Yellowlegged Sac Spider
Colorado Insects of Interest
Yellowlegged Sac Spider
Order: Aranae (Spiders)
Identification and Descriptive Features: Yellow-legged sac spiders of the genus Cheiracanthium are generally yellowish but may be pale grayish-tan. There are no conspicuous markings and only fine hairs cover the body. The 8 eyes are arranged in two straight rows.
Legs of yellow-legged sac spiders are long and delicate, with the front pair somewhat longer than the others. Full grown the body is about 3/8 inch long and with legs extended are about 3/4-inch.
Life History and Habits: Yellow-legged sac spiders can be commonly found among the dense vegetation of shrubs, trees and fields. They hunt at night and do not use webs for prey capture instead locating prey during wandering searches. A wide variety of insects (including eggs) and other spiders may be eaten.
Silk is used extensively for subsequent dispersal, both in ballooning and for bridging between plants. The spiders have a one year life cycle with winter is spent in the adult or subadult stage.
Cheiracanthium mildei is also well adapted to indoor life and is one of the most common spiders found breeding in buildings in Colorado. They do have long fangs and are capable of producing a painful bite; this species is sometimes suspected of being the most common cause of spider bites that occur indoors. If bitten the wound should be disinfected to prevent secondary infection bacteria, which sometimes develops after bites from these species and can produce a larger wound.
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