Black Widows

I encountered my first black widow spider when I was about seven years old. The house where I grew up in Missouri had a basement that only extended to within about 15 feet of the front of the building; that last 15 feet was a dirt-floored crawl space. There was a door leading into it from the basement proper, and just inside the door the dirt had been excavated to the level of the basement floor in a ten foot square "room" we called the "coal bin hole". There was a small door through the foundation there, and back in the days when the house had been heated by coal, that was where the coal was unloaded. I often explored the coal bin hole to see what kind of bugs I could find, but one day I was shining a flashlight into one of the corners, and there was a big, fat black widow in its web. I'd heard plenty of horror stories about black widows, and I quickly retreated; it was a couple years before I got up enough nerve to go into the coal bin hole again!

I always seem to picture black widows in such places, even though most of the other widows I've found have been in the outdoors. I have found them in woodpiles and under rocks. In Montana, I was doing landscaping at the cabin that was our first dwelling there, and found five different widows under the round river rock I was picking up from around our 20 acres to use to line the parking area. In Missouri, I've found a few in out of the way corners in barns and sheds. But really, they don't seem to be all that common in most of the places I've lived.

There are five widow species in the U.S., though more than 30 species in the genus are spread across the world. The most common species in Missouri is the southern black widow, Latrodectus mactans, though the northern black widow, L. variolus, is also widespread across the state.  The spiders I encountered in Montana were western black widows, L. hesperus--their appearance is very similar to southern widows.  The red widow, L. bishopi, has a dark brownish or black abdomen with a red spot that is often a triangle on the underside and various red spots with yellow borders on the back and sides, and reddish brown cephalothorax (head portion) and legs.  The brown widow, L. geometricus, has a brown body with the typical red hourglass on the underside of the abdomen, and legs that are banded with dark and light brown.  The northern black widow is found across the northeastern quarter of the U.S. as far north as southern Canada and south to Missouri.  The southern widow is found across the South and Southeast from Arizona to Florida, and north to Missouri and Virginia.  The western widow ranges from British Columbia to Mexico and as far east as Colorado.  The red widow is confined mainly to Florida, and the brown widow is a tropical and subtropical species that was not native to North America but now has established populations across the southern tier of states.  All these species have similar venom and body shape, and are found in similar habitats. 

Black widow males are no more than 1/4th the body size of adult females, but have longer legs and more colorful bodies, with various white, red, and yellow stripes and spots.  

In the wild, black widow habitats are crevices in and beneath rocks and logs, holes in embankments, and other dark, sheltered areas.  But they readily use human structures, including sheds and outbuildings (and outhouses!), water meter holes (I'm always concerned when I lift the cover off the valves in my irrigation system at our place in Montana, and so are the guys that service the system), and under any large object that has been undisturbed for a while.  They are seldom found indoors in houses, but occasionally will come inside as cold weather descends.  Perhaps the one widow I found all those years ago in the coal bin hole came in during the autumn.

One of the most famous characteristics of black widows, and where they get their name, is that the female kills and eats the male after mating.  However, according to most authorities this seldom happens in the wild; it was observed in captive situations where the male had no chance of escaping.  Females build haphazard three-dimensional webs with little structure other than a dense area to the rear where the female hides.  The male enters the web and mates with the female, and then at least attempts to escape.  Males also often dismantle portions of the web, tearing them apart, rolling the silk up, covering it with their own silk, and removing it from the vicinity.  This is believed to be for the purpose of removing the scent of other males from the area in order to monopolize the female; females will mate with several males, and can produce up to nine egg sacs in a summer, each with an average of 400 eggs.  The spiderlets are very cannibalistic, and few survive the two to four months to maturity.  Adults are preyed upon by mud dauber wasps.

While black widow webs are far from artistic, the silk ranks among the strongest of all spider silk.  Like most web-building spiders, the female lurks in the rear of the web, waiting for vibrations to signal that a prey insect has entered--widows have very poor eyesight.  The female then quickly emerges, bites the prey, and holds it tightly.  The venom takes about ten minutes to take effect, and and when the prey stops moving, she releases digestive enzymes into the bite wound and carries the insect back to her retreat before feeding.

Unlike brown recluse venom, the venom of Latrodectus species is a neurotoxin, and the effects are quite different from the tissue damage that recluses are famous for.  Widows are reluctant to bite, and people usually get bitten when the spider is pressed against the skin, often by reaching under objects where the spider is found.  Putting hands in gloves that have been sitting undisturbed, or feet in boots that have been sitting for a while, is another good way to get bitten.

The southern black widow is reputed to have the most potent venom, while the brown widow has the least severe bite symptoms--it may not be dangerous at all.  Often the bite will be dry, with no venom injected, and the severity can vary due to the amount of venom injected.  A bite may first be felt only as a pinprick as the extremely small amount of the potent venom is injected, but quickly swelling and redness around the bite appears, and in one to three hours there is severe pain which often moves through the body and settles into the back and abdomen.  Intense muscle and abdominal cramping can last for more than 48 hours.  Nausea and profuse sweating are common, along with chills, fever, headache, and severe high blood pressure.  Tremors, convulsions, and unconsciousness can happen with untreated bites, and if death does occur it will be due to suffocation.

Treatment of black widow bites usually consists of treating the symptoms.  There is an antivenom available, but it is usually only administered to those at highest risk, such as young children, the elderly, or those with heart conditions. Victims usually recover within two to five days.  Deaths are rare; about 2,600 black widow bites are reported in the U.S. in an average year, resulting in 7 deaths.