Black Widow Spiders

Picture of Black Widow Spider
Black Widow Spider
© Creative Commons

She’s attractive but instills fear. Rightfully so. She is a dangerous lady spider and has earned the name “Black Widow” because of the mistaken belief that she always kills and devours her mate after he is no longer needed. Although she does sometimes commit this crime, most males scurry off safely after egg fertilization. The Black Widow has a body size of about half to three quarters of an inch plus the length of long legs. The male is a fraction of her size and volume and absent the bright colors.

The black widow spider has distinguishing beauty. Shiny and jet-black with an oversize, globally-shaped abdomen. The western species has a bright red hour-glass design on the underside of the abdomen. The northern species has two bright red dots on the top of the abdomen. During a short lifespan of one to one and a half years, she leads a boring life. She lounges in her webbed nest waiting for an insect to become entrapped in her web and lays eggs to replenish the world’s supply of more black widows. Other than that, she eats what her web catches, hangs out alone and scares everyone that sees her.

The female black widow is the most venomous spider in America. And that includes the “Brown Recluse” spider which is second most venomous. In the same quantity, the venom of the black widow is 15-times more toxic than the venom of a rattlesnake. However, that is a bit misleading since the black widow injects very minimal venom with its bite.

The bite of the black widow spider can be very painful. It can be very dangerous for small animals, babies, those with heart conditions and others with very weak immune systems. Although deaths have been recorded from black widow bites, they are very rare. The male spider has much less venom, rarely bites humans and he does, it’s barely noticeable. The black widow is not aggressive towards humans unless it feels threatened. It prefers to be left alone in its nest and bites only in self defense.

Reactions and Treatment
For Black Widow Bites

Never attempt to touch the widow. If you are working in its habitat, always wear heavy gloves to protect against bites. The venom attacks the nervous system and typically produces muscle aches, nausea and sometimes paralysis of the diaphragm which can create breathing difficulty. Although most bites do not cause serious damage it is wise to seek medical attention, particularly when affecting young children, the elderly and those with compromised immune systems.

If bitten, at first you may notice two faint red spots created by the spider’s fangs. Local area redness and swelling are likely to appear. The pain will become progressive and will travel up and down from the penetration point and will generally settle in the abdomen and back area. In more serious cases, the victim may experience a weak pulse, unconsciousness or convulsions.

Reaction and treatment. Remain calm. Try and collect the spider for accurate identification and seek emergency medical attention. Even though you likely will not be seriously affected, it is always wise to be cautious. Quickly wash the wound with soap and water. If possible, apply iodine, hydrogen peroxide or other form of antiseptic to help prevent further infection. Keep the affected area elevated above the heart level. Black widow serums are generally available at emergency rooms.

Read more about symptoms and treatment of a black widow spider bite.

Black Widow Spider’s Habitat

The black widow found in Arizona and the southwest desert states is the “Western Species” with red hour-glass on the underside of its abdomen. Most often black widows nest outside in dark, moist places like woodpiles, rock piles, wall crevices, bushes and piles of debris. In colder weather they tend to move to indoor places like sheds, garages and even inside homes. Their webs are usually closer to the ground where they can make a quick escape in case of danger.

Photo of Northern Black Widow with Red Dots on Her Back
Northern Species:
Red spots on back side
Picture of Southern and Western Black Widow with Red Hour Glass on Her Underside
Southern Species:
Hourglass on underside


She is shy and nocturnal. They spin webs that are irregular nests with silk that is typically stronger than other spiders (arachnids). She stays hidden inside the core of the nest usually hanging upside down exposing her red hour-glass belly. When active, the black widow rushes out and bites her insect victim. They have poor eyesight and often depend upon feeling vibration of an insect trapped in the web. Humans are often bitten when they accidentally touch the spider’s web sending vibrations that fool the black widow into biting a finger mistaken for an insect.

What Black Widows Eat

Like most spiders, the black widow preys on insects. Flies, cockroaches, crickets and beetles are among her favorite diets. After the prey is snared in the sticky web, she rushes out and begins wrapping the insect in silk so it can’t get away. The widow bites it’s prey and injects its venom. Either then while the widow is hungry or later, she punctures the dead insect with its fangs and injects enzymes to begin the digestive process. The widow then begins sucking out the liquid contents. The black widow herself can become prey to other larger spiders and mud-dauber wasps.

Characteristics and Breeding

She is most active producing egg sacs from May to October. Being on the prowl, the male approaches the female cautiously realizing she is bigger, more venomous and can deliver a fatal bite. He carefully reaches out with his long legs and gently touches her to see if he is welcome. If invited, he performs his function and if he is lucky, the black widow then permits him to leave safely.

She produces an egg sac that can contain hundreds of fertilized eggs. She then spins a cocoon around the sac and suspends it in the sticky web. After a couple of weeks, the young spiders hatch and begin to disperse to start their quick growth to adulthood. Few of the baby spiders survive due to cannibalism. The strongest prevail.

When they emerge, young black widows are orange and white in color. Growth to maturity takes 2 to 4 months over which time they turn to the jet black color. The total life span of the female black widow is a year to a year and a half while the male generally lives less than one year.

Getting Rid of Black Widow Spiders

Black widows like all spiders, eat insects. So the best way to avoid black widows is to rid the outside and inside of your home of infestation of insects. A quality pest control service can do this. If you are one that hates to kill even the smallest of insect life, there are natural deterrents that will keep insects away. Otherwise, call an exterminator or do it yourself.

1. Remove unnecessary debris from your yard. Things like woodpiles, discarded building material, broken down equipment and anything similar that entices black widows to take up residency.

2. Seal cracks in home walls and fences. Ivy and vines are a haven for black widows. Clear out any undesirable vegetation and keep bushes trimmed. Avoid putting plants close to outside walls.

3. Keep outside trash containers away from the house. Anything that attracts insects will likely attract black widow spiders.

4. Although infrequent, black widow spiders will take up residency inside your home. Spiders like cardboard and clutter that gives them refuge. Maintaining cleanliness inside will help deter insects which in turn attract spiders.

Pesticide Control

Relatively safe pesticides will only kill spiders on direct contact. Spraying spider egg sacs work if you crush the eggs. Unlike most insects, spiders will not absorb chemicals through their feet or legs. The best way is for you or your pest control company to search around your home where widows are most likely to build their nests every few months. When they are found, spray chemicals directly on them and sweep the webs away.

Get some advice from your selected pest control company. If you do it yourself, visit your local outlet that sells pest control products and ask service staff for recommendations of the most effective, yet safe chemicals. Never use glue traps since those also catch good friends such as lizards which keep insect populations under control.