GENUS STIZUS LATREILLE IN NORTH AMERICA (HYMENOPTERA: NYSSONINAE) J. WILLIAM STUBBLEFIELD' Abstract. The five North American species of Stizus Latreille are reviewed. Stizus aztecus is described, and nev^ descriptions are provided for the other four species: S. brevipennis Walsh, S. texanus Cresson, S. occi-dentalis Parker, and S. iridis Dow. A key to these species is provided, and the distribution of each species is documented. The North American species belong to two well-defined species-groups, the brevipennis group and the ruficornis group, and the characters defining these two groups are discussed. The ethology of Stizus is reviewed, and a worldwide list of the published prey records is presented. INTRODUCTION The species belonging to the genus Sti-zus are large, often brightly colored, ground-nesting wasps that provision their nests with Orthoptera. With more than 120 species now recognized, Stizus is one of the largest genera in the Nyssoninae with only the cosmopolitan genera Bembecinus and Bembix containing more species. Sti-zus is widespread in Africa, Eurasia, and North America but is absent from Austra-lia and the Americas south of Mexico. The vast majority of species occur in the Old World, and only five species are known from North America: S. brevipennis Walsh, S. texanus Cresson, S. aztecus new species, S. occidentalis Parker, and S. iri-dis Dow. The North American species fall into two well-defined species groups, the brevipennis group which is restricted to North America and the ruficornis group which is well developed in Africa and Eurasia. Two other species groups are also recognized but do not occur in North America, the very large fasciatus group with numerous species in the Old World and the monotypic scolaeformis group of Africa. ' Museum of Comparative Zoology, Harvard Uni-versity, Cambridge, Massachusetts 02138. Present address: Department of Biology, University of Utah, Salt Lake Citv, Utah 84112. The present work provides a review of what is now known about the North American species of Stizus, including their taxonomy, distribution, and ethology. A new species, S. aztecus, is described, and each of the previously known species is redescribed in order to remedy certain deficiencies in earlier descriptions and to facilitate comparisons between species. The male genitalia and sternum VIII of each species are illustrated with SEM pho-tographs; these structures differ markedly between species and provide a reliable ba-sis for identification. The characters serv-ing to distinguish the brevipennis and ruficornis groups are discussed, and a key to the North American species is provid-ed. It is unlikely that any new species will be discovered in North America, but much remains to be learned about the biology of Stizus. Prey records, for example, exist for only two of the five North American species and only eleven of the more than 100 species occurring in the Old World. Even less is known about the nesting be-havior of Stizus; only the East Asian S. pulcherrimus has been studied in much detail (Tsuneki, 1965). A worldwide list of prey records for Stizus is provided here, and Evans (1966) may be consulted for a general review of Stizus ethology. A sizeable, though rather scattered, lit-erature devoted to Stizus has developed since the classical monograph of Hand-Bull. Mus. Comp. Zool., 150(7): 397-428, September, 1984 397
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