EPOW - Ecology Picture of the Week

Daddy Long-legs or Cellar Spider (Pholcus aff. phalangioides)
Class Arachnida, Order Araneae, Family Pholcidae
eastern Oregon USA

Explanation:  On a recent research outing to eastern Oregon to study invertebrates of burned and old-growth forests, my field assistant and I stayed in a remote cabin.  At night, dangling inverted over the bed in my assistant's room was this lovely and fragile spider, waiting in its crudely-designed web for some unwary insect to enter its lair.

This is a very common and interesting but usually overlooked organism ... that goes by more names than it has legs:  daddy long-legs spider, cellar spider, long-bodied cellar spider, vibrating spider, house spider, and others.  The better names are cellar spider, because they tend to hang out (literally) in dank corners of dark rooms ... or vibrating spider, because when disturbed it rapidly shakes its web, perhaps to avoid being preyed upon.    

Cellar spiders indeed have "long legs" which are quite
fragile and may break off but do not grow back.

In the forest, you can find cellar spiders under rocks and tree bark and in old burrows of mammals.  They have been known in North America for a very long time, but might have originated from Europe and inadvertently introduced long ago.

They feed on small insects including Tegenaria spiders which include the deadly hobo spider (Tegenaria duellica), and thus provide a service to humans.  

Long ago, it was Aristotle who wrote of spiders that spin such irregular, tangled webs and he wrote:  

There are two kinds of spiders which spin thick webs, the larger and the smaller.  The one has long legs and lies in wait hanging upside down on its web [probably Pholcus or the cellar spider]. Because of its large size, it cannot readily conceal itself so it keeps underneath, so that its prey may not be frightened off, but may strike upon the web's upper surface.

 Whether Aristotle had a cellar is not documented.

Information:
     Acorn, J., and I. Sheldon. 2001. Bugs of Washington and Oregon. Lone Pine Publishing, Edmonton, Canada. 160 pp.
     Emerton, J. H. 1961. The common spiders of the United States. Dover Publications, Inc., New York.  227 pp.
     Hillyard, P. 1994. The book of the spider: a compendium of arachno-facts and eight-legged lore. Avon Books, New York. 218 pp.
     Milne, L., M. Milne, and S. Rayfield. 1980. National Audubon Society field guide to North American insects and spiders. Alfred A. Knopf, New York. 989 pp.