Ants are dominant elements of most terrestrial ecosystems. They have prominent roles in agricultural environments, controlling pests or being pests themselves. Ants in natural habitats comprise a major fraction of the total animal biomass and have important roles as predators, scavengers, and soil movers. Many ant species have hitchhiked into new surroundings with humans, becoming invasive species that can harm both agricultural and natural ecosystems. Ants are also renowned for their complex societies. Because of their overall importance to human interest and welfare, ants are the subjects of scientific research on a wide variety of subjects, including behavior, robotics, immunochemistry, neurobiology, development, community ecology, biology of invasive species, and sociobiology. Knowledge of the evolutionary relationships among ant species (the "ant tree of life") adds great value to ant study findings. Advances in DNA sequencing technology have dramatically accelerated the discovery of evolutionary relationships among plants and vertebrates. Such knowledge is currently incomplete for ants, hampering research progress. The Ants of the World project will provide a comprehensive tree of life and classification of ants. The results will also address basic questions about how life spreads and diversifies across the planet.<br/><br/>A powerful new approach for revealing evolutionary relationships among animals uses genome reduction techniques and high-throughput sequencing to obtain thousands of loci called "UltraConserved Elements" (UCEs). Evolutionary trees based on UCEs reliably uncover relationships at all time depths. The Ants of the World project will acquire UCE data for 4,500 ant specimens, increasing the portion of sequenced species to 96% of the 334 genera and about 45% of the 13,500 described species. Specimens will be selected to include nearly all major species groups from all terrestrial biomes. The result will be a comprehensive evolutionary tree of ants delineated to the smallest branch tips. The tree will inform a revision of all generic boundaries and deliver the long-sought goal of a stable generic classification. The tree will also be linked to geography, morphological characters, and climate data, enabling exploration of fundamental evolutionary and ecological processes. The Ants of the World project will also become a major component of Ant Course, a brief but intensive field training program in ant diversity and identification. The Ants of the World project will support three new Ant Courses, in Cameroon, Vietnam, and Australia. A novel component of these courses will be the addition of undergraduate training in science communication: each course will include an undergraduate trainee who will document activities in the field and hone their science communication skills.<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.