Explanation of Names
Anelosimus studiosus (Hentz, 1850)
(L). Be diligent; zeal (1)
A. studiosus occurs in se U.S. The two other U.S. species occur in Arizona or California.
e U.S., most records along the Gulf and Atlantic coast (TX-FL-CT-OK) south to northern Argentina (Draney, 2001),(BG data)
Females of Anelosimus cf. studiosus care for their egg-sacs and open them to allow the emergence of the spiderlings, which they feed by regurgitation.
The caterpillar of a Pyralid moth, Tallula watsoni
, is known to inhabit the web of this spider in Florida (Deyrup et al. 2004).
Only about 23 among more than 38,000 known spider species can be considered social!
Unlike social insects, where the workers are sterile and only the queen lays eggs, all social spiders in a colony are able to reproduce.
Deborah R. Smith of the University of Kansas at Lawrence compares social spiders to a pride of lions. "It's always interesting to see an organism one usually thinks of as asocial, predatory, and cannibalistic, forming large cooperative societies," says Smith.
Group living has its benefits, says Leticia Avilés of the University of Arizona in Tucson, who studies cooperative spiders in Ecuador. Working together, social spiders can capture prey as large as 10 times their size, whereas an individual spider is lucky to bag a bug twice as big as itself.
In some spider species the mothers care for the young well after they have hatched but do not establish colonies. Each generation of young goes off and makes its own single-family web. These species, Smith speculates, resemble forerunners to the fully social spiders. After some point in evolution, she says, "the babies just never leave home."
Social spider colonies have been found to have a female-biased sex ratio, sometimes as high as 9:1! This no doubt facilitates population growth during times of plenty.
A variety of other species live in association with the social spiders in their webs including 13 species of spiders and 11 species of insects.
Agnarsson, I. 2012. A new phylogeny of Anelosimus and the placement and behavior of Anelosimus vierae n. sp. From Uruguay (Araneae: Theridiidae). Journal of Arachnology. 40 (1): 78–84.
Darchen, R. & B. Delage-Darchen. 1986. Societies of spiders compared to the societies of insects
. Journal of Arachnology, 14 :227-238.