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This story originally appeared on WIRED en Español and has been translated from Spanish.
Summer arrives, and with it comes an arachnophobic furor—frantic reports about the intrusion of recluse spiders into our homes. Also known as fiddlebacks or violin spiders, these are arachnids of the genus Loxosceles. They’re found in warm areas across the world, including many parts of the USA, and particularly in Mexico, which has the greatest diversity of recluse spiders in the world, with 40 different species.
Headlines declare that the start of May is “recluse spider season,” and that people need to watch out. It’s true that in their fangs these spiders carry a potent venom, which under certain circumstances can be lethal, but really they are elusive creatures that almost always seek to remain unnoticed. We should not get carried away with anti-fiddleback hysteria, much less replicate it. Such anxiety is unscientific, says Diego Barrales Alcalá, the creator of the arachnid identification platform @Arachno_Cosas. The idea of a supposed season of recluse spiders, promulgated by the media, lacks evidence.
“Fiddlers have become the favorite villain and, unfortunately, according to what I have seen, the problem is cyclical. Every so often the ‘season’ arrives. But not of fiddlers, but of fake news,” Barrales Alcalá says. The activity of these arachnids doesn’t vary according to the time of the year, he says. And in his native Mexico, what limited statistics there are on bites certainly don’t add up to the concern seen in the media.
While recluse spiders choose to inhabit our homes, they are not aggressive. Usually they live away from people, in cellars and uncrowded areas of the house. Bites, when they do happen, occur typically when there’s unintentional contact between humans and spiders or due to people deliberately trying to manipulate them.
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If a bite does happen, humans have to contend with a necrotic venom that inflames tissues and which can cause gangrene. In some cases, a purplish-blue sore forms on the skin. In a fraction of cases, estimated to be between 10 and 16 percent according to the most recent data from the Mexican Ministry of Health, the effects of the venom can also become systemic (leading to what’s known as “systemic loxoscelism”). In such circumstances, if not properly treated, a bite can become lethal.
The ministry states that there’s no reliable data on how frequently systemic loxoscelism occurs, but it notes that on average, it sees only about 100 cases per year throughout the country.
Complicating matters is the fact that a recluse spider bite is not usually painful, and so often goes unnoticed, at least initially. There are also several conditions that can be misdiagnosed as loxoscelism, ranging from other insect bites to herpes. This makes it difficult to make correct treatment decisions without toxicological testing. An immunological test that can determine whether something is a Loxosceles bite exists, as does an antivenom. These are useful, if available.
In Need of Positive Spin
These spiders face a very serious problem of social disapproval, largely fed by the media. “The media play an important role in the construction and circulation of the perception of risk associated with animals,” states a research paper published in the journal Current Biology in 2022. “Very feared groups, such as spiders, usually end up in the center of attention on social networks and traditional media.” As detailed in the illustration below, the paper found that Mexico’s spider reporting was particularly sensationalist.
This isn’t to downplay the severity of a possible bite. But the reality is that bites aren’t something that happen every day, whereas in the face of the ongoing biodiversity crisis, combating misinformed arachnophobia is becoming more and more urgent. The future of ecology, at least as we know it, depends largely on arachnids, insects, and other invertebrates being protected.
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Spiders are also important allies in our homes, keeping at bay various organisms that can become pests, such as flies, codling moths, and mosquitoes, some of which may be vectors of disease. These spiders also keep away other unwanted species such as scorpions and bedbugs. But because of concerns around recluse spiders, many arachnids are killed that turn out to be species that present no risk at all. In Mexico City alone, it is estimated that between 80 and 90 species of spider are frequently found in homes.
Barrales Alcalá recalls a particularly bad episode of media sensationalism from the years prior to the pandemic, when it was said that fiddlebacks were “invading” Mexico City. In reality, a recluse spider species, Loxosceles tenochtitlan, had always been endemic to the Valley of Mexico—the issue was that it had only been described for the first time in 2019, and so was getting attention. “In any case, the ones who invaded their natural space are us, human beings,” said Alejandro Valdez Mondragón, leader of the research group behind the “discovery,” in an interview for National Geographic at the time.
For Barrales Alcalá, the issue is that we’re being pushed to notice these spiders only now—and notice them in a negative way. “Maybe, after seeing in the media the campaigns that warn about the season, after hearing over and over again, ‘Here comes the bogeyman,’ we turn to see the spider that is there, in the corner, and realize: ‘Oh boy, it’s a violinist!’” he says. “That doesn’t mean we didn’t have it there before.”
