Crab spiders are arachnids found across diverse environments globally, from gardens and forests to mountains and grasslands. They belong to the Thomisidae family, with over 2,000 species identified worldwide. They employ unique hunting strategies and blend seamlessly into their surroundings.
Recognizing Crab Spiders
Crab spiders are identified by their distinctive crab-like appearance and movement. Their bodies are often flattened, round, or oval, typically 0.1 to 0.5 inches long, with females generally larger. A defining characteristic is their two front pairs of legs, noticeably longer and thicker than their rear legs, extending outwards like a crab’s claws. This unique leg structure enables them to scuttle sideways and backward.
Many species exhibit remarkable camouflage, with colors ranging from beige, brown, and black to bright white, yellow, green, or pink, often matching their habitat. Some, like the Goldenrod Crab Spider (Misumena vatia), can even change color over several days to weeks to blend with the flowers they inhabit. They are commonly found on flowers, leaves, bark, or in leaf litter, waiting for prey.
Understanding Their Potential Harm
Crab spiders are not considered dangerous to humans or pets. Their venom is effective on insects but not potent enough to harm larger animals or humans. Most species have mouthparts too small to pierce human skin.
Bites are rare and occur only if the spider feels provoked or threatened, as they are non-aggressive. If a bite occurs, symptoms are usually mild and localized, comparable to a bee sting. These may include minor pain, slight redness, and irritation or swelling at the bite site, which usually subside within a few hours. Crab spiders do not transmit diseases to humans.
Typical Crab Spider Habits
Crab spiders are ambush predators; they do not spin webs to catch food. They rely on camouflage and patience, remaining motionless on flowers or vegetation, waiting for insects. Their diet consists of various insects, including bees, flies, and butterflies. They capture prey much larger than themselves using potent venom.
Once prey is seized with their powerful front legs, the spider injects venom to paralyze it, then digestive enzymes to liquefy internal tissues for consumption. Crab spiders help control insect populations in ecosystems. While some species may occasionally consume nectar or pollen, their primary focus is insect prey.