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Sociality is a survival response to evolutionary pressures. For example, when a mother wasp stays near her larvae in the nest, parasites are less likely to eat the larvae. Biologists suspect that pressures from parasites and other predators selected this behavior in wasps of the family Vespidae.
This wasp behaviour evidences the most fundamental characteristic of animal sociality: parental investment. Parental investment is any expenditure of resources (time, energy, social capital) to benefit one offspring. Parental investment detracts from a parent's capacity to invest in future reproduction and aid to kin (including other offspring). An animal species that cares for its young but shows no other other sociality traits is said to be subsocial. Subsociality is common in the animal kingdom.
An animal that exhibits a high degree of sociality is called a social animal. The highest degree of sociality recognized by sociobiologists is eusociality. A eusocial species is one that exhibits overlapping adult generations, reproductive division of labor, cooperative care of young, and—in the most refined cases—a biological caste system.
Solitary animals, such as the jaguar, don't associate except for courtship and mating. If an animal species shows a degree of sociality beyond courtship and mating, but lacks any of the characteristics of eusociality, it is said to be presocial. Presociality is much more common than eusociality.
Parasociality is a degree of presociality in which individuals of the same generation live in a single, cooperative dwelling and interact. Sociobiologists and entymologists generally acknowledge three kinds of parasocial groups: communal, quasisocial, and semisocial.
|Degree of sociality||Parental investment||Members of only one adult generation and their young cohabit||Cooperative care of young||Reproductive division of labour||Caste system||Overlapping adult generations|
|Solitary but social||Yes||Maybe||No||No||No||No|
Charles D. Michener published a classification system for presociality in 1969, building on the earlier work of Suzanne Batra (who coined the words eusocial and quasisocial). Michener used these terms in his study of bees, but also saw a need for additional classifications: subsocial, communal, and semisocial. In his use of these words, he did not generalize beyond insects. Certain species of insects are the only animals known to exhibit semisociality and eusociality.
In a communal group, adults cohabit, but they each care for their own young. Quasisocial animals additionally share the responsibilities of brood care. Semisocial insects cohabit, care cooperatively for young, and also have a caste system. In eusocial insect societies, overlapping generations cohabit and share in the care of young.
Solitary-but-social animals forage separately, but some individuals sleep in the same location or share nests. The home ranges of females usually overlap, whereas those of males do not. Males usually do not associate with other males, and male offspring are usually evicted upon maturity. Among primates, this form of social organization is most common among nocturnal, prosimian species. Examples of species that can be categorized under this type of social organization include mouse lemurs, lorises, and orangutans.
Quasisocial means co-operative brood care by a single generation of adults in a common nest site. It differs from eusociality by not having reproductive caste differentiation and generational overlap.
The term quasiocial was introduced in 1966 by Suzanne Batra and given a more definitive meaning by E. O. Wilson. as one of the four categories of insect social behaviour. Quasisocial behaviour has been observed in some Hymenoptera and spider species, as well as in some other invertebrates.
The social groups of all eusocial animals have overlapping adult generations, cooperative care of young, and division of labor. However, in some animal species the division of labour is more flexible than in others. An individual's duty is dictated by caste, but one's caste may change.
For example, a queen bee can become a worker bee, and a worker bee can become a queen bee. The individual has a social role, and that role is not codified in the shape of the organism (its morphology). When organisms in a species are born with physical characteristics specific to a caste, and that caste never changes in the life of the organism, this exemplifies the highest degree of sociality. Only two orders in the animal kindgom are highly eusocial: Hymenoptera (ants, bees, sawflies, and wasps) and the infraorder isoptera (termites). Eusocial species that lack this criterion of morphological caste differentiation are said to be primitively eusocial.
- Smelser, Neil J.; Baltes, Paul B., eds. (2001). "Evolution of Sociality". International Encyclopedia of the Social & Behavioral Sciences. New York: Elsevier. p. 14506. ISBN 9780080430768. OCLC 47869490.
- Ross, Kenneth G.; Matthews, Robert W. (1991). The Social Biology of Wasps. Ithaca: Comstock Publishing Associates. ISBN 9780801420351. OCLC 22184337.
- Gadagkar, Raghavendra (September 1987). "What are social insects?" (PDF). IUSSI Indian Chapter Newsletter (International Union for the Study of Social Insects) 1 (2).
- Michener, C. D. (1969). "Comparative Social Behavior of Bees". Annual Review of Entomology 14: 299–342. doi:10.1146/annurev.en.14.010169.001503.
- Sussman, R. W. (2003). "Ecology: General Principles". Primate Ecology and Social Structure. Pearson Custom Publishing. p. 29. ISBN 978-0-536-74363-3. OCLC 57408633.
- http://phoenix.nal.usda.gov/bitstream/10113/39270/1/IND44289070.pdf[dead link]
- Batra, S. W. T. (1966). "Social behavior and nests of some nomiine bees in India (Hymenoptera, Halictidæ)". Insectes Sociaux 13 (3): 145–153. doi:10.1007/BF02223020.
- Wilson, E. O. (1971). The Insect Societies. Cambridge: Belknap Press. ISBN 9780674454903. OCLC 199513.
- Furey, R. E. (1998). "Two cooperatively social populations of the theridiid spider Anelosimus studiosus in a temperate region". Animal behaviour 55 (3): 727–735. doi:10.1006/anbe.1997.0648. PMID 9515053.