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About the cover

  D e s e r t   E x p o s u r e    August 2008

What's Bugging You?

A field guide to the creepy-crawlies around — and sometimes on — us here in Southwest New Mexico.

By Peggy Platonos



"What do you think about our New Mexico bugs?" asked a friendly neighbor, shortly after I moved into the house I'm renting in the semi-wilderness of the Mimbres Valley.

A tarantula, found outside the author's house in the Mimbres Valley. It had a legspan of five or six inches.
(Photo by Peggy Platonos)

Honestly, I hadn't given much thought to bugs. As a newcomer to New Mexico, I was more concerned about potentially dangerous critters like rattlesnakes, javelinas and mountain lions — none of which I had ever encountered in suburban New Jersey, where I grew up, or in London, where I lived for seven years, or even in upstate New York, where I had enjoyed a pleasantly rural existence for the last three-and-a-half decades.

I wasn't even all that concerned when my landlady warned me, emphatically, never to pick up a rock without rolling it over first to be sure there wasn't a black widow spider lurking under it. I wasn't sure what a black widow spider looked like, but I figured the thing to do was simply to avoid any spider found lurking under a rock.

It wasn't until I discovered that there were spiders of all shapes and sizes lurking inside my house that I began to feel alarmed. Then I heard about brown recluse spiders and the horrors that can be unleashed by their bite, and I succumbed to a full-blown case of paranoia, viewing every spider as potentially dangerous.

Apparently, I am not alone in this. "Part of the problem we as biologists have is misnomers and misconceptions about what is dangerous," says Dennis Miller, professor of biology and department chair at Western New Mexico University in Silver City. "One of the big things you need to know is there's a big difference between an animal being dangerous and being venomous. All true spiders are venomous. Their venom is a form of digestive enzyme that is injected when they bite. But there is only one truly dangerous spider in this area: the black widow spider."

But even the danger from the bite of black widow spiders may be overrated, says Dave Richman, associate professor and arachnology specialist at New Mexico State University in Las Cruces, as well as curator of the Arthropod Museum. "I think there's way too much fear," he says. "I'd like to put the record straight. According to the Centers for Disease Control, black widow spiders have not caused a death in the United States in the past 10 years. There's far more danger of death on our highways, or from bee stings, or even in bathtubs. Grizzly bears beat out black widow spiders, too, by killing half a person a year — well, one person every two years."

Male black widow spiders are smaller than the females and have smaller fangs, which deliver smaller doses of venom and are nearly incapable of biting humans. "It's the female black widow spider that is the dangerous one," Richman says. And those females don't hesitate to bite people when they feel their lives or egg sacs are threatened.

"There were a lot more bites in the past because of outdoor toilets," Richman explains. "Female black widow spiders would hang out under the seats, which were, from their point of view, a boon. A food supply in the form of flies was readily available, and the seats provided a sheltered place for egg sacs."

Richman has personal experience with the effects of black widow spider bites. His young daughter was bitten three times while in her bed when she was about 10 years old by a black widow spider that became trapped in her clothing. "The venom does make you agitated. It gives muscle cramps, sometimes a light fever. But a healthy person is not likely to die," Richman says. The treatment, he adds, consists of "giving painkillers like Advil or ibuprofen to lessen the muscle pain and bring down the fever. The symptoms last a couple of days, and there are no after-effects."

The bite of the brown recluse spider, however, is a different story. "A brown recluse spider sore stays painful for quite a while," Richman says. The spider's venom begins to "digest" the flesh around the bite, causing the cells to become necrotic — in other words, to die. "Normally, a bite produces a sore about the size of a quarter. There are, however, a number of conditions that can cause similar symptoms: for instance, Lyme disease or the early stage of syphilis. A misdiagnosis is dangerous, because the treatment regimen may be completely different."

Some nasty results of a bite by a brown recluse spider have nothing to do with the spider's venom, Richman adds. "The bite can also cause various kinds of infections by introducing bacteria into the wound, including flesh-eating bacteria. This is why brown recluse spider bites are treated with antibiotics — not to deal with the venom, but to deal with any bacteria that might accompany the bite."

Despite reports of bites by these spiders in our area, there have been, according to both Miller and Richman, no confirmed specimens of brown recluse spiders found in this part of New Mexico. This good news is tempered, Richman cautions, by the fact that "we do have a very similar native species that produces the same sort of bites. I doubt that the average person would notice the difference between either the spiders or the bites."

He is referring to the Apache violin spider, which can be found pretty much all over the southwestern part of New Mexico and the southeastern part of Arizona. Both brown recluse and Apache violin spiders are members of the "violin" spider family — a name that refers to the violin shape commonly found on the cephalothorax (the front segment) of these spiders. Both species are quite small — their bodies about a third of an inch long and their overall length, including leg span, about an inch. (Males are a little smaller than females.) They have six eyes instead of the eight that most spiders have. (Unless you're young enough to have exceptionally sharp vision, you would probably need a magnifying glass to count the eyes.) And their venom is similar, too.

Fortunately, neither brown recluse nor Apache violin spiders are particularly aggressive, at least toward humans. "They seldom bite," Richman says. "Usually only as a last resort if caught in clothing, for instance."



Years ago, I came across this statement about snakes in a little children's book: "Only a few kinds of snakes are poisonous, but they've given all snakes a bad name." The same can be said about spiders. Taken as a whole, spiders are actually an interesting bunch.

"All have eight legs and most have eight eyes," Richman says. "And they have silk glands in the abdomen and spinnerets (usually six) for making webs. The spider silk they produce, known as 'gossamer,' is quite strong. Young spiders sometimes travel by 'ballooning' — spinning a long thread, hanging at the end of it, and letting the wind blow them to a new location."

Instead of indiscriminately slaughtering spiders we find in our homes, we probably should welcome them, because they tend to dine on the kind of smaller insects we're happy to see disappear: mosquitoes, flies, gnats, ants. There are even some kinds of spiders that are sworn enemies of black widow spiders. One that is native to this area is the daddy-longlegs spider (also called the "cellar spider") — not to be confused with the gangly, round-bodied daddy longlegs that is more common on the ground and quite harmless.

I have a lot of the latter running around my house, too, and I leave them alone. They are not actually spiders, although they do have eight legs and are arachnids, but belong to a separate order. "They use the second pair almost like antennae," explains Dr. Carol Sutherland, Cooperative Extension entomologist at NMSU. The body of these traditional daddy longlegs is a single roundish unit, whereas all spiders, including the daddy-longlegs spider, have two body segments — the cephalothorax in front and the abdomen behind.

According to Richman, native spiders in this area, including the daddy-longlegs spider, are rapidly being replaced by the imported Mediterranean squint-eyed spider. These newcomers not only don't like black widow spiders, they don't like any other spiders, and are losing no time in getting rid of them. "As one of my friends in California said, 'They're simplifying the ecosystem,'" Richman comments.



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