Spiders often receive undue criticism as being dangerous to people and pets. Although most spiders produce venom to subdue their prey, unless a person is hypersensitive, few are potent enough to cause results any worse than a bee sting. Most species do not bite humans or have fangs incapable of piercing our skin.
In Kentucky, there are only two spiders, the black widow and the brown recluse, that are known to be poisonous. Fortunately, even though spiders are very abundant, encounters between people and spiders are usually accidental and bites are a response by the spider when its web or nest is disturbed.
Spiders are extremely beneficial because they feed on a large number of insects and other arthropods. They are often the most important biological control of insect pests in gardens, forests, and structures. Some species use webs or snares to trap prey but others are active hunters that stalk and ambush their food. Spiders differ from insects as they have eight legs (rather than six) and two body regions (instead of three). They are close relatives of ticks, mites, and scorpions, all of which are referred to as arachnids. Spiders are identified by size, color, markings on the body and even the number and arrangement of eyes.
Even though spiders should be considered beneficial, they can become a nuisance in homes. Spiders are generally “accidental invaders”, often males that have wandered through doors, windows, or other openings in search of females. Regardless of the spider’s shape or size the immediate question is if the spider is poisonous. This week I thought it may be helpful to review a few of the spiders commonly found indoors and examine some control methods.
Wolf Spiders are one of the larger spiders occasionally seen indoors during cool weather. They can grow to 1/2 inch long and are very hairy, often being confused with tarantulas. Their bodies may be colored with shades of brown, black, gray, white, yellow, orange, or green, but most are dark brown. Wolf spiders do not establish themselves indoors and they are not aggressive, however they do have strong fangs and may bite if handled.
Funnel Web Spiders (also called grass spiders) resemble wolf spiders and the brown recluse. They differ from both because of their distinctive pair of long spinning tubes found at the rear of their abdomen. These are used to build horizontal, sheet-like webs often seen on lawns and shrubs on dewy mornings. Funnel web spiders wait for an insect to cross the web, and then dash out, bite it and carry it back into its funnel shaped nest. This spider can occasionally be found indoors during late summer and early fall. They are 1/2 inch long or more and are marked with shades of gray, brown, white, black, and dull yellow.
Cellar Spiders are about 1/3 inch long and have long thin legs up to two inches long. They are commonly found indoors and build webs in cellars, garages, and other dark areas of homes. Cellar spiders may hang upside down on their webs and shake the web violently when disturbed.
Cobweb Spiders frequently live in buildings making irregular shaped cobwebs in corners of rooms or angles of windows. These spiders are about 1/3 inch long, gray to brown with a rounded, abdomen mottled with several dark stripes on the upper side. Their webs often become dust covered when abandoned.
Accidental invaders rarely require control, however spiders found indoors regularly can be controlled with a few simple techniques. Routine house cleaning is the best way to eliminate spiders and discourage their return. Reducing clutter in closets, garages, and basements will make areas less attractive to spiders.
Installing yellow or sodium vapor light bulbs at outside entrances will attract less night-flying insects and in return you will have fewer spiders. Since spiders feed on insects, eliminating conditions that attract insects (i.e., high moisture, food source) will decrease the likelihood of finding spiders. Keeping woodpiles, trash, rocks, and other debris away from the home outdoors will also decrease spider habitats. Spot treatments with pyrethroid sprays may also help eradicate spider infestations.
Severe infestations of brown recluse or black widow spiders require specialized skills and it would be wise to call a professional pest control operator.
