Black Widow Spiders

Lactrodectus mactans

Black widow spiders are most recognized for the red hourglass shape on the back. Contrary to legend, female black widow spiders rarely devour the male black widow spider after mating.

Color: Black, with characteristic red “hourglass” on back
Legs: 8
Shape: Round
Size: 3/4″ length; 3/8″ in diameter
Antennae: No
Flight: No

Black widow spiders spin their webs near ground level. They often build their webs in protected areas, such as in boxes and in firewood.

Black widow spiders are often found around wood piles and gain entry into a structure when firewood is carried into a building. They are also found under eaves, in boxes, and other areas where they are undisturbed.

The venom of a black widow spider is a neurotoxin and is used as a defense. Black widow spiders do not bite humans instinctively. The black widow spider bite can cause severe pain. Young children and the elderly are especially susceptible to a severe reaction to a black widow spider bite.

Avoid black widow spider bites by wearing heavy gloves when moving items that have been stored for a long period of time. Spiders often hide in shoes, so check shoes and shake them out before wearing. When spider webs are visible, use caution before putting your hands or feet in that area.

Black Widow Biology, Reproduction, and Behavior:
Above is a little bit of information on black widows, but I thought we would go a little deeper for your safety.
The black widow spider is a cobweb builder whose silk is very strong. The female constructs a web of crisscrossed silk threads with no recognizable pattern and with a dense area of silk, usually to one side, that serves as the spider’s daytime retreat. At night, the female hangs belly upward in the center of the web. She does not leave her hidden web voluntarily. The web typically is situated near the ground in a dark, sheltered site. Webs often are one foot in diameter. The web serves to trap the spider’s food, which includes a variety of insects (cockroaches and beetles) and other arthropods. Outdoors, black widow spider webs are usually built in woodpiles, rubble piles, under stones, in hollow stumps, and in rodent burrows. These spiders commonly occur in outbuildings such as privies, sheds, and garages. Indoors, they prefer undisturbed, cluttered areas in basements and crawl spaces.

The northern black widow spider is similar to the black widow except its habitat is marginal land with sparse vegetation. It is found in stumps, hollow logs, and piles of debris, and only rarely indoors.

Bite Symptoms:
The severity of an individual’s reaction to the black widow spider bite depends on the area of the body bitten, amount of venom injected, and their sensitivity to the venom. The venom travels in the bloodstream throughout the body and acts on the nervous system, causing varying degrees of pain. Some people report very intense pain. There typically is no necrosis (sloughing) of tissues and no conspicuous swelling.

The bite of a black widow spider initially may go unnoticed, but some people report a short stabbing pain. At first, there may be slight local swelling and two faint red spots, which are puncture points from the fangs. Pain soon begins and usually progresses from the bite site to finally localize in the abdomen and back. Severe cramping or rigidity may occur in the abdominal muscles. Other symptoms may include nausea, profuse perspiration, tremors, labored breathing, restlessness, increased blood pressure, and fever. Symptoms often diminish after a day or so and cease after several days. Serious long-term complications or death are very rare.

Preventing Spider Bites:
In order to prevent spider bites, be sure to wear gloves and a long-sleeved shirt when handling stored cardboard boxes, firewood, lumber, and rocks. Be sure to inspect these clothing items for spiders before putting them on. Shake out clothing and shoes before getting dressed.

Install tight-fitting screens on doors and windows to prevent entry of black widow spiders. Also install door sweeps. Seal or caulk cracks and crevices where spiders can enter the house. Install yellow or sodium vapor light bulbs outdoors since these attract fewer insects for spiders to feed upon.

In order to reduce black widow spider populations, it is very important to eliminate their potential hiding places indoors and outdoors. Black widow spiders are often found in undisturbed, cluttered areas indoors, so discard old boxes, old clothing, lumber, and other unwanted items in basements, crawl spaces, garages, and outbuildings. In such areas, store any items off the floor and away from walls. Remove piles of lumber and rubble outdoors. Remove ivy and other heavy vegetation from the foundation. Do not store firewood against the house. Note that these measures also reduce harborages for the spiders’ prey.

Vacuum thoroughly indoors to remove black widow spiders and their webs and egg sacs. After vacuuming, immediately place the vacuum cleaner bag in a plastic bag, seal tightly, and discard in a container outdoors—this prevents captured spiders from escaping into the home. Wash off the outside of the house using a high-pressure hose, paying particular attention to window wells and other undisturbed areas where webs are built.


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Black Widow Spiders are very difficult to manage and eradicate on your own. If you need help removing Black Widow Spiders from your home or business, contact Mountain Pest Control, we’re here to help.