Six new species of Microstigmus wasps (Hymenoptera: Sphecidae), with notes on their biology

Six new species of Microstigmus are described and illustrated. Nests and other aspects of their biology, when known, are also described. Microstigmus puncticeps sp. n. (northern Brazil and Peru) and M. xanthosceles sp. n. (Central America and western Colombia) belong to two distinct groups not closely related to previously described species. Microstigmus cooperi sp. n. and M. crucifex sp. n. (both from northern Brazil and Colombia) represent basal lineages within the large group including M. brasiliensis, M. theridii, M. lobifex, etc. Microstigmus flavus sp. n. (southeastern Brazil) is closely related to M. lobifex. Microstigmus simplex sp. n. (northern Brazil) is a basal lineage within the group containing M. guianensis and M. arlei. Reuse of nests of M. nigrophthalmus by M. flavus sp. n. and of M. crucifex sp. n. by a species of the M. theridii complex is reported for the first time for Microstigmus.