Food storage and morphological divergence between worker and soldier castes in a subterranean myrmicine ant, Carebara perpusilla

Abstract

ABSTRACT Food reserves and trophallaxis help insect colonies regulate brood development and survive starvation events. Unlike wasps and bees, ants do not store food in external structures within the nest. Therefore, an ant colony’s ability to store food is greatly enhanced by the development of highly dimorphic workers and soldiers that are able to store food within their bodies. Carebara perpusilla (subfamily Myrmicinae, Emery, 1895) has a subterranean lifestyle and three castes: workers, soldiers with a proportionally larger head and gaster, and large winged queens. Workers are minute (1.5 mm long) and can hunt solitarily on tiny arthropods such as springtails and scavenge in groups on dead insects of various sizes. Rather than carrying big corpses to the nest, they bury it with soil and only retrieve haemolymph and small solid pieces. Moreover, some soldiers and virgin queens have a distended gaster and function as repletes. Food dyes revealed the storage of fat in the crop. Using dissections supplemented by micro-CT visualisation, we compared the crop of workers, soldiers and virgin queens and its capacity for considerable expansion. We discuss the morphological specialisation of repletes in ants that do not collect honeydew. Natural history data of more subterranean ants are needed to understand the adaptive context of foraging and other behaviours.