1. Education
Send to a Friend via Email
You can opt-out at any time. Please refer to our privacy policy for contact information.

Brown Recluse Spider, Loxosceles reclusa

Habits and Traits of Brown Recluse Spiders

By

Loxosceles spiders display a fiddle-shaped marking on the cephalothorax.

Loxosceles spiders display a fiddle-shaped marking on the cephalothorax.

Photo: CDC
Range of Loxosceles (recluse) spiders in the U.S.

Range of Loxosceles (recluse) spiders in the U.S. Red area highlights the range of the brown recluse spider, Loxosceles reclusa.

Map provided by Rick Vetter, University of California-Riverside. Used with permission.
Brown recluse spiders are fairly small, with bodies reaching just a quarter inch in length.

Brown recluse spiders are fairly small, with bodies reaching just a quarter inch in length.

Photo: Emmanuel.boutet, Wikimedia Commons

The brown recluse spider, Loxosceles reclusa, has a bad and largely undeserved reputation. Across the U.S., people fear the bite of this spider, believing it is an aggressive attacker and certain to cause devastating necrotic wounds. Research on brown recluse spiders has proven these assertions to be false.

Description:

The best known feature of the brown recluse spider is the fiddle-shaped marking on the cephalothorax. The neck of the dark brown fiddle points toward the abdomen. Other than this marking, the brown recluse is a uniformly-colored light brown, with no stripes, spots, or bands of contrasting color. The violin marking is not a reliable identifying characteristic. Young L. recluses may lack the mark, and other Loxosceles species also display the fiddleback detail.

Along with other Loxosceles species, brown recluses have six eyes, arranged in a semi-circle pattern of three pairs. This feature distinguishes Loxosceles spiders from most others, which commonly have eight eyes. The brown recluse lacks any stiff spines on its body, but is covered with fine hairs.

The only definitive way to identify the brown recluse spider, Loxosceles reclusa, is to examine the genitalia. With a body size of just a quarter inch long, this requires a high magnification microscope. Suspected brown recluse spiders should be brought to your county extension agent for expert identification.

Classification:

Kingdom - Animalia
Phylum - Arthropoda
Class - Arachnida
Order - Araneae
Family - Sicariidae
Genus - Loxosceles
Species - reclusa

Diet:

The brown recluse spider feeds at night, leaving the security of its web to search for food. Current research reveals the brown recluse is primarily a scavenger, feeding on dead insects it finds. The spider will also kill live prey when needed.

Life Cycle:

Brown recluse spiders live about two years. The female lays up to 50 eggs at a time, encasing them in a silken sac. Most egg production occurs between May and July, and a single female may lay five times within a year. When the spiderlings hatch, they remain with the mother in her web until they have molted a few times. Over the first year of life, the spiderlings will molt up to seven times before reaching adulthood.

Special Adaptations and Defenses:

Brown recluse spiders use short fangs to inject a cytotoxic venom into prey. When provoked, a brown recluse spider will bite, and this venom may cause necrotic wounds to the person or animal that has been bitten.

Venom is not the brown recluse's primary defense, however. As the name recluse suggests, this spider is quite timid, and spends the daylight hours in retreat, usually in its web. By remaining inactive during the day, the brown recluse limits its exposure to possible threats.

Habitat:

Brown recluses prefer dark, undisturbed areas with low moisture. In homes, the spiders find shelter in basements, storage closets, garages, and sheds. During the day, they may hide in cardboard boxes, folded clothing, or even shoes. Outdoors, brown recluse spiders are found beneath logs, in wood and lumber piles, or under loose rocks.

Range:

The established range of the brown recluse spider is limited to U.S. states in the central Midwest, southward to the Gulf of Mexico. Rare and isolated encounters with brown recluse in areas outside of this range are attributed to interstate commerce. Brown recluse spiders may seek shelter in cardboard boxes, and make their way to places outside their known range in shipments of goods.

Other Common Names:

Brown fiddler, violin spider, fiddleback spider

 

Sources

 

  1. About.com
  2. Education
  3. Insects
  4. Spiders
  5. Brown Recluse Spider, Loxosceles reclusa

©2014 About.com. All rights reserved.