[The specialisation in ant working groups involved in trophobiosis with aphids]

The peculiarities of behaviour and organization of taking care of aphids while trophobiosis were studied in ant species predominant in milti-species communities (Formica polyctena Forst, F. aquilonia Yarr., and F. pratensis Retz.). "Professional specialisation" with distinct division of segregation functions of aphid colony protection and honeydew collecting was revealed and described in working groups of ants, which are constant in composition. It is shown that trophobiont working groups include both passive and active foragers. The functions of the former are usually limited to honeydew collecting and transportation. Active foragers are multifunctional: in addition to their basic duties, they may defend symbionts, search for new aphid colonies, and, to some extent, coordinate group activities. It was shown earlier that ants employ different schemes of interactions with aphids, from individual foraging to "professional specialisation" in working groups. Comparative analysis of the schemes of interactions between ants of different species and aphids has shown that the degree of functional differentiation in trophobiont working groups is conditioned by carbohydrate food requirements of the colony. Ant colony size and the condition of available resources (abundance and productivity of symbionts) are the principal factors that determine the emergence of strict specialisation in groups. The trend to further differentiation of functions in trophobiont working groups is observed under increasing ant colony size and under food deficiency; such strict specialisation is facultative.