The known 19 North American species of Rhyssomatus (Curculionidae: Molytinae: Cleogonini), a New World weevil genus initially described by Schoenherr in 1837, have not been treated since Casey in 1895 and require revision. The monophyly, internal phylogeny, species-level diversity, and reliable, updated species identification resources for this widespread weevil lineage remain underexplored or unavailable. Rhyssomatus are associated with many plants in the families Asclepiadaceae, Asteraceae, Convolvulaceae, Fabaceae, Malvaceae, Papilionaceae, among others. Rhyssomatus niggerrimus in Mexico and R. subtilis in Argentina are known agricultural pests. Adult feeding and ovipositing behavior as well as larval feeding habits pose a significant threat to the cultivation of agricultural soy (Glycine max (L.) Merrill) at all stages of the crop. The economic impact and lack of reliable taxonomic access to these weevils provides a practical imperative to further study Rhyssomatus. The specific aim of this project is to provide a key to the 12 species of Rhyssomatus known to occur in the state of Arizona, U.S. In addition to the previously hypothesized species groups of this genus, defined by the morphological characters of male and female genitalia, I here present a new diagnostic key to the Rhyssomatus speciesof Arizona.
