The long-legged cellar spider


Biology of Pholcus phalangioides


Essay
Author: Kurt Stüber
dedicated to F.A.
Scanned picture of Pholcus phalangioides (100 bpi).
Enlarged version (300 bpi, 23144 Bytes).
Giant version (1000 bpi, 135355 Bytes).
You may wonder how to scan a spider. First you cut a hole into your mousepad and place it on the scanner. Then you convice the spider to sit there too and then you close the cover. After a dozen trials you may be able to successfully scan the spider when its tired of moving around. The spider above survived this process unharmed and is probably still sitting in some corner of my office waiting for prey. They may live up to 3 years!
Long legged cellar spiders are one of the most common spiders in households and have a worldwide distribution. They have been reported from American, European, Asian and Australian houses, Italian caves and Korean volcanoes. Their scentific name is Pholcus phalangioides (Fuesslin, 1775). Pholcus are fragile spiders with very long legs and an elongated body. Body and legs are almost translucent and with a microscope the movement of blood cells in legs and other body parts can be followed in a live animal.

Net
The nets of Pholcidae are irregular arched constructions forming a kind of baldachin, where the spider resides on the lower side hanging downwards! Anything that touches the net is attacked and taken for prey if its not too big.

Feeding
Cellar spiders feed on any insects that is unfortuante enough to stumble over their net silk. But Pholcus phalangioides is also known to invade other spider's nets and attack the original inhabitants. They then use the foreign to net to catch prey. If the old inhabitant left an enwrapped prey, this too will be taken by the invader.
A prey is swiftly wrapped with new silk. This may well be several meters of silk which is spun around and around using the legs number 4 (i.e. the 4th pair of legs). Then the prey is bitten and digesting fluid injected. The sucking and emtying may take a whole day. The spider is able to empty a fly by sucking at the tip of a leg, an display of an enormous sucking power!

Whirling
As a means of defense the spiders have developed a method of self-camouflage by whirling their bodies around with the legs firmly attached to the net ("zittern" in German). To an observer this obscures the spider from sigth, making them almost "invisible". You may envoke the whirling by touching the net or the spider.

Mating
Two spiders mating. Mating can take hours. During this process male sperm is transferred to the female into a special cavity at the beginning of the uterus (uterus externus). There the spermatozoa remain until they are used to fertize the egge. When the actual egg laying takes place is largely dependant on the availability of food.

Eggs
Female Pholcus phalangioides carrying a package with her eggs.

Offspring
Female in its net with about 20 prenymps that have hatched from their eggs. From the eggs prenymps hatch which are mostly passive and guarded by their mother. After about 9 days the prenymphs shed their old skins and little spiders appear which leave the maternal net and look for a new place to build their own.

Literature

Correspondence:
On July 20 and 21 I received an email from Ingrid W. from California confirming the worldwide distribution of Ph. phalangioides and with observations on molting behaviour.


This page is part of the Kurt Stüber's home page.
The URL of this page is http://www.mpiz-koeln.mpg.de/~stueber/essays/pholcus_phalangioides.html
For personal comments please write to the author(s) of this page or to Kurt Stueber.
This page has last been modified on July 21, 1999.