Pholcidae

Lore & Background

Pholcidae hang inverted in messy, irregular-shaped webs constructed in dark and damp places such as caves, under rocks, loose bark, abandoned mammal burrows, and in human buildings like attics and cellars. Their webs have no adhesive properties and rely on irregular structure to trap prey. When prey is detected, the spider quickly envelops it with silk-like material, eating it immediately or storing it for later, then cleaning the web by dropping the carcass. Some species exhibit a threat response when disturbed: they vibrate rapidly in a gyrating motion, sometimes falling into a circular rhythm. This may make it difficult for a predator to locate or strike the spider, signal a rival to leave, or further entangle prey. If disturbed further, the spider retreats or drops from its web. Pholcids prey on insects and also invade webs of other spiders to eat the host, eggs, or prey. They are known to attack and eat redback spiders, huntsman spiders, house spiders, and Tegenaria funnel weaver spiders. They may be beneficial in regions with dense hobo spider populations by keeping Tegenaria in check.

Reader's Guide

The Pholcidae family is significant for its widespread distribution, unique web structure, and the persistent urban legend that daddy long-legs spiders have the most potent venom but cannot bite humans. The source article clarifies that this is not true: pholcid venom is not medically significant, and while they can bite humans, their bites cause only mild, short-lived effects. The legend may arise from the fact that pholcids prey on deadly venomous spiders like redbacks, leading to the mistaken belief that they must be more venomous. In reality, they incapacitate prey from a safe distance using silk. The family's threat response—rapid vibration—has earned them the name 'vibrating spiders' and is a notable behavioral adaptation. Pholcids are also distinguished from harvestmen (Opiliones) by having two body segments and eight eyes (or six in some genera), while harvestmen have one pair of eyes and a single-segment body.

Did You Know?

• Pholcidae have two groups of three eyes each, with a possible pair of small eyes in between, for a total of six or eight eyes.
• The common name 'daddy long-legs' is also used for harvestmen and crane flies, which are not spiders.
• Pholcids prey on redback spiders, huntsman spiders, and house spiders, and may help control hobo spider populations.