Long-bodied Cellar Spider

Appearance

"Pholcus phalangioides" are sexually dimorphic, where females are slightly larger than the males of the species. The body length of this species varies between males and females. Males tend to be around 6 to 10 mm in length with the average male being around 6 mm. The average female ranges from 7 to 8 mm in length. As indicated by their common name, "daddy long-legs", these spiders boast eight very long and thin legs which are covered in thin, grey bristles. On average, their legs are roughly 5 to 6 times as long as the spider's body. The average length of an adult female's legs is roughly 50 mm.

The bodies of "P. phalangioides", as with all spiders, can be divided into two parts: the prosoma and the opisthosoma. The prosoma is commonly known as the cephalothorax, and the opisthosoma is commonly known as the abdomen. The opisthosoma is considered the posterior part of the body which contains most of the spider's internal organs. The round, peanut-like shape of the spider's cephalothorax has earned the species the nickname "skull spider". The translucent bodies of "P. phalangioides" tend to be a grey-pale brown color with a dark spot on the back of the prosoma and some dark, blurred spots on the dorsal side of the opisthosoma.          

Although some other members of the family Pholcidae have six eyes, "Pholcus phalangioides" is an eight-eyed spider. The eyes are arranged such that there is a pair of smaller, dark eyes at the front of the prosoma followed by three parallel rows of pairs of larger eyes.

Similar to other species of spider, a hard exoskeleton coats the bodies of "P. phalangioides". Depending on the age of the spider, this exoskeleton must be shed at differing intervals; younger spiders tend to molt much more often. During molting, the spider will produce certain enzymes that release the rest of its body from the underlying tissue of its exoskeleton. The spider is then able to escape the exoskeleton. The remnant outer skin or exoskeleton is known as the exuviae.

It takes about one year for these spiders to mature after they are born, and their life span is up to two years post-maturity.

Distribution

The population sizes of "P. phalangioides" are influenced greatly by the presence of human-made buildings since these spiders prefer warmer habitats indoors. The large number of buildings in the world has favoured "P. phalangioides", though populations tend to be relatively small, widely dispersed, and greatly isolated from one another. This small size combined with low mobility of populations results in an increased importance placed on the role of genetic drift, more specifically the founder effect, on population structure. Although some gene flow does exist between populations, its importance has been insignificant when compared to that of geographical isolation-driven genetic drift. As a result, most "P. phalangioides" individuals of the same population that live in the same geographical region will have a very low degree of genetic variation. On the other hand, this genetic drift results in significant interpopulation differentiation.Because of its spread with humans worldwide, there has been some uncertainty about its exact original, native range, although it has been recognized as being likely in the subtropical parts of the Old World, thus with a preference for warmer climates, and recent authorities regards it as only native to Asia. As a synanthropic species, "Pholcus phalangioides" has largely had its modern geographic distribution determined by the spread of humans around the world. Today, these spiders can be found on every continent in the world.

"P. phalangioides" are not suited for survival in cold environments which is why they in these regions prefer the warmth of the indoors, specifically inside human dwellings. These spiders have a particular affinity for dimly lit, dark areas that are quiet and calm. They are commonly found in the corners of buildings and people's homes as well as in attics. Populations of "Pholcus phalangioides" living outdoors can be found in caves and in between rock crevices.

Behavior

The extent of the "P. phalangioides" communication is seen in times of mating. The primary form of communication for these spiders is through the use of touch and chemicals, specifically pheromones.The primary defense strategy performed by "P. phalangioides" in moments of predation is whirling. Whirling, or a gyration of the body, consists of the skull spider swinging its body around in a circle repeatedly while its legs remain fixed on the web. This whirling strategy is induced as soon as the individual recognizes any sort of movement occurring in its web. The duration of this whirling is related to the specific kind of predator that the skull spider encounters. Short-duration whirling can be induced simply by a human touching the skull spider's web or occasionally by spider of a different species. Long-duration whirling, which can last several hours or even days, is performed specifically in response to the presence of the more threatening Salticid, or jumping spiders, much more often than for spiders of other families. The rapid gyrating associated with the whirling disturbs the vision of the Salticid spiders such that they can no longer rely on their acute eyesight to pinpoint the location of "P. phalangioides". This disruption results in the safety of the skull spiders from an otherwise deadly predator.

Habitat

Because of its spread with humans worldwide, there has been some uncertainty about its exact original, native range, although it has been recognized as being likely in the subtropical parts of the Old World, thus with a preference for warmer climates, and recent authorities regards it as only native to Asia. As a synanthropic species, "Pholcus phalangioides" has largely had its modern geographic distribution determined by the spread of humans around the world. Today, these spiders can be found on every continent in the world.

"P. phalangioides" are not suited for survival in cold environments which is why they in these regions prefer the warmth of the indoors, specifically inside human dwellings. These spiders have a particular affinity for dimly lit, dark areas that are quiet and calm. They are commonly found in the corners of buildings and people's homes as well as in attics. Populations of "Pholcus phalangioides" living outdoors can be found in caves and in between rock crevices.

Food

"P. phalangioides" are carnivorous predators that feed on insects, other spiders, and other small invertebrates. Unlike many other spiders, who simply feed on prey that have gotten stuck in their webs, these spiders frequently venture out from their own webs to hunt other spiders resting in their respective webs and feed on them or their eggs. In times of low prey availability, both the males and females of the species will turn to cannibalism to meet their nutritional needs.

Predators

This species is preyed upon by jumping spiders of the Salticidae family. Some of these spiders simply leap into the webs of their prey and attack them. Others, employ a certain strategy known as mimicry in order to trick "P. phalangioides" and capture them.

A jumping spider species whose aggressive mimicry behavior towards "P. phalangioides" has been well studied is the "Portia fimbriata" jumping spider species of the genus "Portia". During mimicry, the jumping spider produces certain specialized vibrations near the edge of the webs of "P. phalangioides." These vibrations cause the webs of "P. phalangioides" to oscillate in such a way that they mimic the oscillations that would be produced when a form of prey gets stuck in the web. The jumping spider will then continue on with these vibrations for very long durations of time, up to three days in some instances. "P. phalangioides" often assume that this is an indication that they have caught some sort of prey and will move toward the host of the vibrations. At this point, the jumping spider is in an optimal position to leap onto and attack "P. phalangioides", thus subduing them in many instances. In addition to employing mimicry, these jumping spiders are also particularly good at preventing "P. phalangioides" from inducing their whirling defense mechanism, which tends to be an effective way for "P. phalangioides" spiders to defend themselves from predators.

Defense

Although these spiders are capable of hunting and killing some of the most venomous spiders in the world such as the redback spider, they are not dangerous to humans. According to researchers Greta Binford and Pamela Zobel-Thropp, the effects of "P. phalangioides" venom on humans and other mammals are negligible. In humans, the "P. phalangioides" bite simply results in a mild stinging sensation that has no long-term health consequences. A recent study has even shown that Pholcidae venom has a relatively weak effect, even on insects.