Araneae: Theridiidae, Latrodectus mactans
The male black widows abdomen is more elongate than that of the female, with white and red markings on its sides. The females abdomen is almost spherical, usually with a red hourglass mark below or with 2 transverse red marks separated by black. The legs of the male are much longer in proportion to his body than that of the female. The female is the most easily recognized, her shiny black body giving great contrast to the red hourglass marking on her round abdomen.
The black widows range is from Massachusetts to Florida and west to California, Texas, Oklahoma and Kansas. Although they can be found in almost every state (and some portions of Canada), this spider is most common in the Southern locales of the United States. Black widow spiders are common around wood piles, and are frequently encountered when homeowners carry firewood into the house. Also found under eaves, in boxes, underneath unused construction materials, inside wooden toy boxes, firewood boxes, outdoor toilets, meter boxes, and other unbothered places. These hiding places for spiders are very important in inspecting or treating in a black widow spider control program.
The female black widow spider rarely leaves her web. The web she constructs is an irregular, tangled, cris-cross web of rather coarse silk. The core of the web is almost funnel shaped, woven into a silken tunnel in which the female spider spends the majority of her daylight hours. This web is altered and rebuilt in a regular basis and is capable of capturing rather large insects. The female wraps any captured prey with her silk, repeatedly turning her victim with her legs as she applies more silk. After her victim is covered in silk, the spider kills her prey by injecting her venom. The prey might be eaten immediately or reserved for a later feeding. After the prey is fed upon and the body fluids are sucked from the victim, the carcass is cut loose and allowed to drop to the ground. The female black widow is most often found hanging upside down in her web, where she spends most of her daytime hours. She stays close to her egg mass, defensively biting anything that disturbs her or her egg sac. After laying her eggs, the female black widow is hungry and more likely to bite a human. The female black widow stores sperm, producing more egg sacs without mating. Some females live more than three years.
Egg sacs are pear shaped (or oval), brown, papery and about ½ inch long. They hold from 25 to 900 or more eggs, which have an incubation period of 20 days. The spiderlings disperse shortly after emerging, tearing an opening in the egg sac and stay near the sac. After several hours, these second instar spiderlings balloon to the ground and scatter. Growth requires two to three months, with older females dying in autumn after egg laying.
Of all spiders, the Black Widow is the most feared. The females venom is especially poisonous to people. Despite its reputation, this spider often attempts to escape rather than bite, unless it is guarding an egg mass or if it is cornered and pressed. The male black widow will not bite you. After mating, the female sometimes eats the male (remember, she only has to mate once in her life), earning the name "widow." During the period shortly following mating and laying of eggs, the female black widow can be a little cranky and hungry. After this period (if he lives through it!) the male lives quite comfortably, eating prey captured by the female. The development of his venom sacs stop and become inactive as the male matures, thus making him less of a potential problem than his female counterpart.
The bite of the female black widow spider may not always be felt at first and besides slight local swelling, there is usually little evidence of a lesion. Two tiny red spots can sometimes be observed in the center of the swollen area. Most of the time, pain at the site of the bite occurs immediately and becomes most intense after about three hours. An overall aching of the body, especially the legs, are common reactions. Headache, elevated blood pressure, nausea and profuse perspiration may occur in severe cases. The condition is self-limiting and in most cases symptoms disappear in two or three days. Calcium gluconate is used intravenously to relieve and relax muscle spasms produced by black widow venom.
Be very careful when working around areas where black widow spiders may be established. Take proper precautions, wear gloves and pay attention to where you are working. Black widow bites are sharp and painful, and the victim should go to the doctor immediately for treatment. For more about control of the black widow spider, go to Spider Elimination.