Sociality
Spiders exhibit varying levels of sociality. Whereas most spiders are solitary and even aggressive toward other members of their own species, some hundreds of species in several families show a tendency to live in groups, often referred to as colonies. These can form relatively long-lasting aggregations. Some of these aggregations can contain as many as 50,000 individuals as in the case of Anelosimus eximius (in the family Theridiidae). The level of sociality often varies between species (interspecies) but can vary within a species (intraspecies) as well. Many of these social spiders show cooperative brood care, use the same nest (web), and have some amount of generational overlap. A few species, such as Anelosimus eximius, exhibit reproductive division of labor. Some biologists argue that this classifies these species as fully eusocial as these non-reproductives can be considered a non-sterile worker caste. This reproductive division of labor is a result of resource availability and monopolization of those resources.
Read more about this topic: Spider Behavior