Ecology and Behavior of the primitive cryptobiotic ant Prionopelta amabilis (Hymenoptera: Formicidae)

We report here the first detailed account of a member of Prionopelta, a pantropical genus possessing the smallest workers in the primitive ant tribe Amblyoponini. 1. Colonies of P. amabilis were found nesting in small rotting logs and tree branches on the floor of primary rain forest in Costa Rica. Two that were more carefully excavated possessed a single dealate queen and a worker population unusually large for Amblyoponini. One of the latter colonies, which was in the process of eclosing alate queens (during late March), contained over 700 workers. 2. P. amabilis workers prey preferentially on campodeid diplurans, although they also accept (less readily) a limited variety of other small arthropods. The prey are given directly to the larger larvae. The queen is fed trophic eggs which we infer to have been laid by the workers. 3. A moderately well-marked temporal division of labor occurs, thus distinguishing P. amabilis from Amblyopone pallipes, the only other amblyoponine hitherto studied in this regard. Younger workers attend the brood and queen, forming a retinue around the latter individual. Older workers are more active in foraging. As expected, the ovaries are better developed in workers associated with the queen than in foragers. 4. Emigration to nest sites is conducted individually, with the workers carrying brood but not other adult nestmates. A foot-dragging behavior, possibly associated with trail-laying, is described. Alarm pheromones are apparently absent. 5. A unique "wall-papering" behavior was also discovered: the workers line the pupal chambers with fragments of discarded pupal cocoons, rendering these spaces drier and hence presumably more suitable for pupal occupation.