The Stephanidae (Hymenoptera) of Mexico, with description of six new species and a key to western Foenatopus Smith

The Mexican genera and species of Stephanidae, and the western species of Foenatopus Smith are revised. Twelve species are recognized, two in Foenatopus and ten in Megischus Brullé, all but one occurring in Mexico. Six new species of Megischus are described, M. anaxeus sp. n., M. celaenocephalus sp. n., M. jaliscoensis sp. n., M. melanogladius sp. n., M. mexicanus sp. n., and M. peninsularis sp. n. One genus (Foenatopus Smith) and four species are registered for the first time in Mexico, F. annulipes Kieffer, M. arizonicus Townes, M. bicolor (Westwood), and M. niger Smith. Many new distribution records in Mexico and intensive new morphological variation are registered, illustrated and discussed for M. texanus Townes. Much new morphological variation is reported and illustrated for M. arizonicus. The male of F. aurantiiceps Brues is reported for the first time. Mexico is identified as an area of overlapping distribution between the essentially North American M. bicolor and the typically Central American M. niger; intermediate forms between these two species are described, and new diagnostic features are proposed for their identification. Some of the treated species are proposed as possibly highly endemic, occurring only in particular regions in the country, namely M. peninsularis, restricted to Baja California, and M. celaenocephalus, restricted to central Mexico. Some of the morphological variation observed for F. aurantiiceps is tentatively linked to specimens occurring in the south vs. north of the Amazon river, and to localities of high vs. low altitude. General stephanid morphology is illustrated, its correspondent terminology updated, and a key is provided for recognition of all treated genera and species. Full description is provided for each new taxon, and photographic illustrations are provided for all valid taxa. Extensive biometric data, and RGB formulas for color variation are provided for nearly all treated species.