False widow spiders are gaining attention, often due to their resemblance to more notorious species. Belonging to the genus Steatoda, these spiders are now more prevalent in many regions. Understanding their physical traits, preferred environments, and venom provides clarity regarding their presence.
Identifying the False Widow
Identifying false widow spiders, particularly the noble false widow (Steatoda nobilis), involves observing several physical characteristics. Female noble false widows measure between 9.5 and 14 millimeters in body length, with males being slightly smaller, around 7 to 10 millimeters. Their bodies are dark brown to black and possess a glossy, rounded abdomen. A distinguishing feature on the abdomen is often a pale pattern, sometimes described as skull-shaped, though this marking can vary or be absent. The legs are usually a reddish-brown color.
False widows exhibit a narrow white or lighter band at the front of their abdomen, near the head. Their webs are characteristically tangled and irregular, forming a criss-cross scaffold of threads rather than organized wheel-shaped webs. While the noble false widow is the largest and most commonly reported, other species like the cupboard spider (Steatoda grossa) and the rabbit hutch spider (Steatoda bipunctata) are also found, with varying sizes and markings.
Where False Widows Live
False widow spiders are adaptable, found in various environments, often near human activity. Originally from Madeira and the Canary Islands, the noble false widow (Steatoda nobilis) has spread globally, establishing populations in Western Europe, North and South America, and other regions, partly due to human movement and global trade. They prefer sheltered, undisturbed locations.
Indoors, these spiders commonly inhabit attics, sheds, garages, and wall crevices, seeking dark, secluded corners. Outdoors, they can be found under stones, logs, tree bark, and within garden structures. Their tangled webs are often suspended at least 1.5 meters off the ground, allowing them to capture flying insects. While present year-round, their presence indoors may become more noticeable as the weather cools in autumn.
Understanding Their Venom and Bite
False widow spiders are venomous, but their bites are generally mild to moderate, often compared to a bee or wasp sting. The venom is neurotoxic, similar to black widow venom, but significantly less potent. Most bites occur when the spider feels threatened, such as when accidentally trapped against skin or handled. False widows are not aggressive and prefer to flee.
Common symptoms of a false widow bite include localized pain, which may radiate from the bite site, along with swelling and redness. Some individuals may experience itching, tingling, or numbness in the affected area. Less common, more systemic reactions can include nausea, headache, general malaise, or feverishness, a set of symptoms known as steatodism. While uncomfortable, severe reactions requiring hospitalization are infrequent, and fatalities from false widow bites have not been reported. Severe outcomes, such as skin breakdown or infection, are typically due to secondary bacterial infection rather than the venom.
False Widows vs. Black Widows
Distinguishing false widows from black widows is important due to the latter’s more potent venom. True black widows (Latrodectus species) are glossy jet-black with a prominent red or orange hourglass-shaped marking on the underside of their abdomen. False widows, in contrast, are brown or purplish-brown and lack this distinct hourglass symbol, instead often displaying varied pale markings on their globular abdomen. While both have rounded body shapes, adult female black widows tend to be larger than false widows.
Web structures also differ; black widows spin irregularly shaped, sticky webs, similar to false widows, but are often observed hanging upside down in their webs. The severity of their bites is a major distinction. Black widow venom is considerably more potent, capable of causing more severe symptoms and requiring immediate medical attention. False widow bites, as noted, result in symptoms comparable to a wasp sting, with severe reactions being uncommon.
Coexisting with False Widows
Managing false widow spiders around the home involves practical steps to minimize encounters. Reducing clutter in sheds, garages, and attics can limit their preferred sheltered habitats. Sealing cracks and crevices around windows and doors can also help prevent them from entering living spaces. While these spiders can be found indoors year-round, they may be more noticeable during cooler months as they seek warmer environments.
If a false widow spider is found inside, safe removal methods, such as using a glass and card to catch and release it outdoors, are recommended. False widows are not aggressive; bites usually only occur when accidentally trapped or provoked. Should a bite occur, cleaning the area with soap and water and applying a cool compress can help alleviate symptoms. Medical attention is advisable if symptoms worsen, if there are signs of infection, or if severe reactions like difficulty breathing, nausea, or dizziness develop.