Monday, August 17, 2015

Long-bodied Cellar Spider

Spreading out on the wall - REK
After years of watching these leggy spiders crawl all over the bathroom in our creek house, I thought it was time to give them their day in the sun.  After all they spend the rest of their lives sequestered in dark, damp places asking for nothing and bothering no one, unless it is a house guest too polite to mention them.  For the most part they just hang on a wall or slowly explore the tile floor, looking for tiny pests that we don't even know exist.

This is the Long-bodied Cellar Spider, Pholcus phalangioides, the most common of the Pholcidae or cellar spiders.  They have a number of common names including daddy long-legs spider, granddaddy long-legs spider, carpenter spider, and vibrating spider. Their bodies are 5-8 mm long, (less than 1/3") and their leg are 8 times longer.

"Daddy Longlegs" Crane Fly- Six legs of an insect  - REK
Crane fly - Limonia - REK
Their "daddy long-legs" name is appropriate but can be confusing.  This common name is also applied to both harvestmen of the Opilione class and to crane flies which are sometimes mistaken for giant mosquitoes.  Crane flies have 6 legs like all insects and wings typical of all the Diptera (true flies).


Long-bodied spiders have three distinct body parts (head, thorax and abdomen) while the Opiliones (harvestmen) have the head and thorax fused into one small part frequently making their bodies appear oval.  Both have eight legs typical of the Arachnids.

Harvestman - REK
Long-bodied Cellar Spider - REK
They originated in the sub-tropics but are now found on every continent, probably traveling along with the commerce of humans.  They do not tolerate cold but have found their niche in warm human habitats.  In their original lands they reproduce annually in the warm season while in our house it is always the season to reproduce and life is good.

Skull shaped head with two sets of three round eyes tightly clustered together - REK
Because of the shape of their thorax they are also commonly called a "skull spider."  Another defining characteristic of various spider species is the placement of their eyes.  In this case there is a set of three round raised eyes clustered on both sides of the head as well as another pair in front.

Female with egg case - Olei CC- Wikimedia
A female produces 20-30 eggs which she will patiently carry around in her pedipalps until the young hatch.  The young will molt six times before they reach maturity

Mother and babies - Luis Fernández García via Wikipedia
Their webs are irregular, messy but very small, tending to cling to a wall or other horizontal surface.  When they perceive a threat they start vibrating on their web, making them harder to see, thus the "vibrating spider" name.

Long-bodied spiders have very weak venom and are barely able to pierce human skin, with only a temporary discomfort.  On the other hand, they are considered beneficial as they are predators of many venomous spiders that are threats to us.  As we see an occasional brown recluse in the nooks and crannies, letting these leggy creatures patrol the house is a small price to pay.

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