Liquid exchange via stomodeal trophallaxis in the ponerine ant Diacamma sp. from Japan

Trophallaxis plays a major role in the sharing of food in colonies of many social insects, and two modes of this are known: stomodeal (oral) and proctodeal (abdominal) trophallaxis. In social Hymenoptera, only a small proportion of colony members perform the task of food collection, and oral trophallaxis is predominant in their social sharing of food. Typically, foragers distribute liquid food stored in their crop to nestmates via oral trophallaxis. Similar to bees, some ants (Formicidae) forage for liquid food from plant secretions (nectars) and insect exudates (honeydew). While regurgitation is common in ants, it has been documented in only two species of the Ponerinae. Here, we report the ability of Diacamma sp. from Japan to perform trophallaxis. After thirsty ants had been paired with ants provided with colored water, the abdomens of both groups of ants were dissected. The digestive organ was colored red in half of the receivers. In addition, we observed mouth-to-mouth interactions in the laboratory, not “social bucket” behavior (i.e., exchange of liquid held between mandibles). Our results suggest that Diacamma sp. can exchange liquid by true oral trophallaxis and shed new light on social organization via liquid exchange.