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Sensory and cognitive adaptations to social living in insect societies

A key question in evolutionary biology is to explain the causes and consequences of the so-called “major transitions in evolution,” which resulted in the progressive evolution of cells, organisms, and animal societies (1⇓–3). Several studies, for example, have now aimed to determine which suite of adaptive changes occurred following the evolution of sociality in insects (4). In this context, a long-standing hypothesis is that the evolution of the spectacular sociality seen in insects, such as ants, bees, or wasps, should have gone hand in hand with the evolution of more complex chemical communication systems, to allow them to coordinate their complex social behavior (5). Indeed, whereas solitary insects are known to use pheromone signals mainly in the context of mate attraction and species-recognition, social insects use chemical signals in a wide variety of contexts: to communicate their caste or reproductive status, recognize nestmates from invaders, mark the way to food sources, or alarm nestmates about imminent danger (5). Well-controlled studies of the change in investment in chemical communication systems in highly eusocial insects, such as ants, termites, or Corbiculate bees, however, have proven hard to conduct, because eusociality in these taxa evolved long ago in the Cretaceous (6) and closely related solitary species are no longer around (Fig. 1). In PNAS, Wittwer et al. (7) now provide an elegant solution to this problem. By studying Halictinae sweat bees—a group of primitively eusocial insects that evolved sociality more recently and on several occasions reverted back to a solitary lifestyle (8) (Fig. 1)—they succeed in making an accurate comparison of the investment in chemosensory systems made by social and derived, closely related, nonsocial species.



Fig. 1. 
Cladogram showing the independent origins and secondary losses of sociality in the Hymenoptera (after refs. 6 and 20⇓⇓⇓–24). For clarity, … 



[↵][1]1To whom correspondence should be addressed. Email: tom.wenseleers{at}kuleuven.be.

 [1]: #xref-corresp-1-1