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September 21, 2008
Black Widow Spiders: Maligned Garden Beauties
Master Gardener Column 9/20/08
As I was walking through Furnace Creek's date palm plantation on a blisteringly hot summer afternoon, I felt a light touch brushing the back of my calf. After dismissing it as a stray hair from my long, auburn, twenty-something mane, it happened again. Looking down below my walking shorts, I gasped in horror. I'd accidentally crushed a black widow spider between my foot and sandal strap. The phantom hair was silk spun by the panicked creature as it rappelled off my large leather mailbag. Gingerly removing my sandal, I was grateful I hadn't been bitten.
As a young civil servant with the National Park Service, I was on my way to collect and distribute the mail. It was my closest encounter with the black widow, North America's most venomous, nerve-damaging spider, during my five years as a naturalist in Death Valley National Park. If I'd been bitten, it would've been a two-hour ambulance ride from Death Valley to the hospital in Las Vegas.
The encounter called to mind the spider lore passed down from my Southern grandmothers - bloodcurdling tales, warning youngsters to avoid these toxic, lightning-quick creatures.
Black widow spiders are comb-footed spiders, their hind feet equipped with bristles to whip spider silk around their prey for future dining. Dr. Louis Caruana, Professor Emeritus of Texas State University's College of Health Professions, categorizes three species of black widows: the Southern, Latrodectus mactans, the Northern, L. various, and the Western, L. hesperus. Also known also as button spiders, katipo, and redbacks, they're found in temperate zones around the world, in shades of brown, black, and red. Sleek and slender, jet black with shiny spherical bodies, their almond-shaped silhouette is up to 1-1/2 inches long. Not all female widows have a red hourglass on their abdomens. It appears only in adults, is sometimes missing entirely, or appears elsewhere on their bodies. Male black widows are either solid brown or brown with white stripes and are half the size of females.
Black widow spiderlings, 1/16 inches long, about the width of a rubber band, are white or tan before molting and becoming darker. House spiders, petite relatives of the black widow, may be mistaken for spiderlings because of their shape, but are generally speckled, black, or brown.
Northern Arizona is home to the Western black widow, L. hesperus, its Latin name loosely translated "secret evening hunter." It's prudent to assume that black widows reside unseen in our gardens. Nocturnal, they set up shop in tangled webs with the consistency of cotton candy, in undisturbed places, like outhouses, eaves, garages, abandoned burrows, untended gardens, potting sheds, and loose tree bark. Normally timid, they're quick with their fangs when they or their beige egg sacs containing 100-400 eggs are threatened. Their venom, a powerful neurotoxin, may cause respiratory distress, making medical attention essential if bitten. Since they're elusive, hiding under rocks and woodpiles, it's prudent to wear gloves in the garden and become familiar with the widow's body shape and tough, disheveled web.
www.nationalgeographic.com lists the black widow's typical menu: mosquitoes, grasshoppers, beetles, caterpillars, spiders, and on occasion, the male of the species. Widows live one to three years and have their own predators: birds, bats, wasps, and frogs.
Several years ago as I stepped out onto my front porch to enjoy one of Flagstaff's timeless summer evenings, I felt the unmistakable touch of spider silk on my face. I flipped on the porch light, and there at eye level about two feet away a young female black widow was busily spinning a haphazard silken maze that would serve as home, snare, and nursery. She resided on my porch the entire summer, undaunted by my presence. I refrained from relocating or dispatching her, my insatiable curiosity overcoming my ingrained dread. When fall turned into winter, she disappeared to warmer climes, perhaps my garage, or to meet her fate with one of my garden's birds. Black widows are as effective at pest control as they are an intimidating spectral predator. Sensitive to pollution and drastic climate change, the presence of widows and their spider kin reveal our gardens' health along with that of the high country.
Freddi Steele is a Master Gardener volunteer and a former naturalist with the National Park Service. Dana Prom Smith is a Master Gardener volunteer and the coordinating editor for the Master Gardener Column. He can be contacted at stpauls@npgcable.com. For more information about the Master Gardener Program, call Hattie Braun at 774-1868 ext.17 or visit our Web Site: highelevationgardening.arizona.edu.
Posted by maxmaddy at September 21, 2008 6:52 AM