Friday, November 14, 2008

Spiders in Texas

As winter weather approaches, spiders are sure to come inside the home. Spiders are closely related to ticks and scorpions, all belonging to the Class Arachnida. Most spiders are small and considered harmless to humans. In fact, they are beneficial to our environment by controlling insect populations. However there are two groups in Texas that are considered harmful to humans, the black widows and the recluse spiders.
As a warning, all spiders will bite if provoked. Also many people are very afraid of spiders, a condition called arachnophobia.

Dangerous Spiders:

Recluse Spiders

There are five species found in Texas, but only two species are considered dangerous. Their color varies from orange-yellow to dark brown and they are the about the size of a quarter. Their most distinguishing characteristic is the eye pattern and the violin marking on the top side of its first body region, the cephalothroax. These spiders have six eyes arranged in three pairs, forming a semi-circle. The eyes also form the base of the violin shape that extends to its abdomen.
Recluse spiders are shy and will hide during the day. They are most active at night, so people are usually bitten at night. Recluse spiders are usually found in garages, wood piles, cluttered attics, closets bathrooms, bedrooms, and under furniture.
The recluse spiders’ bite may cause effects immediately or be delayed, depending upon the amount of venom injected. The bite usually causes a stinging sensation followed by intense pain. Within 24 to 36 hours, fever, chills, nausea, weakness, and joint pain may result from the bite. The bite will also produce a blister surrounded by a swollen area. The venom kills the skin tissue, which gradually sloughs away until medical attention is sought.

Widow Spiders

There are four species of widow spiders that exist in Texas. Their color varies from brown to black, but all have a marking consisting of two united triangles that can be red, yellow or orange in color. This hourglass marking is found on the underside of their abdomen. The females are 1 ½ inches in length and have eight eyes in two rows, which is a common eye pattern for spiders. Females in a few species of widow spiders will eat the males after mating, which gives this group its name.
They usually live in protected areas around houses and may live in garages, basements, furniture, shrubbery, rain spouts, gas and electric meters and in other undisturbed areas. They spin coarse irregular webs that expand as the spider matures.
The widow’s bite may initially feel like a pin prick that leaves a swollen area with two red spots in the middle. The pain usually becomes worse, causing high temperatures, tremors, nausea, vomiting, leg cramps, perspiration, loss of muscle tone and rise in blood pressure and even death. However, death results in less than 5% of the people bitten by a widow spider.
Photo of black widow spiders. Photo from Texas A&M University, Department of Entomology.

Other Common Spiders:


These are large, hairy spiders that vary in color from brown to black. Adults are usually more than 3 inches in length. They tend to spend the day in hidden areas or under rocks and hunt at night feeding on crickets, caterpillars, and other insects. Since they are spiders, they can bite; however, their toxin is not considered harmful to most people. Also they possess hairs that can penetrate the skin, which cause irritation.

Wolf Spiders

These spiders vary in color from brown to black and some have longitudinal stripes running along their bodies. Wolf spiders are large and can be seen at night under lights. They frequently enter homes and in landscapes, but their toxin is not considered harmful to humans.

Southern House Spider

These spiders sometimes are confused with recluse spiders, but they are larger than recluse spiders. Also they are dark brown in color, have eight eyes all in one cluster, and lack the violin marking. Southern house spiders have distinctive webs that radiate from a central mass that is located in a hole or crevice. These spiders are most commonly found in old barns and in undisturbed areas within human structures. However, their toxin is considered harmless.

Spider Bites

To relieve swelling, apply an ice pack or alcohol directly to the bite. If a severe allergic reaction occurs, a doctor should be consulted immediately. It is always helpful to take the spider along to the doctor/hospital for positive identification.

Some Control Options for Spiders

Non-Chemical Control:

Seal cracks using caulk, weather stripping, and screens to prevent spider entry into the home. Make sure that all stored boxes are taped and sealed to prevent spiders from entering. Also, vacuum webs throughout homes. Since some spiders lay their eggs within the webs, vacuuming will prevent these eggs from hatching.

Chemical Controls:
Only use products labeled for spider control or in areas where spiders are found. These products can contain such chemicals as permethrin, deltamethrin, or bifenthrin. Outside spray or dust under roof eaves, porches, and window ledges. Inside spray around windows, door frames, baseboards and in attics and other places of storage. Some spiders are hard to control, so it is best to contact a pest control professional.

1 comment:

Sudeepta said...

Its a very nice post you are very well known about the spiders do you like them.
Hog Hunting