Sociality

Subsociality is common in the animal kingdom. In subsocial taxa, parents care for their young for some length of time. Even if the period of care is very short, the animal is still described as subsocial. If adult animals associate with other adults, they are not called subsocial, but are ranked in some other classification according to their social behaviours. If occasionally associating or nesting with other adults is a taxon's most social behaviour, then members of those populations are said to be solitary but social. See Wilson (1971)[10] for definitions and further sub-classes of varieties of subsociality. Choe & Crespi (1997)[11] and Costa (2006)[12] give readable overviews.

Insect groups with subsocial species include:

• Dermaptera[13][14][15]
• Orthoptera
• Blattodea
• Zoraptera[16]
• Psocoptera[17]
• Embioptera[18][19]
• Hemiptera:[20][21] many families, including Membracidae,[22][23] Pentatomidae,[24] Reduviidae,[25][26][27] Tingidae.[28] Paternal care is known in some reduviids.[29]
• Thysanoptera
• Coleoptera.[30] Species and clades in multiple families:
  • Erotylidae[31]
  • Scarabaeidae[32][33]
  • Silvanidae
  • Tenebrionidae[34][35]
  • Gyrinidae
  • Passalidae;[36][37][38] the biology of Odontotaenius disjunctus (Illiger) is summarized by Bibbs et al.[39]
• Silphidae[40]
• Staphylinidae[41][42]
  • Curculionidae
  • Scolytinae[43][44][45][46]
  • Platypodinae,[47][45]
  • Other Curculionidae
• Chrysomelidae. In the leaf beetles, subsociality has been documented in two subfamilies, Cassidinae and Chrysomelinae.[48][49][50] In Cassidinae (43 tribes, 325 genera, c. 6000 species), maternal guarding of broods (eggs, larvae, pupae) is documented so far in two tribes (in the derived tortoise beetles clade[51]). In the Neotropical tribe Eugenysini, it appears in both Agenysa and Eugenysa.[52] In the tribe Mesomphaliini, subsocial species are documented in Acromis,[53] Omaspides, and Paraselenis. In Chrysomelinae (150 genera, c. 3000 species), maternal guarding of eggs and larvae is known in four tribes: Chrysomelini: Proseicela,[54] Doryphorini: Doryphora and Platyphora;[54] Gonioctenini: Gonioctena; and Phyllocharitini: Pterodunga mirabile in Australia.[55] See Chaboo et al. 2014 for a molecular-based phylogeny of Chrysomelinae and discussion of the origin of maternal care. Generally, reproductive and defence strategies in this subfamily are very diverse, with situations of ovoviviparity and viviparity and chemical defence.[56]
• Lepidoptera[57]
• Hymenoptera

The mouse lemur is a nocturnal, solitary-but-social lemur native to Madagascar.

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 the nocturnal strepsirrhine species and tarsiers. Solitary-but-social species include mouse lemurs, lorises, and orangutans.[58]

Sociobiologists place communal, quasisocial, and semisocial animals into a meta-class: the parasocial. The two commonalities of parasocial taxa are the exhibition of parental investment, and socialization in a single, cooperative dwelling.[4]

Communal, quasisocial, and semisocial groups differ in a few ways. In a communal group, adults cohabit in a single nest site, but they each care for their own young. Quasisocial animals cohabit, but they also share the responsibilities of brood care. (This has been observed in some Hymenoptera and spider taxa,[59] as well as in some other invertebrates.)[4] A semisocial population has the features of communal and quasisocial populations, but they also have a biological caste system that delegates labor according to whether or not an individual is able to reproduce.

Beyond parasociality is eusociality. Eusocial insect societies have all the characteristics of a semisocial one, except overlapping generations of adults cohabit and share in the care of young. This means that more than one adult generation is alive at the same time, and that the older generations also care for the newest offspring.

E. O. Wilson and Bert Hölldobler controversially[64] claimed in 2005 that humans exhibit sufficient sociality to be counted as a eusocial species, and that this enabled them to enjoy spectacular ecological success and dominance over ecological competitors.[65]