Don’t be alarmed, but they may be hiding out in a corner near you—clinging to the dark, cluttered, or unfinished nooks of homes, crawl spaces, and sheds, or the tangles of last year’s firewood pile. Anywhere they can rest in darkness until the sun sets. But black widow spiders aren’t waiting to pounce on you. Probably they could care less about humans—being much more interested in their next bug-based meal. I’d even argue these complex, misunderstood creatures are worthy of a little arachnophilia, once you get to know them.
Western black widow spiders (Latrodectus hesperus) are found in arid regions around the west and plains. The scientific name is a little dose of poetry as Latrodectus is a mix of Latin and Greek for bandit-biter and hesperus is a nod to the western evening star (“biting bandit of the western evening star,” maybe? How beautiful is that?) There are more than 30 species of widow spiders worldwide, and our local gal is notorious for her extra-vivid red, orange, or yellow hourglass abdomen mark. The hourglass may serve to warn birds overhead against eating her, while hiding that same signal from any prey under the web. Clever girl.
And yes, she is a girl. At least, the widow that you’re likely picturing is one. Sexual dimorphism works overtime with these arachnids: the males are pale brown, striped, and usuallyhourglassless, with little beady eyes and scrawny legs. Males are half the the size or smaller of the dark, bulbous females. Their main objective in their short-lived and short-limbed lives is to breed before they die at around four months old.
She, on the other hand, can live over a year in the wild and much longer in captivity. She lays her first clutch of up to 300 eggs by the summer of her first birthday; the warmer months are spider breeding season. Typically, she breeds just once in her life, though she may produce more than 10 egg sacs from that mating. After a 14-30 day gestation, huge populations of widow spiderlings hatch. But due to their tendency to snack on each other, only around a dozen survive to adulthood.
You may have heard some ghoulish stories about the preferred post-coital snacks of female widows. The sexual cannibalism thing is mostly a myth. Our local lady widows only very occasionally eat suitors, and mainly when they’re hungry. The myth is not entirely without merit, though. Some species of widows, like the Australian redback, will throw themselves into the females’ jaws after mating; the pair may undergo this mate-and-snack cycle many times before the male finally dies. But that’s just not for our boys here at home.
If anything, the wee male widow is the more destructive one of the couple. Once he has been selected as a mate, he will begin disassembling her handiwork of a web into shreds. He then bunches these up with his own pheromones into a packet, before presenting some of his own silk in what researchers call a ‘bridal veil,’ before mating. This gift seems to keep other suitors at bay.
The male widow crashes with the female on her web as she rebuilds it and spins an egg sac. As a spinner, she is apparently an improviser, creating chaotic cobwebs rather than symmetrical webs like the classic “Charlotte’s Web”-style masterpieces of the California orbweaver. The widow sets up her messy web in an area with a lot of prey traffic to increase the chances of a meal while she waits for her young to hatch.
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Look past the messy strands. These webs, which serve as everything from nursery to dinner plate to speed-dating locale, truly are a feat. Like other spiders, she produces six different kinds of protein-rich silk for different purposes—cradling and encasing egg sacs, quick escape, defense, and even communication. The strongest type of silk is also the strongest known natural material: dragline, which acts as a quick escape rappel line for spiders as well as the structural basis of all webs.
Some black widow silk is twice as strong as orbweavers’ draglines, and researchers have tried to replicate it in a lab setting for textile use. During WWII, widow silk was likely used as the crosshairs for gun sights (I have so very many questions about the manufacturing process).
Peter J. Bryant
Let’s get to the neurotoxic elephant in the room: the venomous bites. Their reputation far exceeds the damage they actually cause. Black widow venom is primarily intended to paralyze prey, not defend against the giant, hostile spider-stompers that are humans. There have been no recorded U.S. deaths since 1983. We owe these excellent outcomes in part to the fact that Western black widow antivenom has been available in the U.S. since 1936.
Western black widows really do not want to bite you. In a study in which scientists repeatedly (and rudely, some might say) poked them with a fake finger, the majority did not bite on the first poke, and most of the spiders bit only when they were pinched on the body multiple times. Interestingly, some spiders opted to flick silk at the researchers instead, pulling out a strand from their spinnerettes to use as a defensive weapon of sorts. Many spiders opted for “dry bites” without any venom at all, even after multiple pinches. “The chances of getting bitten by a black widow are very low,” says Rodrigo Monjaras-Ruedaz, assistant entomology curator at the Natural History Museum of Los Angeles. Their fangs are very small, he notes, and they have a hard time breaking the skin of an adult person.
But in the very unlikely event of a bite, seek out medical help immediately. The antivenom works very well (see: zero fatalities in modern times) although there’s a low risk for allergic reaction. The venom affects the nervous system, and symptoms can include intense pain, muscle spasms, nausea and chills. Clean the bite site, keep it elevated and ice it, call Poison Control, and go to the ER if the pain continues. Don’t try to remove the venom. If this information hasn’t soothed your spider-bite fears, you can evict your widows by regularly sweeping out untouched corners.
At my North Bay home, I tried to (safely) search out my own black widows to observe them firsthand, for journalism. All I could find in storage sheds and cobwebby door frames were the deep-brown, originally European relatives of black widows—false widows (Steatoda grossa) and noble false widows (Steatoda nobilis), which were first seen in California in 2011. These two species have been observed more frequently in urban settings for quite a while now along with the also non-native brown widow (Latrodectus geometricus).
In a 2012 study in Los Angeles, brown widows far outnumbered the native black widows, especially among human dwellings and in urban areas. Monjaraz-Ruedas says,”We do not have enough data to fully understand how much these introduced species like, the brown widow are affecting black widows,” but there’s a definite trend. “In urban areas, people were very used to [seeing] the black widows,” he wrote in an email. “Suddenly, the brown widow was everywhere.” And now, the false widows seem to be overtaking the brown widows, he adds. “It is quite interesting that this transition happened more obviously in the cities, where [it] is easier for non-native species to establish,” he says. He’s using genomics to understand why such transitions are happening—whether, for instance, certain species are just better at dealing with climate change, or whether they’re outcompeting other spiders in their niches.
Climate change may also threaten black widows. There is evidence that intense heat encourages that aforementioned spiderling sibling cannibalism (as outlined in one of the best titles of scientific paper I’ve ever seen: Siblicide and the City). Spiders also tend to be more vulnerable to heat death than other critters,, since they can’t control their internal temperature like us sweaty mammals.
Black widow ecology is not a luxuriantly funded field of science, but there is some literature on the ecosystem benefits they provide. All spiders help cycle nutrients—eating, excreting, getting eaten, leaving their prey remnants around. In a study in Oklahoma, plants grew more robustly near black widow webs. They also kill pests like aphids, mosquitoes, and ticks. (Forget pricey fertilizer and pest controls, more black widows, please—they can double as Halloween decorations!) As with most native species that occupy an ecological niche, there are also likely benefits we don’t know about yet. Monjaraz-Ruedas urges us to “be gentle with them”—to relocate spiders instead of stomping them. “Spiders are also trying to adapt and survive to this changing world, the same way we do.”
