Trophallaxis in weakly social bees ( A poidea)

The hypothesis that trophallaxis, the transfer of symbionts, nutrients, and semiochemical signals within groups, functions as a social glue to bind group members together can be traced to ideas of the ‘social stomach’ developed by Rouboud, Janet and Forel, and popularised by Wheeler (1928) (see Sleigh, 2002 for references and a history of ideas relating trophallaxis to sociality). Recently, Nalepa (2015a) argued that a critical factor in the evolution of termite eusociality was the occurrence of trophallaxis, as it would help integrate ‘social, nutritional and microbial environments’. This publication stimulated an exchange of ideas about the merits of this argument, which centred in part on the potential benefits and costs of trophallaxis, its occurrence in extant relatives of termites, and the relative important of other traits (Korb, 2015; Roisin, 2015; Nalepa, 2015b). Does a consideration of the benefits and costs of trophallaxis for the evolutionary origins of sociality in bees shed light on this exchange? Ample evidence indicates that trophallaxis represents an important societal-level benefit in the evolutionary elaborations of bee sociality, at least in some lineages. In the obligately eusocial corbiculate bees (stingless bees [Meliponini], bumble bees [Bombini] and honey bees [Apini]; Apidae), for example, numerous studies have shown that the exchange of food, symbionts, glandular secretions, and contact stimuli, between adults and immatures, or among adults, plays a key role in integrating these complex societies (e.g. Seeley, 1995; Page, 2013), and facilitates olfactory learning (Gil & De Marco, 2005).