Czechowski, W. 2004: Scarcity of sites suitable for nesting promotes plesiobiosis
in ants (Hymenoptera: Formicidae). - Entomol. Fennica 15: 211–218.
Plesiobiosis is a rudimentary form of social symbiosis. It consists of the close proximity of nests of different social insect species. Numerous cases of plesiobiosis between ant species observed in a successional series of rocky habitats in S Finland are listed and the most interesting of them are described in detail. Among all Lasius colonies found within the whole successional series studied, as many as 8.4% were plesiobiotically associated with other ants. In the two earliest successional stages: the shore meadow and the open rocky outcrop, the proportion was nearly 12% and 10% respectively. The finding of numerous plesiobiotically related nests there is discussed in the context of the unique local habitat conditions.