January 4, 2007 at 8:12 a.m.
A black widow is moderately sized, with a body about .5 inches long with the legs adding another inch. It is black and has a conspicuous red hourglass shape on the underside of its abdomen. The other species are very similar in appearance. However, not all species are black, some are actually brown. The hourglass markings also vary with different species, as in some species where the markings may be reduced to one or two bands. The variations within the species make it challenging to correctly identify the specific widow spider you may encounter.
Don't confuse black widow with other spiders or cobweb weavers. This very common group of spiders gets their name from the serrated bristles on the fourth pair of legs. However, this characteristic is so small that you need magnification to see it. You can usually recognize this group of spiders from their spherical-shaped abdomen and their eight eye arrangement in two rows. They also construct a tangled irregular looking web in which they hang upside down.
A black widow spider is shy and generally lives in dark, protected sites, especially near the ground. This can include logs, animal burrows, firewood, and piles of brush and stones. Sometimes webs may be constructed higher off the ground on shrubs and other plants. Egg sacs containing 200-250 eggs are suspended in their webs. Interestingly, the habit of female black widow spiders eating males after mating is not true, although it has been observed under laboratory conditions.
Black widow spiders are rare in Minnesota. The northern widow is actually native here, although it is only found in the southeast corner of the state where it is commonly found in rodent burrows. This widow is rarely discovered in buildings and it's unlikely that people will encounter this species.
Other widow species, although not native to Minnesota, are occasionally found in the state as the result of being accidentally transported here.
For example, a black widow was recently found in the Twin Cities associated with a bag of grapes. This is not the first time black widows have been associated with produce, especially grapes. Grapes may be preferred because it offers a type of cavity that black widows can use as a protected, sheltered area. The grapes are harvested and spiders are moved along with produce.
Widow spiders have been accidentally moved into Minnesota under other circumstances. A few years ago, a widow spider (probably a brown spider) was found associated with a Norfolk Island pine that was presumably shipped up from Florida. In another case, a black widow was discovered in a box of assembly parts shipped from Mexico. In one of the stranger cases from earlier this summer, a black widow was found in a mailbox. How it got there nobody knows.
People fear a black widow because of its bite. Widow venom is a neurotoxin that affects a person's nervous system. Fortunately, black widows are not aggressive but they will bite to defend themselves. Death is very rare due to a black widow bite, although the bite can be painful. The initial bite may cause a mild burning or a quick sharp pain although some people do not feel anything. You may see a small bluish red spot with a white center at the site of the bite. Symptoms include general muscle soreness, sweating, nausea, increased blood pressure, and vomiting. More severe symptoms can include muscle spasms, tremors, abdominal rigidity, and chest tightness. In extreme cases, paralysis, stupor, and convulsions can result.
Jeff Hahn is not aware of any black widow bites that have occurred in Minnesota. People usually are quick to recognize a black widow and take steps to avoid receiving a bite. However, if bitten by a black widow, the best first aid is to clean the wound and apply ice to slow down the absorption of venom into your body. Then see a physician as soon as possible so they can treat the bite. Save the spider, if possible, in case there is any doubt whether it is a black widow spider. Because comb-footed spiders are common in Minnesota, you may encounter a related spider but one that is not dangerous to people.