Pholcus phalangioides, commonly known as the cellar spider or daddy long-legs spider, is a widespread arachnid found globally. These spiders are frequently encountered in homes, basements, and other sheltered indoor environments. This article explores their characteristics, habits, and addresses a common misconception about their venom.
Identifying the Cellar Spider
Cellar spiders have distinct physical features that aid in their identification. Their bodies are small and slender, typically ranging from light brown to grayish or translucent in color. They are characterized by exceptionally long, thin legs, which can be five to six times the length of their body, averaging around 50 mm for adult females. The cephalothorax, the fused head and thorax, sometimes displays a pattern resembling a skull, leading to the nickname “skull spider”.
It is important to distinguish Pholcus phalangioides from other creatures also referred to as “daddy long-legs.” Harvestmen, or Opiliones, are arachnids but are not true spiders, possessing a single body segment and lacking silk glands or venom. Crane flies, on the other hand, are insects with wings and no fangs or venom. Unlike these, the cellar spider is a true spider with a two-part body and the ability to spin webs.
Habitat and Behavior
Cellar spiders prefer dark, quiet, and humid environments, such as cellars, basements, garages, and room corners. Their webs are typically messy, irregular tangles of silk, unlike the structured orb webs of many other spider species. These spiders often hang upside down within their webs.
They are carnivorous, feeding on insects and other small invertebrates. Cellar spiders hunt and consume other spiders, including dangerous species like black widows and redback spiders. They achieve this by rapidly wrapping prey in silk from a safe distance using their long legs, before administering a venomous bite. When threatened, Pholcus phalangioides exhibits a defensive behavior called “whirling,” rapidly vibrating its body in a circular motion on its web, making targeting difficult for predators.
Debunking the Venom Myth
A common urban legend claims cellar spiders have highly potent venom but cannot bite humans due to small fangs. This myth is not supported by scientific evidence. Research indicates that Pholcus phalangioides venom is not potent to humans or even to insects.
While their fangs are relatively small, they can pierce human skin. However, any bite from a cellar spider is medically insignificant, causing only a mild, short-lived stinging sensation, if felt. The myth likely originated from observations of cellar spiders preying on more venomous spiders.