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===Gait===
===Gait===
''Pholcus phalangioides'' often uses an alternating tetrapod gait (first right leg, then second left leg, then third right leg, etc.), which is commonly found in many spider species. However, frequent variations from this pattern have been documented during observations of the spiders’ movements.
''Pholcus phalangioides'' often uses an alternating tetrapod gait (first right leg, then second left leg, then third right leg, etc.), which is commonly found in many spider species. However, frequent variations from this pattern have been documented during observations of the spiders’ movements.

===Group Behavior===
The grand-daddy longlegs has been observed in the wild to occasionally congregate en masse, particularly during the evenings when the weather is mild. This gathering, technically known as a "jamboree," allows the grand-daddy longlegs to enjoy banjo music, dancing, and social networking amongst its neighbors and kinfolk.


==Systematics==
==Systematics==

Revision as of 00:46, 17 March 2011

Pholcidae
Pholcus phalangioides
Scientific classification
Kingdom:
Animalia
Phylum:
Arthropoda
Class:
Arachnida
Order:
Araneae
Suborder:
Araneomorphae
Superfamily:
Pholcoidea
Family:
Pholcidae

Genera

Holocnemus
Modisimus
Pholcus
Physocyclus
Psilochorus
Smeringopus
Spermophora
 many others

Diversity
80 genera, c. 1000 species

Pholcidae are a spider family in the suborder Araneomorphae.

Some species, especially Pholcus phalangioides, are commonly called granddaddy long-legs spider, daddy long-legs spider, daddy long-legger, cellar spider, vibrating spider, or house spider. Confusion often arises because the name "daddy long-legs" is also applied to two distantly related arthropod groups: the harvestmen (which are arachnids but not spiders), and crane flies (which are insects).

Appearance

Pholcids are fragile spiders, the body being 2–10 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 eyes. Eight and six eyes both occur in this family. Spermophora has a small globose 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. The shape of the Pholcus and Smeringopus's body resembles that of a peanut shell.

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 in undisturbed areas in buildings and cellars, hence the common name "cellar spiders". However, Pholcids are also quite commonly found in warm, dry places, such as household windows and attics.

Behavior

Trapping

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.

Threat response

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 and difficult to focus on. For this reason pholcids have sometimes been called "vibrating spiders", although they are not the only species to exhibit this behaviour. Doing so might make it difficult for a predator to see exactly where the spider is, may be intended to signal an assumed rival to leave, or may increase the chances of capturing insects that have just brushed their web and are still hovering nearby .[1] If the spider continues to feel harassed it will retreat into a corner or drop from its web and escape.

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 .[2][3] 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.[citation needed]

Close-up of a Cellar spider's head, showing two groups of three closely clustered eyes

Gait

Pholcus phalangioides often uses an alternating tetrapod gait (first right leg, then second left leg, then third right leg, etc.), which is commonly found in many spider species. However, frequent variations from this pattern have been documented during observations of the spiders’ movements.

Group Behavior

The grand-daddy longlegs has been observed in the wild to occasionally congregate en masse, particularly during the evenings when the weather is mild. This gathering, technically known as a "jamboree," allows the grand-daddy longlegs to enjoy banjo music, dancing, and social networking amongst its neighbors and kinfolk.

Systematics

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

The categorization into subfamilies follows Joel Hallan's Biology Catalog .[4]

Misconceptions

There is an urban legend stating that daddy long-legs spiders have the most potent venom of any spider, but that their chelicerae (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 long-legs" 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 medically significant 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.[5]

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 varies from about 0.5mm to 4mm), 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 by Alan Van Dyke has shown that pholcid venom is actually relatively weak in its effects on insects as well.[6]

According to Rick Vetter of the University of California at Riverside, the daddy long-legs spider has never harmed a human and there is no evidence that they are dangerous to humans.[7]

The urban legend ostensibly stems from the fact that the daddy long-legs spider is known to prey upon deadly venomous spiders, such as the redback, a member of the black widow genus Latrodectus.[8] By extrapolation, it was thought that if the daddy long-legs spider could regularly kill a spider capable of delivering fatal bites to humans, then it must be more venomous, and the uncate fangs were accused of prohibiting it from killing people.[9] In reality, it is merely quicker than the redback.[10]

References

  1. ^ Bruce Marlin (2006-04-25). "Video of the "vibrating spider" vibrating" (QuickTime Movie).
  2. ^ "Daddy Long Legs". Queensland Museum.
  3. ^ Wim van Egmond. "Pholcus phalangioides, the daddy-long-legs spider, in 3D".
  4. ^ Joel Hallan (2005-03-07). "Synopsis of the described Araneae of the world". Texas A&M University.
  5. ^ "Daddy Long Legs Site on UCR".
  6. ^ "The Spider Myths Site". Burke Museum. 2005-05-12.
  7. ^ Spider Myths-DaddyLongLegs
  8. ^ "FAMILY PHOLCIDAE - Daddy long-leg Spiders". Brisbane Insects and Spiders: The Expression of our Love of Nature. 2009. Retrieved 2009-11-13. {{cite web}}: External link in |publisher= (help)
  9. ^ "How to Kill a Venomous Spider". wikiHow. Retrieved 2009-11-13. {{cite web}}: External link in |publisher= (help)
  10. ^ "Daddy Longlegs". Tooter4Kids. Retrieved 2009-11-13. {{cite web}}: External link in |publisher= (help)
  • Pinto-da-Rocha, R., Machado, G. & Giribet, G. (eds.) (2007): Harvestmen - The Biology of Opiliones. Harvard University Press ISBN 0-674-02343-9
  • Platnick, Norman I. (2009): The world spider catalog, version 9.5. American Museum of Natural History.
Wikispecies has information related to Pholcidae.
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