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Poisonous Spiders

Common names: Brown Recluse, Violin Spider, Fiddleback Spider

Scientific name: Order Araneae, family Loxoscelidae, Loxosceles reclusa

Size: Adult--1" to 1 1/2"

Identification: Adults are light brown in color and have very long legs. Females are larger than the males and have a distinctive dark brown violin shape on the back. They make irregular webs.

Biology and life cycle: Incomplete metamorphosis. Females produce one to five egg sacs with a total of 30 to 300 eggs that hatch in one month. Nymphs pass through eight instars (young forms resemble adults). Total life cycle is about one year. Adults can live from two to five years. They bite in defense when they sense pressure (in clothes or bedding).

Habitat: Under rocks, in loose papers, boxes, clothing, bedding, and shoes. Webs are used as a place to hide rather than to catch prey.

Feeding habits: They hunt at night and feed on various insects.

Economic importance: Brown recluse spiders help control several pest insects, but their bite can cause a serious wound and in rare cases the loss of a limb.

Natural control: Other spiders, wasps and lizards.

Organic control: Physical removal of webs. Vacuum often and spray problem areas with citrus products. Freeze boxes of infested papers for forty-eight hours. Use diatomaceous earth outdoors and boric acid products or plant oil products indoors.

Insight: Bites don't hurt at first but become extremely painful later. There is no antivenin. Shake out clothes that have been on or near the ground overnight or hanging in the closet or garage for a long period. Brown recluse spiders are dangerous but clumsy. They don’t climb glass well but will often get curious about a glass container that is next too a vertical surface, venture down into the glass and get trapped.

Black Widow Spiders

Scientific name: Order Araneae, family Theridiidae, Latrodectus mactans
Size: Adult--9/16" to 1 1/2"

Identification: Adult females have shiny black bodies and a distinctive red hourglass-shaped marking on the underside of the abdomen. The compact webs are off-white and dense. Males are smaller and have markings on the upper side of the abdomen and large eyes.

A large mature female with a prominent red "hourglass" marking.

Biology and life cycle: Young spiderlings are whitish when first hatched but darken quickly. Females lay eggs in spring or summer in grayish silken egg balls. Females spin a small, irregular tangled web with a tunnel that she goes into when disturbed. These webs are usually close to the ground. Females eat the males after mating unless they are fast enough to escape. She lays up to 200 to 900 eggs in a sac within the web. The eggs hatch in about thirty days, have one molt, then escape the web and "balloon" to a suitable spot to settle in. Ballooning is done by spinning a strand of silk and letting the wind blow the spiderling to the new location. Young are cannibalistic--only one to twelve young survive from each egg case.

Black widow spider with its prey.

Habitat: Buildings, rodent holes and burrows, barns, garages, basements, outdoor toilets, hollow stumps, trash, brush, vegetable gardens, and dense vegetation. They particularly like tomatoes and grapes.

Feeding habits: Mostly very small insects.

Economic importance: Bites can be very dangerous, especially to children and debilitated people.

Natural control: Mud daubers and predatory insects.

Organic control: Physical removal of webs. Outdoor toilets are the most common place where people are bitten. Spray plant oil products or dust with natural diatomaceous earth.

Insight: Bites cause little or only momentary pain, but the poison causes severe cramping and aching pain from ten to sixty minutes after the bite. The pain spreads to all the skeletal muscles of the body and causes severe hardening of the abdomen. Most deaths are children and the sick and debilitated. Seek prompt medical attention.