Pest Information: Brown Recluse Spiders

Brown Recluse Spiders Loxosceles reclusa belong to the group of spiders known by several names: “brown” spiders, “violin” spiders, “recluse” spiders, and “fiddle” back spiders. There are, depending upon who you ask about a dozen species of “recluse” spiders in the US all belonging to the genus Loxosceles. The name recluse comes from the reclusive nature of this spider. It prefers undisturbed and protected habitats. Outdoors, it can be found living in treeholes, under loose bark, stones, logs, or any sheltered area, but is rarely found living in vegetation. Indoors, the spider is found in closet corners, under objects, and in some cases in clothing and shoes. Brown recluse spiders have been identified in the central-south and midwest states. They may, however, be encountered anywhere because they can be transported inside boxes and furniture from states where the spider is common. Spiders in the genus Loxosceles have venom that is potentially dangerous to humans. “Recluse” spiders have a necrotic poison that causes a sloughing off of tissue around the bite site. The wounds can be difficult to heal with a scar forming in most cases. The venom may also cause a systemic reaction. These spiders only bite people when they are crushed. They are not blood feeders and biting is their only defense. These spiders while generally not lethal are considered a health hazard.

Brown recluse spiders have a body approximately 3/8 inch in length. These spiders are most commonly identified by a dark marking on the dorsal portion of the cephalothorax. This marking resembles a violin, hence the name “violin” spiders. The neck of the violin points toward the abdomen. The marking may be difficult to see in fully mature adult spiders and a flashlight may be needed. The second identifying characteristic is the eyes. Most spiders have eight eyes arranged in some fashion. Loxosceles have six eyes arranged in pairs or dyads with one pair in the front and one pair on each side of the head. Both sexes construct small and irregularly shaped, whitish-grey webs. Females are passive hunters, using their webs to catch prey. Males, however, may leave their webs in search of nearby prey. Infestations are comprised of approximately equal numbers of females and males, and include all stages of developing spiders.

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