Spiders often evoke a mix of fear and fascination. Running crab spiders, with their distinctive appearance and swift movements, frequently spark curiosity. Understanding these spiders involves recognizing their physical traits, clarifying their venom status, and knowing what to expect if a bite occurs.
Identifying Running Crab Spiders
Running crab spiders (family Philodromidae) have unique characteristics. Their bodies are typically flattened and elongated, allowing them to navigate tight spaces and blend into their surroundings. They are known for their crab-like appearance and ability to move rapidly, often sideways or backward, which gives them their common name. The front two pairs of legs are longer and more robust, often held outstretched like crab claws.
Their coloration frequently matches their habitat, ranging from tan, brown, or gray to brighter yellows and greens, providing effective camouflage. Unlike many spiders, running crab spiders do not build webs to catch prey. Instead, they are active hunters, relying on speed and agility to ambush insects and other small arthropods. They can be found in various environments, including gardens, prairies, forests, and sometimes near human dwellings.
Are Running Crab Spiders Venomous?
A common confusion is whether spiders are “poisonous” or “venomous.” “Poisonous” refers to ingested toxins, while “venomous” describes toxins injected, typically through a bite. Nearly all spiders produce venom, making them venomous. For humans, the key distinction is whether that venom is medically significant.
Running crab spiders are venomous, but their venom is primarily adapted for subduing insect prey. The compounds are effective against small invertebrates, quickly immobilizing prey like flies and bees. Therefore, while they possess venom, it poses little to no threat to human health.
What Happens After a Running Crab Spider Bite?
Bites from running crab spiders are rare, as these spiders are not aggressive and prefer to retreat when disturbed. If a bite occurs, it is usually accidental, such as when the spider becomes trapped against the skin. Effects on humans are typically mild and localized.
The sensation is often described as similar to a minor bee sting or mosquito bite, causing temporary, localized pain, slight redness, or mild swelling at the bite site. These symptoms usually subside within a few hours. Severe reactions are uncommon and typically due to an individual’s rare allergic sensitivity, not the venom’s potency. Basic first aid includes cleaning the area with mild soap and water and applying a cool compress. Medical attention is generally not required unless symptoms worsen significantly or signs of infection or a severe allergic reaction, such as difficulty breathing, develop.