The Brazilian wandering spider, belonging to the genus Phoneutria, has gained a reputation for its potent venom and aggressive defensive displays. While often sensationalized in media, understanding the characteristics and behaviors of these spiders can help to demystify their notoriety and provide clarity on the actual risks they pose. This article aims to offer a factual overview of the Brazilian wandering spider, from identification to prevention.
Identifying the Brazilian Wandering Spider
Brazilian wandering spiders are large arachnids, with a leg span that can extend up to 18 centimeters (7 inches). They generally have hairy bodies that range in color from brown to gray, and some species exhibit light-colored spots on their abdomen. A distinguishing feature for many species is the presence of black and yellow or white bands on the underside of their two front legs.
These spiders are known for their characteristic defensive posture, in which they lift their front two pairs of legs high into the air, revealing these banded undersides, and sway from side to side. This display indicates the spider feels threatened and is prepared to bite. Unlike many other spiders, Brazilian wandering spiders do not build webs to catch prey; instead, they are nocturnal hunters that wander the forest floor at night in search of insects, small amphibians, reptiles, and even mice. During the day, they seek shelter in dark, moist places, such as under logs, in crevices, or within banana plants, which has earned them the nickname “banana spiders”. This preference for hidden spaces can occasionally lead them into human dwellings, where they might hide in shoes, clothing, or other stored items.
Understanding the Danger
The Brazilian wandering spider’s venom is considered highly potent and is primarily neurotoxic, meaning it affects the nervous system. This venom contains a complex mixture of peptides and proteins that interact with ion channels and chemical receptors in the neuromuscular system. When a human is bitten, symptoms can appear rapidly, often within 10 to 30 minutes, and can be quite severe.
Initial symptoms commonly include intense burning pain at the bite site, sweating, and goosebumps. As the venom spreads, systemic effects can manifest, such as high or low blood pressure, irregular heart rate, nausea, abdominal cramping, vertigo, and blurred vision. A notable, though less common, symptom in males is priapism, a prolonged and painful erection, which has even led to studies exploring the venom’s components for medical applications in erectile dysfunction. While the bites can be serious and cause significant discomfort, fatalities are rare, especially with prompt medical attention, with only a small number of deaths globally attributed to Phoneutria.
What to Do if Encountered
If you encounter a Brazilian wandering spider, the most important action is to remain calm and avoid provoking it. These spiders typically only bite when they feel threatened or are accidentally disturbed. If possible, slowly back away from the spider to create distance.
Should a bite occur, seeking immediate medical attention is essential. Contact emergency services or go to the nearest hospital without delay. While waiting for medical help, some first aid measures can be taken: clean the bite site thoroughly with soap and water, and apply a cold compress or ice pack to the area to help reduce swelling and pain. It is advisable to keep the bitten limb still and elevated, as this may help slow the spread of venom. Do not attempt to catch or handle the spider if it puts you at further risk, and avoid applying tourniquets or trying to cut the wound, as these actions can worsen the situation. Medical professionals can assess the severity of the envenomation and administer antivenom if necessary, which is the most effective treatment.
Preventing Encounters
Minimizing encounters with Brazilian wandering spiders, particularly in areas where they are common, involves adopting specific precautions around the home and outdoors. Since these spiders are nocturnal and seek dark, secluded places during the day, it is helpful to keep living spaces tidy and clutter-free. Organizing storage areas like garages, attics, and basements can reduce potential hiding spots.
Before putting on shoes or clothing, especially items left on the floor or stored in dark areas, it is advisable to shake them out to dislodge any hidden spiders. When handling items stored in undisturbed spaces, such as woodpiles, sheds, or outdoor furniture, wearing protective gloves and sturdy footwear can provide an added layer of safety. Sealing cracks and openings in walls, windows, and doors can also help prevent spiders from entering your home. Additionally, if living in or visiting regions where these spiders are prevalent, being mindful of surroundings, especially when reaching into dark areas or handling vegetation, can help avoid accidental disturbances.