Queen influence on the shift from trophic to reproductive eggs laid by workers of the ponerine ant Pachycondyla apicalis

Abstract

A single queen reproduces in the colonies of the ponerine ant Pachycondyla apicalis (87 ± 75 workers, n = 85; Fresneau, 1994). Although the castes are only weakly dimorphic, the workers cannot mate and are restricted to producing males. In five queenright colonies, workers laid trophic eggs only and had low levels of ovarian activity. Trophic eggs differ morphologically from reproductive eggs, and are immediately offered to the queen who eats them. In one orphaned colony, a proportion of workers laid reproductive eggs only. Another colony was divided with a double mesh, and after 11 days, workers lacking direct contact with the queen also began to lay reproductive eggs. The age of almost all workers was known in this colony, and their ovarian activity was correlated with age both in the presence and absence of the queen. Our data suggest that the putative queen pheromone is transmitted by close-range contact. The queen walks regularly around the nest, which could be a means of transmitting her signal. Importantly, workers in another two queenright colonies interacted aggressively and laid reproductive eggs, revealing the occasional existence of direct competition for male production between the castes.