Brown Widow

Latrodectus geometricus — the brown widow — is one of about 30 species in genus Latrodectus, the true widows. Native to South Africa (most likely origin) and South America, the brown widow is highly cosmopolitan and now invasive across most warm-climate regions of the world. The species was first detected in Florida in the early 1900s as occasional records and exploded in abundance across the southern US starting in the early 2000s, displacing the native southern black widow (L. mactans) from urban and suburban habitat: garages, sheds, outdoor furniture, mailboxes, irrigation boxes. The species is identified by mottled brown-and-tan coloration, an orange-red hourglass on the underside of the abdomen (the black widow has a brilliant red hourglass, the brown widow's is muted orange), and the distinctive 'spiky' egg sacs (covered in pointed silken protuberances, in contrast to the smooth round egg sacs of black widow). Brown widow venom is, drop-for-drop, more toxic than black widow venom (in mouse-LD50 studies), but the brown widow injects substantially less venom in a defensive bite, so medical outcomes are typically milder than black widow envenomations. Brown widow bites cause local pain, sweating, nausea, and muscle cramping; severe systemic envenomation (latrodectism) is rare. The species is non-aggressive but bites readily when contact is made, especially when the spider is brushed against or grabbed.