Itsy bitsy? Sure, but spiders loom large in hiker phobias. They shouldn't: Only a few subspecies of the black widow and brown recluse can inflict enough damage to cut short a hike. Here's what you need to know about North America's most venomous spiders, from how to avoid them to treating their bites.
Ranging from southern Canada to Mexico, five species of black widow crawl across North America—inhabiting every state except Alaska. The dangerous female is shiny, black, and about an inch-and-a-half long when her legs are fully extended from her lightbulb-shaped body. The characteristic red pattern on the underside of her abdomen is hourglass-shaped, with slight variations in subspecies. Males have smaller bodies and are an inch long when their legs are extended, and their coloration is also more variable: They can be black, brown, or gray, and, if they do have an hourglass marking, it’s typically yellow or white. Though both sexes will bite in self-defense, beware the femme fatale. Males aren’t venomous, but the female’s neurotoxin is 15 times more powerful than a rattlesnake’s and causes debilitating pain. Fortunately, the dose is small and very rarely deadly (see “Venom Science,” next page). Black widows nest close to the ground in irregular silk tangles; they build small, offwhite webs and hide from predators in tunnels they weave or in nearby nooks incorporated into the web. Beware of them in outhouses, and under logs and rocks when you’re setting up camp.
BROWN RECLUSE Not always their namesake color—they can be light yellow to reddish—brown recluses have solid coloring on their legs and abdomen. These quarter-size hunters’ most famous marker is a dark brown violin shape directly behind the eyes, but this “fiddleback” pattern fades if an individual has molted recently—and it’s also a trait for two non-venomous spiders. To make a positive ID, focus on a trapped (or dead) spider’s eyes: Almost all other species have eight, but recluses have six in a semicircular set of three pairs. Misidentification causes massive over-reporting of brown recluses—and their bites—says Rick Vetter, a University of California arachnologist. If you’re outside their native habitat, encountering a brown recluse is unlikely. Within their range, they thrive in human-altered environments like sheds and old houses. In camp, watch for them when moving rocks and collecting wood. By day, these hunters hide in small, irregular webs spun in dry, dark corners, but they emerge at night to scavenge and hunt. Because of their delicate carapaces, they avoid live prey and eat mostly dead insects so they’re not injured in a fight.
Assess the Risk
Experts agree that the chance of being bitten by a brown recluse or black widow is low, and the risk of death is almost nil. Even before antivenin, a black widow’s tiny injection killed fewer than five percent of victims. Nationwide, the average annual spider-related death rate is less than four people, most of them children. That said, collecting wood, using an outhouse, or moving rocks from a wouldbe tent platform can increase your risk of a painful—but very unlikely fatal— arachnid encounter. Within hours of a bite, a brown recluse nip can cause an ugly ulcer; a black widow bite may cause excruciating abdominal cramps.