The 19th century English poet William Blake might’ve been onto something when he considered an entire world in a grain of sand. But he probably didn’t consider tiny “monsters,” smaller than rice grains. Researchers have discovered 33 new species of ants in Central America and the Caribbean. The insects have broad, shieldlike faces and mandibles bristling with sharp teeth, such as Eurhopalothrix procera (pictured above), and none are longer than 2.5 millimeters. Their grim visages inspired names based on Maya demons Hunhau, Zipacna, and others. Many had been previously lumped in with other species of the Eurhopalothrix and Octostruma genera. The ants were found mostly in the plant debris of Central and South American mountain forests. Researchers had to sift through 100 square-meters of forest floor for every four or five of the rare specimens, then use a high-power microscope and micrometer measuring tool to note variations in size, the shape of their mandibles, and patterns of hair on their exoskeletons—all defining characteristics of individual species. Frightening work.