Daddy-Long-Legs Spiders
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| Daddy long-legs spider | ||||||||||||
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 Cellar spider | ||||||||||||
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The Daddy long-legs spider, also called the Granddaddy long-legs spider, cellar spider, vibrating spider, or house spider, is a true spider and not a harvestman. Daddy longlegs is a name that is used for several unrelated arthropods with extremely long and thin legs, including these spiders, the harvestmen and tipulid crane flies. The Daddy long-legs spiders comprise the Pholcidae family, in the suborder Araneomorphae. The name "Daddy long-legs spider" has recently been accepted as the preferred common name for pholcids over "cellar spider".
Appearance
Pholcids are fragile spiders, the body being 2 to 10 mm in length and the legs are up to 30 mm long. Pholcus and Smeringopus have cylindrical abdomens and the eyes are arranged in two lateral groups of three and two smaller median contiguous (together) eyes. Spermaphora has a small globose (round) abdomen and its eyes are arranged in two groups of three and no median eyes. Pholcids are grey to brown with banding or chevron markings. Curiously, the shape of the Pholcus and Smeringopus's body reflects that of a peanut shell.
Habitat
These spiders are web weavers. The spider hangs inverted in a messy, irregular, tangled web. These webs are constructed in dark recesses, in caves, under rocks and loose bark, abandoned mammal burrows and undisturbed areas in buildings and cellars, hence the common name, "cellar spiders". The web has no adhesive properties but the irregular structure traps insects, making escape difficult. The spider quickly envelops its prey with silk and then inflicts the fatal bite. The prey may be eaten immediately or stored for later. When off their webs, pholcids walk with an unsteady, bobbing action.
When the spider is threatened by a touch to the web or when too large a prey hits the web, the spider becomes invisible by vibrating rapidly and becoming blurred, and for this reason have sometimes been called "vibrating spiders". Doing so might make it difficult for a predator to see exactly where the spider is, or may increase the chances of capturing insects that have just brushed their web and are still hovering nearby.
Certain species of these seemingly benign spiders invade webs of other spiders and eat the host, the eggs or the prey. In some cases the spider vibrates the web of other spiders, mimicking the prey to lure the host of the web closer.
Misconceptions
There is an urban legend stating that daddy long-legs spiders have extremely toxic venom, but their fangs cannot penetrate human skin. However there is no reliable research on the effects of pholcid venom in mammals, so any statement about their toxicity is just speculation. Additionally, pholcids do have a short fang structure (called uncate), but so do brown recluse spiders which can penetrate human skin and deliver potentially dangerous necrotoxin [1] (http://spiders.ucr.edu/daddylonglegs.html). In 2004 the Discovery Channel show MythBusters set out to test this myth (season 1, ep. 13 Buried in Concrete). One of the show's hosts was bitten, and the bite produced little more than a mild shortlived burning sensation.