An unusual new species of Canthidium (Coleoptera: Scarabaeidae: Scarabaeinae) from Oaxaca, Mexico

In this paper we describe Canthidium quercetorum new species (Coleoptera: Scarabaeidae: Scarabaeinae), a species that inhabits dry oak forest in the Mexican state of Oaxaca, between 2100 and 2300 m above sea level. Photographs and an illustration of the habitus and a distribution map are provided. The unusual distribution and ecology of this species are discussed. An updated key for the genus in Mexico and the United States of America is also presented. The total number of Canthidium Erichson in Mexico has increased significantly since Kohlmann (2003) listed six species in the country. Kohlmann and Solís (2006a, 2006b) described eight new species from Mexico bringing the total up to 14. This new species brings the total number of Mexican Canthidium species to 15. As a comparison, Costa Rica has 25 species and Panama has 19 species of Canthidium (Solís & Kohlmann 2004, 2012). Harold (1867) made the very pertinent observation that Canthidium substitutes Onthophagus Latreille ecologically in South America. Although this is partially true in Mexico, where many Canthidium species are found in humid tropical conditions along the Gulf of Mexico coast, Canthidium has been able to colonize environments in the mountains, like cloud forests and even dry tropical forest. However, the new species we are describing occurs in typical Onthophagusrelated environments, such as the dry oak forest within the mountains of the Oaxaca Valley. Measurements were made to the nearest 0.1 mm using an ocular micrometer with a Stemi DV4 stereoscope. The holotype, allotype, and paratypes of C. quercetorum are deposited in the Colección Entomológica, Instituto de Ecología Xalapa, Mexico (IEXA). Paratypes in the Muséum National d'Histoire Naturelle, Paris, France (MNHN); the Canadian Museum of Nature, Ottawa, Ontario, Canada (CMNC); and the Coleção de Entomologia of the Universidade Federal de Mato Grosso, Cuiabá (CEMT).