“White spider” is a descriptive term referring to any spider exhibiting a white or predominantly white coloration, rather than a single specific species. Many different types of spiders can appear white due to various biological factors or environmental adaptations. This coloration can prompt questions about their identity and whether they pose any risk.
Commonly Encountered White Spiders
Among the spiders often observed with a white appearance, the goldenrod crab spider (Misumena vatia) is a prominent example. These spiders, found in gardens and meadows across North America, Europe, and Asia, are named for their crab-like posture and ability to move sideways. Females measure between 8 and 10 millimeters in body length, while males are considerably smaller. This species is an ambush predator, often found waiting on flowers to capture unsuspecting insects.
Another group that can appear white are sac spiders, such as Cheiracanthium inclusum. These spiders are generally pale yellow to greenish-yellow, which can look whitish. Females range from 5 to 9 millimeters in body length, with males being slightly smaller, though their leg span can reach up to 2.5 centimeters. Sac spiders are nocturnal hunters that do not build webs for prey capture, instead seeking shelter in silken sacs during the day in foliage, gardens, or human homes.
Jumping spiders, though often dark-bodied, can also display striking white markings. The bold jumper (Phidippus audax), for instance, is black but possesses a distinct white triangular spot on its abdomen, along with iridescent green mouthparts. These spiders are known for their excellent vision and active hunting style, relying on their sight to stalk prey rather than using webs.
Reasons for White Coloration
The white coloration in spiders primarily serves as a form of camouflage, allowing them to blend seamlessly into their environment. For instance, crab spiders like Misumena vatia can change their color between white and yellow over several days to match the flowers they inhabit, aiding both in ambush hunting and evading predators. This adaptation helps them remain undetected by both prey and larger animals that might pose a threat.
The white appearance often involves guanine, a metabolic byproduct. Spiders store guanine in specialized cells called guanocytes, located beneath their outer cuticle. These guanine crystals scatter and reflect light, creating a bright, matte white or silvery structural color, as opposed to a pigment-based color. This reflective quality contributes to their striking white hues. Additionally, genetic variations or recent molting can influence a spider’s coloration, sometimes resulting in a paler or whitish appearance.
Safety Concerns and Identification
Most white spiders encountered by humans are not considered dangerous. Their venom is mild and not potent enough to cause significant harm to people, and their fangs are too small to effectively penetrate human skin. Bites, if they occur, result in minor, localized symptoms such as pain, redness, or swelling, similar to a bee sting.
A spider’s color alone is not a reliable indicator of its danger level. No commonly encountered white spider in North America or Europe is considered medically significant.
For identification without direct contact, observing several characteristics can be helpful. Spiders, as arachnids, have eight legs and two main body segments: a cephalothorax and an abdomen. Noticing their general body shape, leg arrangement (e.g., crab-like or long and slender), and whether they build webs can provide clues. If unsure about a spider’s identity, it is always advisable to avoid handling it.