Meet Anelosimus studiosus, the southeastern social cobweb spider. This minuscule (7mm) speck on a car window turned out to be a member of one of only 23 social species out of approximately 38,000 known species of spiders. Their behavior varies by region, and in Florida they’re relatively rarely social, but in, say, Texas, you can find semi-permanent webs with multiple generations of spiders living communally.
Social spiders are not like ants or bees, where there is only one reproductive female — all spiders in a colony can reproduce. The colonies have been likened to a pride of lions, not only because of how the females group together to cooperatively hunt and raise young, but because lions are also a social exception to a family (Felidae) which is traditionally solitary. Researchers in Florida studied multiple social spider nests and found that juvenile spiders in colonies survived longer, developed faster, and had more resources than did solitary juveniles. Mothers in groups survived longer and produced second broods earlier than solitary mothers. In addition, spiders working together can capture much larger prey than solitary ones.
Social spider colonies are also somewhat like lion prides in that they often have more females than males. This setup would facilitate population growth during times of plenty. (When resources are scarce, massive social webs are not found.) On the downside, the tendency of females to remain in these massive groups has been found to result in highly inbred populations, which may be why more spider species are not social.