Green-colored spiders are common worldwide, representing various species. The green hue serves a biological function, allowing these arachnids to blend seamlessly into foliage and ambush prey. While they share this striking feature, these spiders belong to distinct families, each with unique characteristics and habits. This natural camouflage often prompts questions about their safety and identification.
Identifying Common Green Spiders
The bright green spiders encountered most often in North America and Europe typically fall into three main groups, each distinguishable by body shape and behavior. Green Lynx Spiders (Peucetia viridans) are large, active hunters, with females growing up to three-quarters of an inch in body length, not including their long, spiny legs. These spiders are not web-builders; they are ambush predators found primarily on shrubby vegetation, tall grasses, and wildflowers, using their bright color for camouflage. A distinctive feature is the prominent black spines covering their long, slender, pale green legs, along with a hexagonal eye arrangement on the cephalothorax.
Green Crab Spiders (family Thomisidae) are named for their crab-like appearance, which includes a wide, flattened body and the ability to move sideways and backward. Species like the American Green Crab Spider (Misumessus oblongus) are typically smaller than the Lynx Spider, often measuring less than a quarter of an inch. They are frequently seen waiting motionless on flowers, where their coloration provides camouflage as they ambush flying insects like bees and flies. Some crab spiders possess the remarkable ability to slowly change color between white, yellow, or green to match the flower they are hunting on, a process that can take several days.
Another group, the Sac Spiders (genus Cheiracanthium), sometimes exhibit a pale green or yellowish-green hue, though they are often referred to as “yellow sac spiders”. These spiders are smaller, usually between one-quarter and three-eighths of an inch, and have a somewhat translucent body with long, slender legs. Unlike the other two groups, sac spiders are nocturnal hunters and do not build webs for catching prey, instead constructing a small, silk tube or sac-like retreat in high corners, under leaves, or at wall-to-ceiling junctions where they rest during the day.
The Science Behind Their Green Color
The green coloration in these spiders is a result of camouflage in their plant-based environments. This color is achieved not through pigments found in plants, but through specialized chemical compounds within the spider’s own body. The most common mechanism involves bile pigments, specifically a class known as bilins.
In many true green species, such as the Green Huntsman Spider (Micrommata virescens), the green color results from biliverdin or a related bilin pigment like micromatabilin, which is deposited in the hemolymph (the spider’s blood) and interstitial tissues. Biliverdin is a tetrapyrrolic compound formed from the breakdown of heme, a component of hemoglobin, and is the same pigment responsible for the green color seen in healing bruises in humans. The final hue can be affected by how the pigment is combined with other chemicals or proteins in the body.
While pigmentary color is most frequent, some spiders also achieve green coloration through structural means or a combination of pigments. Structural color arises from the way light interacts with microscopic physical structures on the spider’s cuticle or hairs, causing light to be scattered or interfered with. For example, a bright green appearance can sometimes be produced by a combination of pigmentary yellow and structural blue, as the two colors mix when reflected back to the eye.
Assessing the Danger of Green Spiders
Despite their striking appearance and ability to ambush prey, the green spiders commonly found in homes and gardens pose virtually no medical threat to humans. The general rule is that the venom of both Green Lynx Spiders and Green Crab Spiders is designed to quickly subdue small insects, and it is not medically significant to people. Bites from these species are extremely rare, typically occurring only if the spider is accidentally trapped against the skin or if a female is aggressively guarding an egg sac.
If a bite were to occur, the symptoms are generally mild, often involving only localized pain, redness, and minor swelling, comparable to a mosquito bite or a bee sting. The effects are usually short-lived and resolve within a few hours or a day. Green Lynx Spiders have a unique defensive mechanism where they can spray venom, which has been reported to cause temporary eye irritation if it makes contact.
Sac Spiders, which may have a greenish tint, are occasionally reported to have a more painful bite than the other two species, though their venom is still not considered medically significant for the average person. Any bite should be cleaned with soap and water, and a cold compress can be applied to reduce swelling. An individual should seek medical attention only if they experience signs of a severe allergic reaction or if the bite area shows signs of infection or unusual complications.