Evidence of a thoracic crop in workers, soldiers, and queens of Carebara perpusilla ants (Formicidae: Myrmicinae)

The ability to share and store food is paramount in group-living animals, allowing a finely tuned distribution of resources over time and individuals and an enhanced survival over periods of food scarcity. Ants have several ways to store food: one of them is their gastral crop, also known as a "social stomach." Nutrients in the crop can be regurgitated to nestmates through oral trophallaxis (mouth-to-mouth) or proceed to the midgut by opening the proventriculus, a valve connecting the crop to the midgut. However, some ants are also known to have a so-called "thoracic crop," an extension of the esophagus that allows for additional storage space. In this study, we provide the first evidence of a thoracic crop in the genus Carebara, in reproductive (queen) and sterile (soldier and worker) castes. We discuss how the ant body plan allowed for the evolution of a novel food storage structure in the mesothorax.