The black widow spider (lactrodectus) belongs to a group of spiders commonly known as cobweb spiders. The characteristic hourglass is located on the underside of the abdomen. Female black widow spiders are dangerous with a spider bite that can inject toxic venom. Black widow spiders build webs between objects, and bites usually occur when humans come into direct contact with these webs. A spider bite from a black widow can be distinguished from other insect bites by the two puncture marks it makes in the skin. The venom is a neurotoxin that produces pain at the areas of the spider bite and then spreads to the chest, abdomen, or the entire body. The female black widow spider bite is especially dangerous for humans because of its unusually large venom glands; however, black widow spider bites rarely kill human beings if they are give appropriate treatment.
We have identified a spider bite ointment that contains activated charcoal along with other spider bite treatments. We have also located a spider bite first aid kit that includes the spider bite ointment along with supplies to deal with the other symptoms associated with venomous spider bites (e.g., brown recluse spider and black widow spider) and other insect bites and stings.
Female black widow spiders are about ½ to 1 ½ inches with legs spread. They are normally shiny black, with a red hourglass marking (see photo) on the underside of the abdomen. The abdominal marking on a black widow spider may range in color from yellowish orange to red and its shape may range from an hourglass to a dot.
Male black widow spiders are similar in color to the females but are usually half the size of the female black widow with smaller bodies and longer legs. Male black widow spiders typically have yellow and red bands or spots on their backs (see male photo to the right)
Juveniles of either sex resemble the males in markings and size. Young black widow spiderlings are off-white in color and gain more color as the mature (see imature female photo to the right)
Only mature female black widow spiders are venomous; males and juveniles of either sex are harmless to humans.
There are five species of venomous widow spiders indigenous to North America:
Latrodectus moctans, the black widow spider, sometimes called the southern black widow (warm reagions of USA)
Latrodectus bishopi, the red widow spider (Florida)
Latrodectus hesperus, the western black widow spider (Western North America)
Latrodectus various, the northern black widow spider, (most of USA and SE Canada)
Latrodectus geometricus, the brown widow spider (warmer regions of the USA)
From left to right, these are: the red widow spider, the western black widow spider, the northern black widow spider, and the brown widow spider.
There are several species of round-bodied, web-weaving spiders that are sometimes confused with the black widow spider. Considering the harm that can be caused by female black widow spiders, it is important to be able to distinquish them form these other commonly mistaken species of spiders:
From left to right, these are the false widow spider (Steadota), the common house spider, the argiopie spider, and the orb weaver spider. These are harmless to humans and cannot inflict venomous spider bites like the female black widow spider. Of course the most distinquishing feature of the black widow spider is the red, orange or yellow hourglass mark on the belly.
Like most cobweb spiders, black widow spiders feed mostly on insects caught in their webs. The black widow spider web is strong but irregular in shape and pattern. Adult male black widow spiders do wander in search of females, but cannot bite humans. Most black widow spider bites to humans occur by accident when I a human comes into contact with a web with a female black widow.
As the name implies, the female black widow spider may occasionally kill and eat a male black widow after mating but this is not typical behavior.
Over the course of a summer, the typical female black widow spider can lay literally thousands of eggs in large egg sacs suspended in their webs. However, less than a dozen usually survive the 2-4 week incubation because of cannibalism.
It takes about 3 months for black widow spiders to mature. After maturity, female black widows live about 6 to 12 months, male black widows typically only live a month or two.
Black widow spiders are found throughout North America, but are most common in the southern and western areas of the United States.
The black widow is commonly found in the following places:
Outdoors - black widow spiders can reside in undisturbed areas or places where debris has accumulated such as woodpiles, rubble piles, under stones, in hollow stumps, and in rodent burrows, privies, sheds under eaves, and fences.
Indoors – undisturbed or cluttered areas such basements, crawl spaces, garages, storage rooms and sometimes behind furniture or boxes are common locations for black widow spiders indoors.
Other - black widow spiders may also be found in places where prey insects are plentiful.
Take the following steps if you have a black widow spider bite:
If safe, capture the black widow spider. Because it is nearly impossible to identify the cause simply by examining the wound and because systemic symptoms can result from a variety of causes in addition to black widow spider bite, identifying the spider will help the medical professional better know which course of action to take.
Black widow spiders may be distributed throughout the house and infestations may take months to bring under control. The best control for black widow spiders uses multiple techniques involving spider bite prevention, cleanliness, trapping and insecticides. Individuals can take the following steps to minimize risk of black widow spider bites:
Inspect or shake out any stored clothing, shoes, or equipment before use.
Minimize the empty spaces between stacked materials.
Dust and vacuum to remove black widow spider webs and egg sacs.
Eliminate garage, basement, attic and closet clutter.
Remove and reduce debris, rubble, and tall grasses from around the house.
Take care when handling cardboard boxes where black widow spiders like to build webs.
Keep your tetanus booters up to date (every 10 years). Black widow spider bites can become infected with tetanus spores.
Control black widow spider and prey insect populations in the home with pest control products such as dusts, sprays and traps, preferably with natural products that are not harmful to humans, pets or the environment.