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Black Widows

Genus: Lactrodectus 

Actual Size: 3-10mm

Characteristics: Black or dark brown. Females have red or orange markings on the underside of the abdomen, sometimes in the shape of an hourglass. Males have white, red, or orange markings on the top of their abdomen. Some species of widow spiders have no markings and are a paler brown.

Behavior: 

  • Black widow species have extremely poisonous venom, though it is rarely fatal.
  • It is only the female widow spider that has a potent venom; males have a far less intense poison.
  • Black widows are generally non-aggressive. Most humans are bitten after squeezing or pinching a widow spider.
  • Female widow spiders eat the fertilizing male after breeding.
  • These spiders prefer to nest near the ground, in dark and undisturbed areas.
Category:

Pest Description

Black Widow Spider Behavior

Black widow spiders can be found on every continent with the exception of Antarctica. Within the United States, they are most common in the southern and western areas of the country, though they can be found in all 50 states.

The adult female is commonly jet black, with red or orange markings on the underside of the abdomen. Some markings can be “hourglass” shapes, though there are many variations within the widow spider category. Male widow spiders have markings on the upper-side of the abdomen, and those can vary greatly, some with stripes or dots, and a mix of red, or red and white, coloring. Adult female widow spiders are nearly 1/2 inch long, and males are about half this size. There are some species of widow spiders that have no markings, and are a pale brown.

Like most weaver spiders, the black widow spider has poor eyesight. They prefer to build a web close to the ground, in undisturbed and dark areas. The widow spiders build irregular webs with sticky areas, resting in a small central area while waiting for prey. Outdoors, they spin webs underneath wood piles, boards, and outdoor furniture. They also spin webs inside irrigation boxes, behind shrubs, and within wood siding. The black widow does not prefer to enter buildings, but they may do when the need arises.

Black widow spiders mate in the spring or summer, and female widows will eat the male spider after breeding. Females lay eggs in a white, tan, or gray sac with a paper-like texture, suspending the sac within the web itself. A single sac can contain up to 400 eggs, and the female widow spider guards it carefully.

Four weeks later, the eggs will hatch into spiderlings. Widow spiderlings eat one another in the earliest stages of life, so many will not survive. Adult female widows will typically live for 18 months, while male widows only survive for two to five months.

Problems Caused by Black Widow Spiders

The obvious problem with black widow spiders are their bites. Although they are non-aggressive and will only attack when continually provoked, their venom is toxic to the nervous system, and can cause extreme physical reactions. The most common incidences of bites happen when children or pets accidentally invade a web, surprising the female.

Black widow spider bites produce a sharp, pinprick-like pain, leaving two faintly red puncture wounds. Within 20 minutes to an hour, symptoms will begin. These symptoms can include stiffness and intense pain in the bite area, nausea, severe abdominal cramping, tachycardia, muscle spasms, chills, and fever. Immediate medical attention is necessary if a bite is suspected or confirmed. Although a black widow spider’s bite is rarely fatal, the venom can cause symptoms for days and sometimes weeks.

Preventing Black Widow Spider Infestations

There are some basic steps that can be taken to prevent black widow spiders. Because black widows feed on other insects, regular pest control should be employed to limit a food source for black widows. Always use gloves when gardening or performing lawn maintenance, especially within garages or outbuildings. Reduce clutter in these outbuildings, especially cardboard boxes and bins. Keep any stored items off the ground and away from the walls. Outdoor equipment and furniture should be inspected regularly for black widow spiders, webs, and egg sacs. Trim any plants or vegetation from around the home, seal any foundation or wall cracks,  and remove any yard debris. If black widow spiders are discovered, a professional pest control professional should be called before an infestation can result.

Controlling and Eliminating Black Widow Spiders

Because black widow spiders are poisonous, a pest control expert should always be consulted upon discovery. If an wide-spread infestation is suspected, a professional will be able to inspect, treat, and prevent future black widow spider problems. At Pest Control Inc., we use a variety of techniques to prevent and eliminate black widow spider infestations.