Many Americans warmly welcome four-legged friends into their homes, but few are comfortable when creatures with eight legs wander in from outside.

Even though they make you shriek, some spiders play a positive role around your home by preying on other pests. For some homeowners, their contributions to reducing unwanted insects far outweigh the fear they evoke.

"Many household spiders are not dangerous to humans," said Orkin, Inc. entomologist Ron Harrison, Ph.D. "However, there are a few species with a venomous bite. The key is distinguishing between those that make harmless houseguests and those that present a threat to your family."

Several spiders can protect your home from pesky invaders. Cellar spiders-the web-spinning species most common in homes-have been known to prey on black widow spiders. Some, like the spiny orb weaver and house spiders, can hunt crickets and small flying insects. Wolf spiders can help rid lawns and gardens of common pests. Even the brown recluse-the most dangerous spider to humans-can assist by eating cockroaches, silverfish and other soft-bodied insects.

When protecting your family from venomous spiders, it is important to identify key characteristics of harmful species like the black widow, brown recluse and yellow sac spiders, whose bites can cause severe skin irritations.

? Black Widow: Females are shiny black, with a red hourglass-shaped mark on their abdomen.

? Brown Recluse: This spider is yellowish to brown in color, with a dark brown violin-shaped back marking; legs are long and thin with fine hair.

? Yellow Sac: This spider has yellow coloring; its abdomen is often much brighter than its head or legs.

According to a survey conducted by Orkin, Inc., spiders have a noticeable presence in two out of three American households. So when spiders make frequent appearances in your home, trust an experienced professional to identify the species, consider its web-building or hunting behaviors and determine the best way to control the infestation.

Homeowners can take some steps to prevent spider invasions and reduce potentially harmful encounters, such as removing food sources and discouraging nesting by keeping low-traffic areas, such as cellars or closets, clear. However, a licensed pest control company should be called upon to treat and repel spider infestations.