Pholcidae, or daddy long legs, are members of the arachnid family that includes spiders. The term "daddy long legs" has also been mistakenly used for harvestmen, which are arachnids, but not spiders, and crane flies, which are insects. They are found globally apart from the Arctic and Antarctic. There is a myth surrounding daddy long legs that they have the most potent venom of any arachnid, but they cannot penetrate human skin. This is untrue, but to other insects, proper daddy long legs are very dangerous.
Daddy long legs, as opposed to harvestmen and crane flies, eat other insects. This includes anything it can get its hands on. Daddy long legs are both scavengers and predators, depending on what they are catching.
True daddy long legs, like spiders, spin webs. Unlike spiders, however, a daddy long legs web is not sticky -- it is an irregular shape, which make it harder for insects to escape. Once it has trapped an insect in its web, the daddy long legs wraps it in silk, injects venom by biting it and waits for it to decompose before eating it in a similar way as a spider.
Some species of daddy long legs invade the webs of other spiders. They will eat prey caught in the web and then mimic the vibrations. The web's host will come to investigate and be bitten by the daddy long legs, who will then eat that spider as well.
The myth surrounding daddy long legs originates from the fact that it can kill much more venomous spiders, like the redback and huntsman. Modern studies suggest this has little to do with venom potency; rather, it is because daddy long legs are faster than other spiders as they have smaller bodies and longer legs.
Harvestmen, which are often mistaken for daddy long legs, survive mainly on vegetation as they have no way of catching prey. Decaying plants are a staple food, along with insects they find caught in other traps.