In this paper 12 new species of scolytid beetles of the tribe Micracini are described from the United States, Mexico and Honduras. Notes concerning the geographical distributions and the biologies of a few other Mexican species are also included. Unless stated otherwise, the specimens taken in Mexico were collected by the author while with the 1953 expedition of the Francis Huntington Snow Entomological Museum (University of Kansas, Lawrence). The new species represent the following genera: Micracisella (3), Thysanoes (2), Pseudothysanoes (3), Crytocleptes (3), and Stenoclyptus (1).