Queen transport during ant colony emigration: a group-level adaptive behavior

Ant colonies emigrate frequently from one nest site to another. Emigrations , however, are dangerous, particularly for colonies with a single queen. Th e queen is a "vital organ" of the colony, and emigrations expose her to gra ve peril. The optimal strategy for a monogynous ant colony, therefore, shou ld be that the queen moves during the middle of the emigration so that she is transferred swiftly from the protection of half of the colony in the old nest to the protection of the other half colony in the new nest. In the an t Leptothorax albipennis, the queen is carried during colony emigration. We tested the null hypothesis that the queen has a random position in the seq uence of transport events during an emigration. The result of 32 emigration s demonstrated, for the first time, that the transport serial number of the queen [calculated relative to the total number of all transport events (i. e., of broad and adult ants together), brood transport events, or adult ant transport events] is not random and furthermore occurs in the middle of th e transport sequence. This result represents a colony strategy because we f ound that the relative transport serial number of the queen was related nei ther to emigration distance nor to colony size. Transporting queens in the middle of emigrations is a strategy probably favored by selection and is an aspect of colonies behaving as group-level adaptive units.