Spiders and Their Control

There are more than 900 species of spiders native to Texas, but only a handful that are dangerous to humans. Most spiders are at worst harmless, and usually beneficial because they trap and eat insects.

Spiders themselves are not insects. They are members of class Arachnida (which also includes scorpions, ticks, and mites) and order Araneae. Unlike insects, spiders have eight legs (insects have only six) and two body segments (insects have three). In spiders, the head and thorax are fused into one segment called the cephalothorax. Most spiders have eight eyes, and all spiders possess poison glands which are used to paralyze their prey.

Poisonous Spiders Common to Texas

Although all spiders have poison glands, only a few are harmful to humans. Of these, only two species are commonly found in Texas: the Black Widow and the Brown Recluse.

Black Widow Spiders

Female black widow spiders are usually shiny black in color, with a distinctive hourglass-shaped marking on the underside of the abdomen. The hourglass is usually red, but can also be various shades of yellowish-orange. They're about half an inch in size and are commonly found in dark, secluded, protected places like woodpiles, hollow stumps, outhouses, animal burrows, electrical and mechanical boxes, old tires, rubble, and crawl spaces.

Contrary to popular belief, black widow spiders are not particularly aggressive unless they are protecting their egg sac. But they can and will bite if they are threatened, so their control should be left to professionals. Control may consist of physical removal, habitat modification, or the application of insecticides to infested areas.

Black widow spider bites usually are not fatal to healthy adults, but medical care should be obtained immediately as a precaution if a person is bitten by a black widow. This is especially important if the person is a child or an elderly person, has known allergies to spider bites or other types of stings (bees, wasps, etc), or has a heart, respiratory, or any other chronic health condition.

In healthy, non-allergic adults, black widow bites usually cause an initial pain that feels like a pin prick. This pain quickly gets worse, and often spreads to the abdomen and then back to the bite location. Severe abdominal cramps, nausea, sweating, tremors, and difficulty breathing may also occur and can last for several days.

Brown Recluse Spiders

Brown recluse spiders (often called "fiddlebacks") range in size from one-quarter to three-quarters of an inch in length and are predominantly yellowish-brown in color. They have a dark brown, violin-shaped marking on the top of the cephalothorax (where the legs are attached). They also have six eyes (two in front on two on each side).

Brown recluse spiders build their webs in secluded locations such as dark corners, behind stored objects, in hollow tree stumps, and in manholes and utility tunnels. Unlike most spiders, they derive a significant portion of their diet from scavenging.

Brown recluse spider bites can be serious. In most cases, redness and swelling will occur at the bite site within a few hours after being bitten, sometimes followed by nausea, fever, joint pain, dizziness, general weakness, and restlessness. The skin around the bite site then developed a white, raised blister and begins to die. This is called necrosis, and it may spread to surrounding tissue and cause gangrenous ulcers.

Brown recluse bites can be fatal in children, the elderly, and people who already are ill. Even in healthy adults, they can take months to heal and may leave scars. Therefore, anyone bitten by a brown recluse spider should seek medical care immediately.

Obviously, control of brown recluse spiders should be left to professional exterminators. Control methods may include physical removal by trapping, habitat modification, and the use of insecticides in affected areas.