Illinois Natural History Survey - University of Illinois

Wolf Spiders

 

Susan Post

 

Have you ever been hiking when a large brown spider races across your path, or noticed that at night your flashlight picked up mysterious glowing dots? Perhaps these were chance encounters with Illinois’ version of a wolf—a wolf spider.

Wolf spiders belong to the family Lycosidae and they are among the most common spiders with anywhere from 2,000–3,000 species worldwide.  They are found from the arctic to the tropics. There are 238 species north of Mexico, and Illinois has at least 47 species of wolf spiders. They have  common names such as dotted wolf, rapid wolf, stone, shore, brush-legged, and two-lined.  Their common name comes from their genus name Lycos. In Greek this is the root word for wolf. This may refer to the way the spiders catch their prey—instead of using a web they stalk and chase like a wolf.

Wolf spiders have eight legs and two body parts—the celphalothorax (the combined head and thorax) and an oval abdomen. Their fanglike mouthparts are called chelicerae.  Their legs are long and tapered and adapted for running. To gain traction they have adhesive hairs on the soles of their feet.

Wolf spiders range from a half inch to two inches long and are quite hairy. They are drably marked with off-white, black, yellow, or red on a brownish or blackish background. Their carapace (the top portion of the celphalothorax) often has two or more distinctive dark longitudinal stripes. Wolf spiders are often the same color as their background so they can be hard to see. They are ground-dwelling spiders so look for them under rocks and logs, near streams, in leaf litter, and at the bases of plants. Some will construct burrows in the soil or utilize cracks and crevices in rocks for retreats; others will seek shelter under bark.

These spiders have good vision and a highly developed sense of touch. They have eight eyes,  all dark and arranged in three rows. The four anterior eyes are small, dark, and in a nearly straight line. The posterior row is recurved to form two rows of two eyes each and these are much larger than the anterior eyes. These eyes also have a layer of light reflecting crystals, the tapetum, behind the light sensitive retina, giving the eyes a silvery appearance and causing them to shine brightly in a beam of light.

A distinctive behavior of wolf spiders is the carrying of their egg sacs by females. The female attaches the globular egg sac to her spinnerets (located at the posterior end of her abdomen) and carries it until the eggs hatch. The female will open the seam of the egg sac and wait for the young to clamber upon her abdomen and hang on to her abdominal hairs. If any fall off they climb up their mother’s legs to get back on. They will ride for several days and will be nourished by the yolk within their bodies. After their first molt they descend and are on their own. They will undergo several molts before reaching adulthood. Wolf spiders live for several years.

Wolf spiders are active hunters that patrol the ground for insects and small spiders. Usually patrolling at night, they spot their victim, give chase, capture, and inject it with paralyzing venom. Soon the victim’s dissolved tissues are sucked out. Wolf spiders are also the hunted. They are food for small lizards, insectivorous mice, shrews, and turkeys.

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