Overview

Brief Summary

The spider family Pholcidae (cellar spiders, daddylonglegs spiders) includes 1340 described species; the family is largely tropical, but several dozen species occur in North America north of Mexico, with the highest diversity in the southeastern United States (Huber 2005; Platnick 2013). In North America north of Mexico, six of the 12 genera found in this region are represented by introduced species only. Many pholcid species have adapted well to human habitats and are commonly found in corners and dark spaces in and around buildings, especially in basements. Pholcus phalangioides, for example, is common in buildings worldwide (Bradley 2013).

The cephalothorax of a pholcid is typically about as long as it is wide. The legs are extremely long and thin (this feature accounts for one of the common names for spiders in this family, "daddylonglegs spiders", although unlike daddylonglegs, which are not actually spiders, they spin webs). The legs have flexible tarsi that are usually held in a curved position. Most pholcids have eight eyes, although some have only six. When long-legged pholcids are disturbed in their web, they move rapidly, flexing their legs so that the body gyrates in a circular motion. This may make them difficult to see and perhaps difficult for their main predators, wasps, to capture (Bradley 2013). Short-legged pholcids can run rapidly (Huber 2005).

Pholcid females frequently carry their egg case in their chelicerae. The eggs are held together by a thin silken net and individual eggs are easily seen. The palps of adult males are very large and conspicuous. Web structure varies considerably within the family. Huber (2005) notes that the taxonomy of Nearctic pholcids is greatly in need of revision (this is presumably true for other regions as well). Much progress has been made, however, in understanding the higher level systematics and biogeography of the pholcids (Huber 2011; Dimitrov et al. 2013 and references therein). References cited in Dimitrov et al. (2013) provide an excellent entry into the pholcid literature.

  • Bradley, R.A. 2013. Common Spiders of North America. University of California Press, Berkeley.
  • Dimitrov, D., J.J. Astrin, and B.A. Huber. 2013. Pholcid spider molecular systematics revisited, with new insights into the biogeography and the evolution of the group. Cladistics 29: 132–146.
  • Platnick, N. I. 2013. The world spider catalog, version 14.0. American Museum of Natural History, online at http://research.amnh.org/entomology/spiders/catalog/index.html
  • Huber, B.A. 2005. Pholcidae. Pp. 194-196 in D. Ubick, P. Paquin, P.E. Cushing, and V. Roth (eds.) Spiders of North America: an Identification Manual. American Arachnological Society.
  • Huber, B.A. 2011. Phylogeny and classification of Pholcidae (Araneae): an update. The Journal of Arachnology 39:211–222.
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Introduction

Probably one of the spider genera best known to humans is the pholcid genus Pholcus. Commonly known as daddy-longlegs or cellar spiders, many species from this genus are synanthropic and often share our houses with us. Daddy-longlegs are even important characters in children's tales such as The Tale of Daddy-longlegs by Scott Arthur Bailey. However in some places "daddy-longlegs" is used when referring to harvestmen (Opiliones).

Pholcids show very high ecological plasticity and can be found everywhere, from deserts to humid tropical forests. Similar to many other arthropod groups the pholcids are most diverse in the tropical regions of the world. Several studies have shown that pholcids might be among the commonest if not the dominating web builders in some tropical regions (Manhart, 1994; Huber, 2000, 2003a). Currently there are 85 genera and 1000 species (Platnick, 2009) of pholcids but recent evidence shows that most of the diversity of this group is still unknown (Huber, 2000, 2003a, 2003b, 2003c, 2005a, 2005b, 2007).

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Comprehensive Description

Characteristics

Most pholcids are relatively small spiders with rounded prosoma and legs that usually are disproportionately long in relation to their body size. In some species legs may be over 20 times the body length of the animal. However, many leaf litter species have quite short legs. Pholcids are very variable in body shape and coloration but there are several diagnostic characters that distinguish them from other relatives. The most important are: the modified male palpal paracymbium called procursus, the sexual modifications of the male chelicerae and the pseudosegmentation of the leg tarsi.

