Daddy long-legs spider

From Wikipedia, the free encyclopedia

iDaddy long-legs spider

Image:Pholcus.phalangioides.6908.jpg

Pholcus phalangioides

Scientific classification

Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Arachnida
Order:	Araneae
Suborder:	Araneomorphae
Superfamily:	Pholcoidea
Family:	Pholcidae C. L. Koch, 1851

Diversity

80 genera, 959 species

Image:Distribution.pholcidae.1.png

Genera

Holocnemus
Modisimus
Pholcus
Spermophora
many others

The Daddy long-legs spider, also called the Daddy long-legger, Granddaddy long-legs spider, cellar spider, vibrating spider, or house spider, is a true spider and is 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.

1 Appearance
2 Habitat
3 Diet
4 Systematics
5 Misconceptions
- 5.1 Most venomous?
- 5.2 Not Spiders?
6 Gallery
7 See also
8 External links

[edit] Appearance

Pholcids are fragile spiders, the body being 2 to 10 mm in length with legs which may be up to 50 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 gray to brown with banding or chevron markings. Curiously, the shape of the Pholcus and Smeringopus's body reflects that of a peanut shell.

[edit] Habitat

Pholcids are web-weaving spiders and are distributed worldwide. They hang inverted in messy, irregular, tangled webs. These webs are constructed in dark and damp 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 removed from their webs, pholcids are rather clumsy, and walk with an unsteady, bobbing action.

When the spider is threatened by a touch to the web or when too large a prey becomes entangled, the spider vibrates rapidly in a gyrating motion in its web and becomes blurred, almost invisible, and for this reason pholcids 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 (video of the "vibrating spider" vibrating). If the spider continues to be harassed it will retreat into a corner or drop from its web.

[edit] Diet

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 struggle of trapped prey to lure the host of the web closer. Pholcids are natural predators of the Tegenaria species, and are known to attack and eat Redback spiders and Huntsman spiders. [1] [2] It is this competition that helps keep Tegenaria populations in check, which may be advantageous to humans who live in regions with dense hobo spider populations.

[edit] Systematics

For a complete list of the genera and species in this family, see List of Pholcidae species.

[edit] Misconceptions

[edit] Most venomous?

There is an urban legend stating that Daddy long-legs spiders have the most potent venom of any spider, but that their chelicera (fangs) are either too small or too weak to puncture human skin; the same legend is also repeated of the harvestman and crane fly, also called "Daddy Longlegs" in some locales. Indeed, pholcid spiders do have a short fang structure (called uncate). However, brown recluse spiders also have uncate fang structure, but are able to deliver potentially fatal bites. Either pholcid venom is not toxic to humans or there is a musculature difference between the two arachnids, with recluses, being hunting spiders, possessing stronger muscles for fang penetration.

Pholcid venom has never been scientifically tested on mammals. This would normally require milking the spiders and injecting the venom into humans or mice. In any case, there are no known cases of a pholcid spider ever biting a human and causing any serious effects.

In 2004 the Discovery Channel show MythBusters set out to test the daddy long-legs myth (season 1, episode 13 "Buried in Concrete"). After measuring the spider's fangs at approximately 0.25 mm (average human skin thickness is about 0.10 mm) the show's host was apparently bitten, although the bite produced little more than a mild short-lived burning sensation. This appears to confirm the suspicion that pholcids can penetrate human skin, but that their venom is practically harmless to humans. Additionally, recent research has shown that pholcid venom is actually relatively weak in its effects on insects as well. [3]

[edit] Not Spiders?

Another misconception is that the Daddy long-legs spider is not a true spider. This misconception arises from the multiple uses of the name Daddy long-legs. It is the Harvestman (which is also called Daddy long-legs) which is an arachnid but not a true spider. The Daddy long-legs spider is a true spider.