The Trachelas genus of spiders, commonly known as broad-faced sac spiders or broad-faced ghost spiders, are frequently encountered near human dwellings. These spiders are active, nocturnal hunters that do not build webs to capture prey, often bringing them into contact with people. While they are common household visitors, especially as temperatures drop in autumn, their presence is not a cause for significant alarm. Trachelas spiders are not considered medically significant to healthy humans, as their venom does not typically cause severe or life-threatening reactions.
Identifying Features of Trachelas Spiders
The Trachelas spider is generally small to medium in size. Adult females measure 7 to 10 millimeters in body length, while males are slightly smaller at 5 to 6 millimeters. A defining characteristic is the cephalothorax, the fused head and chest section, which is noticeably broad and often a dark, solid reddish-brown color. This darker cephalothorax contrasts with the abdomen, which is usually a duller pale yellow, tan, or light gray, sometimes featuring a faint dorsal stripe.
Their front pair of legs is typically thicker and darker than the three posterior pairs, providing a good identification clue. Trachelas are wanderers and nocturnal hunters, meaning they are not found in complex webs. During the day, they retreat into silken, sac-like shelters. These shelters are constructed in protected areas like under stones, loose bark, or in window sills and wall crevices.
Assessing the Danger: Toxicity and Venom
Trachelas spiders are venomous, meaning they inject toxins through a bite, but the toxicity level of their venom is considered mild. The venom is a neurotoxin secreted through the spider’s fangs, but it is not potent enough to cause serious harm to people. A bite is not classified as medically significant, contrasting with the potent venom of a Black Widow or Brown Recluse.
Although painful, the sensation is similar to a bee or wasp sting and does not indicate a systemic toxic reaction. The primary concern associated with a Trachelas bite is the possibility of a secondary infection, not the venom itself. It is theorized that bacteria on their fangs may be introduced during a bite, potentially leading to localized infection. However, this risk is low, and the initial reaction remains localized and minor for most individuals.
Bite Reaction and First Aid
A bite usually occurs as a defensive reaction when the spider is accidentally trapped against the skin. The immediate sensation is often described as a sharp, painful prick, similar to a bee sting. Common symptoms are minor and temporary, typically including painful redness and localized swelling around the bite site.
Managing a mild reaction begins with thoroughly cleaning the wound using mild soap and water to minimize infection risk. Applying a cool compress or an ice pack wrapped in a cloth for about 15 minutes each hour can help reduce pain and swelling. Over-the-counter pain relievers can be taken for discomfort, and an antihistamine may help if the area becomes itchy.
Applying an antibiotic ointment three times a day can help prevent secondary bacterial infection. Seek medical attention if the pain increases significantly, the swelling spreads, or if signs of a severe allergic reaction develop, such as difficulty breathing or hives. These severe symptoms are extremely rare but warrant immediate professional assessment.