Trophallaxis refers to the direct transfer of food or fluids from one individual to another. It is especially common among the social insects such as bees, wasps, ants, and termites. In many species, including bees, trophallaxis is an important part of colony communication.
For example, workers who have licked the queen pass on some of the queenly essence to other bees during the exchange of food. Not only does this inform the colony that the queen is alive and well, but it also suppresses the development of ovaries in worker bees.
Bees also use trophallaxis to distribute information about new nectar sources or about feeding conditions inside the brood nest. It is also used to keep “heater bees” supplied with energy as they warm the nest. Unfortunately, trophallaxis can also aid in the spread of disease throughout a colony, especially when pathogenic organisms reside inside the honey bee gut.
check out my photos of bees doing trophallaxis on http://bees.msu.edu/2012/02/the-amorous-aussie-bees/.