The Black Widow Spider

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Black Widow Appearance

The black widow is the most dangerous spider in Utah. Found all over the United States, widow spiders can come in several different forms. The species of widow spider most commonly found in Utah is Latrodectus hesperus, or western black widow. The western black widow is part of the Theridiidae, or cobweb spider family. This family includes over 3,000 different species, only a few of which are considered “true widow spiders.”

Western black widows, as well as the other true widow species, are all extremely venomous, and their bites have the potential to cause fatal injuries. Many other cobweb spiders are known as false widows because of their similar appearance to true widows, which is why being able to identify a true widow is crucial. Understanding as much as possible about the western black widow in Utah is of the utmost importance, as this knowledge could potentially save your life.  


Both female and male widow spiders have different colors and markings when they are in immature stages of development. They will both be a lighter color, with orange, red, or yellow markings on their abdominal area that could either be in round or striped formations. As the female gets older, it will begin to take on the shiny black color it is known for, and the famous red hourglass shape will develop as she becomes fully mature. Mature males will have slender bodies that are only half the size of mature female bodies, and they will maintain their lighter brownish color and unique markings throughout their short lives. Though spotting a male means that a female is likely close by, the males are generally harmless compared to the feared females.

Female Western Black Widow Characteristics

  • About ⅓ of an inch in length
  • Two rows of four evenly sized eyes
  • Relatively small fangs
  • Disproportionately plump abdomens
  • Shiny, solid black color
  • Red hourglass shape on underside of abdomen
  • Usually, no markings other than the hourglass
  • Hourglass may not be connected in the middle

False widow spiders will lack the hourglass-shaped marking, and they will likely be a lighter color as compared to the dark black of a true black widow. Never take any chances if you have been bitten by a spider that at all resembles a black widow. Always seek medical attention!

Life Cycle

Widow spiders are cannibalistic, especially in these early stages of life. Though hundreds of eggs may be hatched in the sac, the majority of them will die and/or be cannibalized by their siblings. The mother spider will occasionally eat her offspring for sustenance, but it has also been theorized that a mother widow spider will eat the larger or more aggressive spiderlings in order to prevent them from killing all the other spiderlings.

The mother lays hundreds of eggs that are sheltered in a yellowish sac attached to the nest.  ➥  Eggs hatch roughly two weeks after being laid.  ➥  Spiderlings remain in the sac through their first molt.  ➥  Spiderlings then use strands of silk to catch air currents and be carried away from their mother when they are ready.  ➥  The spiders continue to molt and mature as they look for shelter and food on their own, reaching full maturity within six months.  ➥  Males will only live a few weeks or months, and they spend their lives looking for a mate.  ➥  Females can live up to three years in optimal conditions, but most die after only one year.


When it comes to understanding the terrifying reputation of this spider, you do not need to look any further than the name, “black widow.” This moniker is derived from the idea that female widow spiders always cannibalize the males after mating. While this is an observable habit of black widow spiders, males often get through the process without being harmed, especially if the female has recently eaten.

The courtship begins when the male approaches the female’s web and taps on it with its legs. The tapping performed is a type of “dance” that sends vibrations through the web that are then felt by the female. If the female is receptive, she will also tap the web in response. The vibrations created during this ritual are unique to each species of widow spider. After receiving the vibrations back from the female, the male will cautiously approach the female and lightly touch her with his legs. If the female allows the touching, mating will begin.

Aside from mating rituals, there are several notable habits of western black widows.

  • They weave erratic and asymmetrical webs.
  • Making vibrations on their webs is believed to be a form of communication.
  • Western black widows prefer to be left alone in dark, isolated areas.
  • Neglected bushes and shrubbery are ideal locations for their webs.
  • They will live in any undisturbed area, including basements, garages, and attics.
  • The female rarely wanders far from her web throughout her life.

How Dangerous Are They?

Western black widow spiders do not always inject venom when they bite. In fact, a venomous bite usually only occurs when the spider is physically touched and feels its life is in danger. A non-venomous bite will sting the flesh and become irritating, but it is not likely to cause any significant harm. However, when the black widow does inject venom as it bites, the initial feeling is much more intense and painful.

True widow spiders produce a neurotoxin that affects muscle function and the nervous system. In severe cases, an intense burning sensation may be felt by the victim, followed by pains in the chest and abdomen. Other symptoms may include excessive sweating, fever, and nausea. In rare cases, victims may experience hallucinations, muscle spasms, and swelling of their extremities. The most extreme result of a black widow spider bite is death, but this is highly uncommon, especially if medical attention is immediately sought. Symptoms most often last from days to weeks, with varying levels of severity and duration.

Thankfully, black widows do not want to be disturbed and will only bite humans when they are touched or physically disturbed. There are easy steps to take in order to avoid being bitten by a western black widow spider in Utah.

  • Be cautious when dealing with unruly vegetation.
  • Turn on the lights, and look where you are stepping and reaching.
  • Use a ladder instead of blindly reaching for high shelves or cabinets.
  • Wear thick gloves when working in the garage, basement, attic, or even just the yard.
  • Examine old clothes carefully before wearing them.
  • Regularly clean and inspect all of your property.

Call Holmes Lawn & Pest at (801) 616-5296 for the best pest control in Utah.

Thank you for reading our article, for more informative articles on the common spiders found in utah, feel free to give our last on the woodlouse spider and our newest article on the camel spider a read through.

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