Hacklemesh Weaver Spiders

Amaurobiidae—Hacklemesh Weavers

(Amaurobius and Callobius species)

Amaurobiids are often found under bark, leaf litter, and stones, as well as in woodpiles and other protected areas. They may be found in damp basements, especially during the fall and winter.

Description

Callobius bennetti male. Tom Murray, BugGuide.net, photo# 348659

The females range from 5 to 14 millimeters and the males from 5 to 12.5 millimeters in length. The carapace is a reddish mahogany brown, darkest at the front in the region of the eyes and the chelicerae. The legs are lighter in color than the carapace. The abdomen is generally gray, although the background color varies from a pinkish flesh color to a dark charcoal gray. A pattern of lighter areas or spots (which sometimes run together) can produce a larger, lighter central area. It is common to have chevron-type lighter areas on the posterior portion of the abdomen.

The web is an irregular "mesh" with an ill-defined tube retreat.

Life History/Behavior

The males overwinter as immature spiders, molt twice the following spring, and become adults in April. They die after mating. The females have been found during all seasons, indicating that they probably live for at least two years. The egg sacs are deposited in the same locations that the spiders are found—often in the webs. The number of eggs found in the sac ranges from 73 to 175.

Medical Importance

These spiders are frequently found in damp basements and other areas of the home in autumn. However, there are few indications that these spiders will readily bite or that the bites are medically important. The one verified record of a bite by an immature Callobius species resulted in pain, itching, swelling, redness, and nausea.

Reference

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Levi, H. W. 1959. "The Spider Genus Latrodectus (Araneae, Theridiidae)." Trans. Amer. Microscopical Soc. 78(1): 7–43.

Long, D., R. Snetsinger, and K. F. Helm. 1995. "Localized Pruritic Rash Due to Recurrent Spider Bites." J. Geriatr. Dermatol. 3(6): 186–190.

McKeown, N., R. S. Vetter, and R. G. Hendrickson. 2014. "Verified spider bites in Oregon (USA) with the intent to assess hobo spider venom toxicity." Toxicon 84: 51–55.