The cellar spider, scientifically classified in the family Pholcidae, is a common household presence often recognized by its long, fragile appearance. This species is widely known by the common name “daddy long-legs spider,” a designation that often causes confusion with other arachnids and insects. The spider’s reputation for being large is almost entirely due to its disproportionately long legs, which create a misleading impression of its true body size.
Clarifying Identification
The name “cellar spider” most commonly refers to the species Pholcus phalangioides, a long-bodied member of the Pholcidae family. These spiders are cosmopolitan, found all over the world, particularly in human structures like basements and cellars. The descriptive name is sometimes incorrectly applied to other spiders, or even to the Harvestman (Opiliones), which is a different order of arachnid altogether. This article focuses specifically on the dimensions of the true cellar spider, P. phalangioides, characterized by its slender body and exceedingly fine legs.
Specific Body Dimensions
When measuring the actual body of the Pholcus phalangioides, which includes the cephalothorax and the abdomen, the size is quite small. The body length typically ranges between 6 and 10 millimeters, or roughly a quarter to a third of an inch. Female cellar spiders are generally slightly larger than males, often measuring around 7 to 8 millimeters in length. Males tend to be slightly smaller, averaging around 6 millimeters. The body itself is pale, often translucent, and slender, which emphasizes the length of its appendages.
The body’s small size is often obscured by the spider’s characteristic posture when resting in its web. The spider’s form is often described as resembling a peanut or a skull due to the shape of the cephalothorax. The core body is physically insignificant compared to many other spiders, making the creature appear delicate. This small, lightweight core allows the spider to support such long, thin legs without difficulty.
The Impressive Leg Span
The reason cellar spiders appear so large is due to the enormous span created by their eight legs, which can be five to six times the length of their body. The average length of a single leg on an adult female can be around 50 millimeters, or nearly two inches. When measured tip-to-tip across the widest point, the total leg span of P. phalangioides can reach up to 50 to 70 millimeters, which is about two to three inches.
This extensive reach gives the cellar spider its intimidating reputation, despite its harmless nature. The legs are extremely thin and delicate, covered in fine, gray bristles that add to their wispy appearance. Their extreme length relative to the body is a major factor in the spider’s successful web-building and hunting strategy.