These adaptations partly explain why ants have been so extraordinarily successful in nature, and underscore the importance of carefully analyzing an organism’s form to fully understand its biology. show that female ants invest in the relative size of the different segments of the thorax in a way that reflects their behavior as adults. Taken together, the results of Keller et al.
show that we can use the shape of the queen’s thorax to help predict this behavior. As such, for those ant species where very little is known about how new colonies are founded, Keller et al. In species where queens hunt to feed the new colony, the wing and neck muscles are more balanced in size. In species where queens convert their own wing muscles into the food for the first generation of workers, the wing muscles are much enlarged and the neck segment is extremely reduced. also identified two distinct types of queens and went on to show that these two shapes evolved in association with the two types of strategy that lone queens use to found new colonies. The front end of the worker thorax is greatly enlarged and is filled by strong neck muscles that power the head and its jaws, and allow workers to hunt and carry prey many times their own weight. have examined the shape of the thorax in many species of ants and found that workers are not just smaller wingless versions of queens: rather, the architecture of their thorax is unique among species of flying insects. Like all insects, an ant’s body is divided into three parts: the head, the thorax (to which the legs and wings are attached), and the abdomen. However, most studies have focused on the presence or absence of wings and have overlooked the interactions between morphology and the actions performed on the ground. This marked morphological divergence, unique to ants, has fascinated researchers for more than a century. Workers are smaller and lack wings, and they devote themselves to building the nest, feeding the young larvae and protecting the colony. Queens are responsible for reproduction, and are larger and have wings, which allow them to fly and establish a new colony away from where they were born. Queens and workers within an ant colony have a similar set of genes, but they have dramatically different morphologies and very different roles within the colony. The interplay between morphology and behavior is particularly interesting in social insects such as ants. A change in morphology can make new behaviors possible, which can then expose the animal to new environments and selective pressures that, in turn, can lead to further changes in morphology. These specialized features result from the interplay between morphology and behavior during evolution. A grasshopper’s long legs, for example, are well suited to hopping, whilst the streamlined body of a dolphin helps swimming through water. The size and shape of an animal, known as its morphology, often reflect the actions it can perform. Versatility of head movements allows for better manipulation of food and objects, which arguably contributed to the ants’ ecological and evolutionary success. Our results reveal that ants invest in the relative size of thorax segments according to their tasks. Solitary founding queens that hunt have a more worker-like thorax.
We also identified two distinct types of queens and showed repeated evolutionary associations with strategies of colony foundation. We uncovered unique skeletomuscular modifications in workers that presumably increase power and flexibility of head–thorax articulation, emphasizing that workers are not simply wingless versions of queens. We analyzed thorax morphology of queens and workers in species from 21 of the 25 ant subfamilies.
Unique to ants is a marked divergence between winged queens and wingless workers, but morphological specializations for behaviors on the ground have been overlooked. The concerted evolution of morphological and behavioral specializations has compelling examples in ant castes.