Meet The Itsy Bitsy Black Widow’s Cousin

“Consider the black widow spider. It’s a timid little beastie, useful and, for my taste, the prettiest of the arachnids, with its shiny, patent-leather finish and its red hourglass trademark. But the poor thing has the fatal misfortune of possessing enormously too much power for its size. So everybody kills it on sight.”

― Robert A. Heinlein, Stranger in a Strange Land


If you live in the United States you are most likely familiar with the black widow spider (Latrodectus mactans, Latrodectus hesperus, Latrodectus variolus). Known for its venomous bite, cannibalistic mating habits, and the distinctive red pattern on its abdomen, the black widow is probably the most feared spider in the United States.  Black widow venom contains a potent neurotoxin that can cause localized burning pain, sweating, muscle pain and weakness, headache, nausea and vomiting, tremors, difficulty breathing, partial paralysis, and very rarely, death.  Systemic responses are most common in the very young or old.  Severity of the reaction is dose dependent and the bite victim usually recovers in 1 to 5 days. Luckily, black widow bites are not very common because black widows prefer to shy away from human activity, living in protected areas, under debris, and areas of high insect activity. Unfortunately, the black widows “new” cousin, the brown widow, is a little more easily found.

The brown widow spider (Latrodectus geometricus) was  first documented in the United States in 1935, in Florida. Originally believed to be from Africa, brown widow populations are now established in the southeastern United States, from Texas to South Carolina, and in Southern California. The brown widow is now a “common” sight in areas with established populations.

 The University of California-Riverside recently published a study in the July issue of the Journal of Medical Entomology comparing the habitats of the two species. The study found brown widows around urban structures, such as the outside of homes, in parks, on playground equipment, and landscaping areas. Brown widow spiders were rarely found in agricultural settings and natural habitats. On the other hand black widows can be found in natural habitats and though there is overlap in habitat, black widows are much less common (20 times less) and prefer to be less exposed. Brown widows require minimal protection and were regularly found under outdoor furniture and under the recessed handles of trash bins.

The good news is, neither species were found in indoor living spaces, and though brown widow spiders are more common, their venom is much less dangerous than the venom of the black widow. Spider bites are extremely uncommon, according to the study. Despite large spider populations there has only been only one identified brown widow envenomation in South California, and the symptoms were minor. Though bite risk is low, one should still be careful when reaching into “spider-friendly” nooks and crannies.

The authors of the study were unsure whether brown widows are displacing black widows. Though displacement of the black widow may be a good thing for humans because of the reduced risk of severe envenomation, we do not yet know the potential ecological effects of such a possible species switch. Spiders are important members of the ecosystem because they serve as natural pest control and shouldn’t be taken for granted.

On another note, if you find spiders completely fascinating like me, the American Museum of Natural History in New York City will be opening a new exhibit named “Spiders Alive!” starting July 28. The exhibit will include both live and preserved specimens, along models, videos, and  live  demonstrations. The exhibit is appropriate for spider fans of all ages.


Black Widow via Shutterstock

by Maddie Perlman-Gabel

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