Beware of black widow, brown recluse spiders

Black widow spider

MARYLAND is home to numerous species of spiders, but only three are considered especially poisonous to humans: the southern and northern black widow spiders and the brown recluse. Other spiders can inflict strong bites or inject small amounts of venom to cause a rash or hurt like the sting of a hornet, but their bite is not considered to be especially hazardous.

Courtesy Photo

There are nearly 50 species of widow spiders found throughout the globe, except the polar regions. The black widow spider gets its name from its jet black color and the habit of the female eating the male soon after mating.

Female black widows are much larger than the male; they are black with a distinct red hourglass mark on their belly. Male black widows can be black, brown or gray, and their hourglass marking can be red, yellow or white. The female is the size of a quarter and has much more venom than the male. It is the female that is the most deadly of the widows.

Black widows are normally not found indoors; they prefer areas like porches, tool sheds, garages, basements and firewood piles. The black widow constructs a fairly large web, and the female is often spotted hanging in such a way that the hourglass mark on her belly is very noticeable.

The venom of the black widow contains the chemical latrotoxin, which is a neurotoxin. Being bitten by one causes an illness known as latrodectism. Some symptoms of latrodectism include severe pain in the muscles, cramping, fever, increased heart rate, headaches, dizziness, vomiting, rashes, swelling and erratic behavior.

In some cases, the symptoms of black widow poison can be much worse, especially if a large amount of venom has been injected into a child, elderly person, pregnant woman or someone who is very sensitive to the poison.

Severe symptoms can include renal failure, spontaneous abortion, shock, coma and death.

Brown recluse spiders

The brown recluse is a large uniformly brown hairless spider that has a distinct violin shape on its back; it's classified as a species of fiddle-back spiders. Both the male and female are about the size of a quarter. Brown recluse spiders are more common to the Midwest, but they are now considered to be residents of Maryland.

Like its name, this spider likes dark, undisturbed sites and is more prone to live in a house than the black widow. It has more nocturnal habits and can be found in attics, basements, ductwork, closets, boxes, barns, garages, sheds and wood piles.

The web of the brown recluse is not very large; it catches much of its prey by being quick and stealthy. The hemotoxic venom of the brown recluse kills tissue near the site of the bite.

The bite can cause a stinging sensation, rash, swollen areas around the bite mark, and blistering, generalized itching, fever, nausea and restlessness. In severe cases, the venom can cause, large lesions of dead skin, large bruises, fever, chills organ failure and shock, but rarely death. The young, elderly and those with sensitivity to the venom are most at risk for a severe reaction.

If you feel like you've been bitten by a poisonous spider, it's a good idea to get the spider, even if it's squished, and take it to the doctor or hospital. There are some antivenins, steroids and other medications that can be employed to counteract the venom.

The best courses of action are to be careful where you reach and to wear gloves whenever you are handling firewood or reaching into someplace you cannot see.

Nature Notes for 7/31/2011