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Venomous Spiders in Florida 1
D.E. Short and J.L. Castner2Five species of venomous spiders occur in Florida: the southern black widow, northern black widow, red widow, brown widow and brown recluse.
The four species of widow spiders are very similar in body shape. All are about 1/2" long with legs extended. Their life cycle is also similar. The female lays about 250 eggs in a pear-shaped egg sac that is about 1/2" to 5/8" in diameter. The eggs hatch in about 20 days. As the young spiders mature, they construct a loosely woven web and capture progressively larger prey. In Florida, all the widows except the northern black widow breed year-round.
Anyone bitten by a spider should preserve it in rubbing alcohol for positive identification. Most spider bites are not considered dangerous, but if you suspect one of the widow or brown recluse spiders, get medical attention immediately.
- Southern black widow ( Plate 1 ). This is the most widespread widow spider in Florida. It is glossy black and has a complete hourglass marking on the underside of the abdomen ( Plate 2 ). The northern black widow has the same general appearance, but has two red triangles resembling an hourglass and a row of red spots on top of the abdomen. The northern species is found west of Tallahassee, primarily in forests, with its webs three to 20 feet above the ground. The southern black widow is usually found outdoors in protected places, such as under rocks and boards, and in and around old buildings. The bite of the black widow and other widow spiders usually feels like a pin prick. The initial pain disappears rapidly, leaving local swelling and two tiny red marks. Muscular cramps in the shoulder, thigh and back usually begin within 15 minutes to three hours. In severe cases, pain spreads to the abdomen, the blood pressure rises, and there is nausea, sweating and difficulty in breathing. Death may result, depending on the victim's physical condition, age and location of bite. Death seldom occurs if a physician is consulted and treatment is prompt.
- Red widow ( Plate 3 ). This species has a black abdomen and reddish-orange head, thorax and legs. The top of the abdomen usually has a row of red spots with yellow borders. This spider lacks a complete hourglass on the underside of the abdomen and instead usually has one or two small red marks ( Plate 4 ). The red widow constructs its web in palmettos and has been found primarily in sand-pine scrub habitats in central and southeast Florida.
- Brown widow ( Plate 5 ). This spider varies from light gray to light brown to black. The abdomen has variable markings of black, white, red and yellow. The underside of the abdomen has an orange or yellow hourglass ( Plate 6 ). It is found most often south of Daytona Beach along the coast. It usually makes its web on buildings in well-lighted areas.
- Brown recluse ( Plate 7 ). This is not an established species in Florida. It is recognized by the distinctive dark violin-shaped mark located on the head and thorax. The brown recluse is a medium-sized spider about 1/4" to 1/2" long. It is light tan to deep reddish-brown ( Plate 8 ). It is usually found in sheds, garages or areas of homes that are undisturbed and contain a supply of insects to serve as food. Favorite hiding places include arms and legs of garments left hanging for some time or beds that have been unoccupied for long periods of time. Persons bitten by this spider usually do not feel pain for two to three hours. A blister arises at the site of the bite, followed by inflammation. Eventually the tissue dies, leaving a sunken sore. Healing may take as long as six to eight weeks.
Plate 1. Southern black widow.
Plate 2. Southern black widow.
Plate 3. Red widow spider.
Plate 4. Red widow spider.
Plate 5. Brown widow spider.
Plate 6. Brown widow spider.
Plate 7. Brown recluse spider.
Plate 8. Brown recluse spider. Footnotes
1. This document is SP 104, one of a series of the Department of Entomology and Nematology, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. This document is available for sale as a high-quality, color publication. For ordering information or to order using VISA or MasterCard, call 1-800-226-1764. Date first printed: January 1992. Reviewed: May, 2003. Reprinted: February 1997. Please visit the EDIS Website at http://edis.ifas.ufl.edu.2. D.E. Short, Professor; J.L. Castner, Scientific Photographer; Department of Entomology and Nematology, Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, 32611. The term plates, where used in this document, refers to color photographs that can be displayed on screen from the FAIRS CD-ROM. These photographs are not included in the printed document.
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