Approximately 15% of black widow bites are 'dry bites,' in which envenomation does not occur, and 85% of bites involve some degree of envenomation. Patients who are bitten by a black widow spider may develop clinical signs within 8 hours. The clinical signs of a spider bite vary with which species delivered the bite. What are the clinical signs of a spider bite? These spiders are reclusive and not aggressive, but can bite when they feel cornered or trapped (if accidentally laid on, or trapped between an animal and its bedding). Brown recluse spiders are yellow-brown in color, with a violin-shaped marking on their back. Female brown recluse spiders are larger and more venomous than males. There are six Loxosceles species in the United States, with the most notable being the brown recluse spider ( Loxosceles reclusa). Recluse spiders are found worldwide, in dark, warm places. Immature female black widows lack this coloration, being red, brown, or beige in color, however, they are also capable of producing envenomation. Female black widows are significantly larger and more venomous than males they are dark grey to black, with a red or orange hourglass marking on their round abdomen. There are five Latrodectus species found within the United States and the most common of these is the black widow spider ( Latrodectus mactans). Widow spiders are found in tropical and temperate areas worldwide. The two groups of spiders responsible for most medically-significant spider bites include the widow spiders ( Latrodectus spp., including the black widow spider) and the recluse spiders ( Loxosceles spp., including the brown recluse). Most spiders are unable to produce medically-significant envenomations (the process by which venom is injected into an animal) however, because their small mouthparts are unable to penetrate the skin. There are over 30,000 species of spiders worldwide, and most of these spiders are venomous. Which spiders are associated with problematic spider bites?

Spider bits