Arachnophobia (fear of spiders) is widespread. Hardly a week goes by that someone does not walk into the Extension office with a spider tightly sealed in a jar or some other container. “Can you tell me what kind of spider this is?”, they ask. What most people are really concerned about is whether the one they found is poisonous.

Actually, almost all spiders have venom, but only a few are considered to be dangerous. Few spiders will bite, and the bite of most of those large enough to penetrate the skin causes no harm at all. Even the tarantula will not bite unless provoked and is not poisonous. However, the bites of tarantulas can be painful because of their large fangs.

There are about 1,000 species of spiders in the U.S. but only the widow spiders, recluse spiders, and hobo spider are considered dangerous. Of these, only the southern black widow and brown recluse are seen in Northwest Florida.

The southern black widow is our most common venomous spider. It is easy to identify – glossy black with a red hourglass mark on the underside of the abdomen. It is usually found outdoors in protected places such as in storage sheds, crawl spaces under buildings, firewood piles, rainspouts, flower pots, etc. The black widow’s bite is not always felt, but may be like a pin prick. A slight swelling occurs later with two tiny red spots and redness surrounding the bite. Muscular cramps begin within 15 minutes to 3 hours in the shoulder, thigh and back areas. In severe cases, pain spreads to the abdomen, the blood pressure rises, and there is nausea, profuse sweating, and difficulty in breathing for up to 48 hours. Death may result, depending on the victim’s physical condition, age, and location of the bite. However, death seldom occurs if a physician is consulted and treatment is prompt.

The brown recluse is not an established species in Florida, but physicians have diagnosed its bites. Personally, I have never seen one in Northwest Florida since moving here nearly 25 years ago. They are very common a few hundred miles northwest of here in the Mississippi Delta, Arkansas, and Missouri.

The brown recluse is a tan to dark brown spider and has a dark brown violin pattern on the carapace (top part of the body directly above the legs). The neck of the violin points toward the rear of the spider. Another distinguishing characteristic is that the brown recluse has six eyes, while most spiders have eight.

The brown recluse is a shy species that bites humans when trapped in clothing or bed linens. Persons bitten by the spider usually do not feel pain for two to three hours. A blister arises around the bite area. Local pain becomes intense with the wound sloughing tissue often down to the bone. Healing takes place slowly and may take weeks or months. If the bite of a brown recluse is suspected, collect the spider and consult a physician immediately.

Spiders are kept under control around the home by frequent cleaning of areas where they like to live. Regular, thorough vacuuming behind furniture and stored articles, in corners, and in closets will help eliminate spiders and their webs. Repair torn screens and broken windows, and ensure that doors are able to close tightly without gaps. Outside, caulk holes and crevices in foundations or walls and eliminate piles of debris, lumber, and other material near the house.

Consider chemical control only when necessary. Inside the home, space sprays containing pyrethrins or pyrethroids (permethrin, cypermethrin, etc.) are effective. Before applying insecticides, always read and follow the instructions on the product labels.

Actually, spiders in general are considered beneficial and are essential to nature’s balance. They may number two million per acre in undisturbed grassland areas, and destroy more insects than all other animals combined.

If you need help in identifying spiders or other creatures you may be concerned about, contact your local Cooperative Extension office.

Extension Service programs are open to all people without regard to race, color, sex, age, handicap or national origin.

Mike Donahoe is County Extension Director and Pest/Row Crops agent for Santa Rosa County.