Ant cuticle microsculpturing: diversity, classification, and evolution

Taxonomists have created over 150 unique terms to describe microsculpturing patterns in ants and other insects, but the evolution and function of these patterns has remained a mystery. To develop a better understanding of the evolution and function of cuticle microsculpturing, we developed a simplified classification system consisting of five broad categories: smooth, reticulate, striate, punctate, and tuberous. We used this system to classify microsculpturing patterns of 11,739 species and subspecies of ants, which we then mapped onto the current genus-level ant phylogeny. We found strong support that smooth was the ancestral state of microsculpturing in ants. All other microsculpturing patterns evolved independently multiple times, and there have been numerous instances of reversions and reacquisitions of similar pat-terns. In general, most ants were smooth, and rough textures tended to be associated with subfamilies whose members have a thicker cuticle, particularly Myrmicinae and Ectatomminae. Tuberous was the least common microsculpturing pattern and was largely confined to fungus-gardening ants in the tribe Attini. The function of cuticle microsculpturing is still unknown, but it may play a role in providing structural support, abrasion reduction, desiccation resistance, communication, and influence insect-microbe interactions. We review these proposed functions and discuss how ant microsculpturing may inspire future applications in bio-inspired design.