Posted by Wendy Allanbrook on March 1, 2006

Q: A spider has built her web in my south-facing window in Oakland, CA. She is a little under two inches in girth, brown, with pebbly white markings on her back, and skinny legs. I have grown fond of her, and watch her carefully, although I have had no prior interest in spiders, only the usual mild fear. Until last night, she would leave the web several times a day and then return to its center. I have never seen an insect fly into the web, or her consuming anything in the web, so I assumed she must feed elsewhere. Last night she returned and seemed very clumsy, almost as if she were injured. Then I realized she had a large bolus with her, seemingly wrapped in white, about the size of a housefly. She finally positioned herself in the center of the web holding the bolus—a very awkward process. This morning the bolus is gone, and she seems fatter, her legs pulled inward and curled toward her body. Was the bolus food? An egg case? If food, why is this the first time I have seen her eat in her web? How does she eat, and where? When should I expect her to give birth, and what should I look for?

Thanks in advance! P. S. Wouldn't you know—with stunning originality I've named her Charlotte.

Habitat: suburban/yard

State: California

Habitat: suburban/yard

A: You've discovered, what everyone should learn, - spiders are really interesting animals. I'm not entirely sure what is going on since spiders often wrap up their prey in webbing but also roll up their eggs in a ball of web too. Since your spider has a web, she should be catching any food there rather than ranging beyond for food. I could easily believe that your spider has an egg mass rather than food. If it is food, she'll eat it rather soon and then dump it out of her web but if it is an egg mass, I think she'll protect it for several days, if not a week or more. If these are eggs and they hatch, you'll have lots of tiny spiders in the web. Be sure the young have access to the outside and they'll be able balloon (travel on the wind) beyond your home to establish their own web. Good luck and enjoy.

John Wiessinger ( March 3, 2006)