Left: Prosoma of Pholcus edentatus frontal. Note the hornlike elevations on which lateral eye triads are placed. Center: Leg IV tarsus of Pholcus edentatus. Right: Male pedipalp of Pholcus ornatus. Note the conspicuously enlarged and modified paracymbium (procursus). Images © 2005 Dimitar Dimitrov

Pholcids have eight or six eyes. Eyes are arranged in two lateral triads and the anterior median eyes are placed in between, on the frontal part of the prosoma. In six-eyed species the anterior median eyes are absent. In some genera eyes are placed on conspicuous elevations of the prosoma. These often resemble a pair of horns, each one carrying one of the lateral eye triads. In many cave dwelling species eyes are further reduced in number and size and in many troglobite species eyes are completely lost.

The vast majority of pholcids build webs which vary greatly in size and complexity. Many species construct irregular three-dimensional webs but more ordered sheet webs are also no exception.

Reproductive biology in pholcids and functional morphology of their genitalia is fairly well studied (e.g., Gerhardt, 1921, 1923, 1924, 1927, 1929; Uhl et al., 1995; Eberhard and Briceño, 1983, 1985; Huber, 1994, 1995, 1997a, 1997b, 1998, 2002; 2004, 2006; Huber and Eberhard, 1997). Pholcids have a fairly complex courtship behavior and numerous male structures besides the pedipalps, such as modified cheliceral hairs and/or apophysis and in some cases even apophyses on the clypeus, are involved in the copulation.

Left: Holocnemus pluchei holding her eggs. © 2005 Cesare Brizio Right: Smeringopina bineti showing maternal care for her spiderlings. © 2008 Berhnard Huber

Pholcids lay few eggs, in some cases less than 10. Females do not make cocoons but carry the eggs in their jaws. Often, maternal care continues for some time after the spiderlings have hatched. Spiderlings have shorter legs in relation to their body size than adults, but after several molts leg-to-body-size proportion changes.

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Distribution

Geographic Range

There are hundreds of species of cellar spiders found all over the world. One species in particular, Pholcus phalangioides, is particularly comfortable living in houses and other buildings, and so has been spread all around the world by people moving around. Only a few species occur in Michigan, but they are common in basements and unused buildings.

Biogeographic Regions: nearctic (Native ); palearctic (Native ); oriental (Native ); ethiopian (Native ); neotropical (Native ); australian (Native )

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Physical Description

Morphology

Physical Description

Like all spiders, cellar spiders have two body-segments, a cephalothorax in front and an abdomen behind. They have eight legs, all attached to the cephalothorax. Cellar spiders have very long thin legs compared to other spiders. Their legs are many times longer than their bodies. Because of this they are sometimes called "daddy longlegs spiders", though they are not related to the other "daddy longlegs," which are Harvestmen. On the front they have two small "mini-legs" called palps. These are used to grab prey, and in mating, and are much bigger in male spiders than in females.

Different species of cellar spiders have six or eight eyes, and the size and arrangement of eyes is different in different groups. Cellar spiders have fangs that they use to bite their prey with, and have venom glands, but their fangs are very short. Their color varies from light tan to grayish-brown.

Female cellar spiders are often much bigger than males.

Range length: 2.0 to 10.0 mm.

Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry ; venomous

Sexual Dimorphism: sexes alike; female larger

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Ecology

Habitat

These spiders prefer to live in dark places: in caves, cracks and crevices in rocks, unused animal burrows, and in the dark and quiet parts of buildings.

Habitat Regions: temperate ; tropical ; terrestrial

Terrestrial Biomes: taiga ; chaparral ; forest ; rainforest ; scrub forest ; mountains

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Trophic Strategy

Food Habits

Like all spiders, cellar spiders are predators. They eat Insecta, Araneae, and other small invertebrates. They spin a large loose, three-dimensional web (not flat like orbweavers) that is not sticky. They use their web as a kind of prey-detection system. When a passing insect bumps into it, they come running out and grab it and bite it, then wrap it in silk. Formicidae are particularly common prey.

Many cellar spiders also raid the webs of other spiders, eating their prey and the spiders themselves. They sometimes hunt around the edges of the webs of female spiders of other species. Males who come to mate with the female may get eaten by the cellar spider instead.

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Associations

Predation

Cellar spiders mainly avoid predators by living in dark places. If their web is touched, they sometimes vibrate back and forth very fast. We don't know for sure why they do this, maybe to make themselves harder to see.

Known Predators:

  • other Araneae 
  • Hymenoptera
  • Chilopoda
  • small Squamata 
  • small mammals especially Soricidae 

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Life History and Behavior

Behavior

Communication and Perception

Spiders in this group probably use touch and chemicals to communicate, though they can see too. They are also very sensitive to vibrations in their webs.

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Life Cycle

Development

Cellar spiders hatch from eggs, and the hatchlings look more or less like grown-up spiders, though sometimes their colors change as they age. To grow they have to shed their exoskeleton, which they do many times during their lives.

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Life Expectancy

Lifespan/Longevity

We don't know for sure how long these spiders live, probably only a few years at most, and very few probably make it that long.

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Reproduction

Not much is known about reproduction in this group of spiders.

Breeding season: unknown

Key Reproductive Features: sexual ; fertilization (Internal ); oviparous

Female cellar spiders form their eggs into a ball. They hold the ball in their jaws for several weeks while the eggs develop, and when they new spiders hatch, they ride on their mother for several days before dispersing.

Parental Investment: female parental care

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Evolution and Systematics

Evolution

Discussion of Phylogenetic Relationships

View Pholcidae Tree

Tree from Bruvo-Madaric et al. (2005)

Despite important advances in recent years (Huber, 2000; Bruvo-Madaric et al., 2005) the family level phylogeny of pholcids is still a work in progress. Several subfamilies of pholcids have been named but their limits remain elusive. The phylogenetic hypothesis illustrated above is derived from the only family-wide phylogenetic study that includes molecular and morphological data (Bruvo-Madaric et al., 2005).

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Molecular Biology and Genetics

Molecular Biology

Statistics of barcoding coverage

Barcode of Life Data Systems (BOLD) Stats
                                        
Specimen Records:1,024Public Records:312
Specimens with Sequences:621Public Species:111
Specimens with Barcodes:433Public BINs:89
Species:146         
Species With Barcodes:78         
          
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Barcode data

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Locations of barcode samples

Collection Sites: world map showing specimen collection locations for Pholcidae

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Conservation

Conservation Status

No cellar spider species are known to be endangered.

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Relevance to Humans and Ecosystems

Benefits

Economic Importance for Humans: Positive

These spiders are not dangerous to people, and they sometimes eat insects that are pests to humans.

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Wikipedia

Pholcidae

Pholcidae, commonly known as cellar spiders, are a spider family in the suborder Araneomorphae.

Some species, especially Pholcus phalangioides, are commonly called daddy long-legs spider, granddaddy long-legs spider, carpenter spider, daddy long-legger, or vibrating 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[edit]

Pholcids are fragile arachnids, 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.

Habitat[edit]

Pholcids are found in every continent in the world besides Antarctica where it is too cold for them to survive. 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[edit]

Trapping[edit]

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[edit]

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[edit]

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[edit]

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.

Systematics[edit]

Two Crossopriza lyoni. The bottom one is male. The female is clutching her egg bundle (magnified).
Smeringopus pallidus female with egg sac.
A marbled cellar spider (Holocnemus pluchei) carrying prey.
Male shortbodied cellar spider (Spermophora senoculata) from the United States

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[edit]

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 episode 13 - "Buried in concrete".[6] Hosts Jamie Hyneman and Adam Savage first established that the spider's venom was not as toxic as other venoms, after being told about an experiment whereby mice were injected with venom from both a daddy long-legs and a black widow, with the black widow venom producing a much stronger reaction. After measuring the spider's fangs at approximately 0.25 mm (average human skin thickness varies from about 0.5mm to 4mm), Adam Savage allowed himself to be bitten, and reported that the bite produced little more than a mild short-lived burning sensation. This appears to confirm that, contrary to popular belief, pholcid bites can penetrate human skin but will deliver a harmless envenomation. Additionally, recent research by Alan Van Dyke has shown that pholcid venom is relatively weak in its effects on insects as well.[7]

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.[8]

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.[9] 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.[10] In reality, it is merely quicker than the redback.[citation needed]

References[edit]

  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. ^ "Myth Files on the Discovery site". Discovery channel. 
  7. ^ "The Spider Myths Site". Burke Museum. 2005-05-12. 
  8. ^ Spider Myths-DaddyLongLegs
  9. ^ "FAMILY PHOLCIDAE – Daddy long-leg Spiders". Brisbane Insects and Spiders: The Expression of our Love of Nature. 2009. Retrieved 2009-11-13. 
  10. ^ "How to Kill a Venomous Spider". wikiHow. Retrieved 2009-11-13. 
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