Venom Week: Black Widow Spiders

Male on left and female Black Widow on right

Black widow with two eggsacs

Female Black Widow on a leaf


The the United States there are 5 species of Black Widow Spiders, in Tennessee we have two species. Those are the Southern/Common Black Widow and the Northern Black Widow. They belong to the Comb-foot or Combweb family of spiders. The most commonly seen and found species of Black Widow in Tennessee is the Southern Black Widow. The Northern Black Widow is a rare find due to the fact that they prefer to live in tree limbs high up away from humans.

females of both species of spider can reach up to 1 1/2 inches with their legs extended, and typically the Northern Black Widow is larger than the Southern, but both can have an abdomen over a 1/2 inch in diameter if their food supply is plentiful. The males are typically smaller in size that the female and this goes for both species.

Both species of spider have 8 eyes that are arranged in two rows of four eyes, and even though they have 8 eyes their vision is poor. Their bodies appear to be hairless and glossy to the naked eye, but they are actually covered in dense fine hairs that they use to "see" on their web. Their colors can vary from a deep black, brown and even a reddish brown and their legs can appear to be striped with red and black, or reddish brown and black.

On their belly, underside, they have a red or orange hourglass. Most will have a red dot on their bottom above their spinnerets. It can be clearly seen against their dark bodies, and it is their distinguishing mark. This vibrant mark tells birds, lizards, and other predators that they are venomous. Meaning, "Hey I pack a punch back off!" They do have natural predators in birds and lizards. In juveniles this distinguishing mark can be white or another color or missing completely.

Males of both species are considered harmless to vertebrates because of the shortness of their fangs. They do carry venom but cannot really get a good bite because their fangs are short. There have not been a case of a human being bit my a male Black Widow reported ever. The males are about half the size of the females and can have red or yellow spots or bands on their back and sides. These spots can be circles or diamonds in the red color or in yellow, and they may be in a row.

In nature the spiders prefer to live under bark, logs, in rocky places, under shrubs and in trees, places that are typically dry and safe. Places that are not disturbed often. Us humans have provided plenty of safe places for the widows to thrive. They can be found in out buildings, sheds, abandoned homes and barns, boxes, attics, crawl spaces, rubbish piles, root cellars, seldom worn shoes, pretty much anywhere that is dark and quiet.

Their webs are non-symmetrical, irregular mesh webs.They are usually built in corners, ceiling edging and other places with nooks and crannies. Often in the top of the web they will have a retreat for them to hide in and it is often funnel like in shape.The Northern Black Widow's retreat is often on the end of tree branches and is dome like in shape, the rest of her web will spread out from her dome retreat covering the rest of the branch.

Black Widows stay in their retreat unless their web is disturbed. When their web is disturbed they will race out to the section of web that the prey is on with surprising quickness. They are highly aware of their surroundings even though they have poor eyesight. Usually if something larger like a bird or a human disturbs their web they will not attack, but retreat into their hiding place, or escape the web.

Black Widows a formidable hunters. They will kill anything from the size of a housefly up to a scorpion which is many times larger than they are. They will not eat prey that has not been treated with several bites of venom. Their venom breaks down the prey's insides till it's juice that they can suck out. They wrap their prey in silk to subdue it and when they are finished with their meal they leave an empty husk in the silk. They will bite their prey several times before they will consume it.

In mating is where the Black Widow gets her/his name. It is thought that after the mating is done the female will eat the smaller male. In a study done with 18 males only two of the males were actually eaten by the females. So they have a pretty good chance of surviving the mating. These two males that were eaten were actually on their "second date" with the female, after they had mated a second time they were consumed. This goes to show that it is always smart to feed your date before you get down to business. Males can actually mate with several females in a season.

How the males gets such a deadly female to mate is simple, he "blinds" her by cutting her web in places and he vibrates his abdomen to put her in a trance. He vibrates for about an hour before he even attempts to mate her. If he fails the first time he cuts more of her web and starts all over. (a vibrating male is every woman's dream, too bad a spider gets that wish filled.)To ensure his safety he uses his webbing to form escape webs. He can use the to get out quickly if she rejects him. As every male he has a back up plan. Before he mounts her he will weave a silk web around the female. This web is called a "Bridal Veil", romantic huh? This veil will subdue her for a few seconds should things go wrong. Once he has inserted his pedipalps into the female to inseminate her this is the most dangerous time for him. If the female attacks while mid insemination he will need a few extra seconds to withdrawal himself. Hence the Bridal Veil, it should give him the extra time he needs to escape before he his turned into lunch.

The Black Widow spider can produce 5 to 10 eggsacs, and each eggsac can have anywhere from 150 to 250 eggs inside. The baby spiders or spiderlings will hatch in the eggsac and molt before they emerge about 4 weeks later. Newly freed spiderlings are cannibalistic, and do not stay together. They balloon off (like in the end of Charlotte's Web where the spider babies leave Wilbur).The spiderlings are harmless to humans at this age due to their size, and they can easily slip through a window screen (they are tiny!)

Now the part we all dread, the bite. Usually the actual bite is painless. The pain will arrive 8 hours later with no skin lesions, that is of course after it has be circulated through your system. That means that you may not even be able to see the sight of the bite. Pets are extra sensitive to their venom a will have a bite area with a white/blanched section with red surrounding it, this is often called a "red zone". 90% of all cats that are bitten die.

In humans the symptoms of a bite from a Black Widow is pain in the legs, sides, thighs and chest and this pain is often mistaken as renal stones,acute appendicitis,m or acute myocardial infarction. Other symptoms are sweating,diphoresis, nausea, and vomiting. The actual degree of the symptoms range due to victim age, sensitivity to venom and how much venom was injected.

In a study from 1960-1969 only four deaths were caused by Black Widow bites. The number of bites has actually dropped due to the widespread used of indoor plumbing. Who knew that an outhouse an ideal spot of spiders?? Anyway, to prevent getting bitten use a vacuum to suck up their eggsac's and the spiders and dump them far away from your house, like in the woods somewhere. The State of Tennessee recommends use of sticky boards near windows, doors, and any entry point into a structure, and of course wearing protective clothing when cleaning in un-used area's like behind shutters. Protective clothing is a hat, long sleeved shirt, pants, boots and gloves. Use tape to seal your cuffs of your pants and shirt to ensure that no spiders can get in your clothing.

If in doubt call a professional. Hey it may cost a few bucks, but it may save you some pain in the end. And remember NEVER to handle a spider bare handed unless it's a daddy long legs, those are okay. And please use this info to educate your kids on spiders and snakes. I tell mine to never touch a spider or snake, but to get mommy or daddy. That's what were for, killing of scary things.