Why Spiders Are Beneficial

• Spiders feed solely on insects and other arthropods. This makes them beneficial in helping manage pests.
• Some spiders wander indoors in the early fall when cooler outdoor temperatures force them to find shelter.
• Some spectacular spiders are found in webs outdoors in late summer, particularly the banded argiope and the “cat-face” spiders.
• Common spiders found indoors include funnelweb spiders, cobweb spiders, cellar spiders, and sac spiders.

Spiders are beneficial arthropods, that survive by feeding on insects. Oftentimes they are the most important biological control of insect pests in gardens, fields, forests, and homes. However, their presence is a cause of concern to some people. Many people fear spiders beause of stories or myths. Others object to spiders because of their habit of building webs in and around the home. There are a few spiders whose bite require medical attention, but these are very rare in Colorado.

Spiders differ from insects in that they have eight legs (rather than six) and only two body regions (instead of three). The body regions include the cephalothorax (head and legs) and the abdomen. On the head are usually six to eight eyes, often arranged in pairs. The pattern of eye arrangement is characteristic for the different spider families.

Some spiders capture prey by using webs and venom. Others are active hunters that ambush or capture prey. These spiders physically overpower their prey and then use venom to immobilize them.