Current Issue

Bug of the Week is written by "The Bug Guy," Michael J. Raupp, Professor of Entomology at the University of Maryland.

Spiders in corners, part 2: Cellar spider, Pholcus phalangioides


It’s easy to see why cellar spiders are often called daddy-long-legs.


With the holiday season fast approaching and family and friends soon to visit, the Bug Guy received   orders to prepare the spare bedroom in the basement for overnight guests. Part of the assignment was to inspect windows and remove any arthropods living or dead that might terrorize visitors who do not share affection for animals lacking fur and possessing more than four legs. Near the corner of one dimly lit window, I discovered a diverse collection of tiny insect carcasses and didn’t have to look far to see a gangly and beautiful cellar spider hiding in the upper corner of the window. In last week’s episode, we met the common house spider that exploits outdoor window frames to string her web and capture prey. Just on the other side of the glass, the cellar spider employs the same strategy for trapping small insects drawn to the light of a window in a futile attempt to escape the confines of a basement. Beneath the web, exsanguinated bodies of small flies, pill bugs, and beetles piled up on the window sill.

A pile of tiny insect carcasses often mark the spot of a cellar spider’s lair.

Cellar spiders are found throughout much of the world in temperate and tropical regions. Millions of years ago cellars were noticeably absent from the planet, but caves and dank tree hollows were aplenty and cellar spiders found these habitats perfect for building their loose webs for snaring prey. In the land down under and some other parts of the world, cellar spiders go by the name of daddy-long-legs, a moniker associated with another arachnid, opilionids, which we met in a previous episode.  I have handled cellar spiders and never been bitten and if this rare event did happen, the spider’s bite is reported to be harmless to humans. However, the cellar spider can bring down formidable spiders including Australian redbacks, kin to our black widow, and the fearsome huntsman who we will meet in an upcoming episode.

Mating is a curious affair in many spiders, including Pholcus. Male cellar spiders deposit a droplet of sperm onto small web, which is then gathered and stored in an appendage called the pedipalp. He then deposits the sperm into a cleft in the female’s abdomen where sperm will be stored until the females uses the little wigglers to fertilize her eggs. Female cellar spiders are not necessarily “you and only you” kinds of gals and will often mate with more than one fella. In the spider mating game, it turns out that sperm from the last mating are the ones most likely to fertilize eggs. So, to ensure that he will be the proud father of spiderlings, the male removes sperm placed by his betrothed’s last suitor before he makes his deposit. What a guy. After all this drama, the female lays eggs and encases them in a thin cloak of silk. The egg bundle is toted about in their mother’s jaws to reduce the likelihood of being discovered and eaten by tiny predators. Like wolf spiders we met in a previous episode, tiny spiderlings also hitch a ride with mom for a short period of time after hatching.


With her egg case snugly tucked beneath her body, the mother cellar spider rocks out when disturbed by a predator or bug geek. Rocking the web is believed to be an anti-predator behavior in many spiders.

If holiday cleaning is on your to-do list, before you attack those basement windows with vacuum or duster, take a moment to observe and enjoy these helpful predators in the corners. Maybe convince your spouse to let them enjoy one last Thanksgiving feast before you toss them out.  


Bug of the Week thanks Dr. Jeffery Shultz for identifying the spider featured in this episode; and Dr. Nancy Breisch and the Bartley Raupp’s for providing inspiration and guidance for spider stories.

References used in this episode can be found at the websites below: