J. HYM. RES. Vol. 14(1), 2005, pp. 22-65 A Review of North American Species of Microdontomerus Crawford (Torymidae: Hymenoptera) E. E. Grissell Systematic Entomology Laboratory, PSI, Agricultural Research Service, U. S. Department of Agriculture, c/o National Museum of Natural History, Smithsonian Institution, Washington, DC 20560-0168, USA; email: [email protected] Abstract. — Four species of Microdontomerus Crawford have been recognized in the New World: anthidii (Ashmead), anthonomi (Crawford), bicoloripes (Crawford), and fumipennis Crawford. In this paper the genus is revised and the following new species are described: apianus, braconivorus, buprestae, ciscada, darwini, eboreus, enigma, gordhi, hemileucae, mysticus, parkcri, rictus, seats, westcotti, and zoyphius, making a total of 19 described New World species. Keys and illustrations are given to distinguish all species, and host and distribution data are summarized. The new species include parasitoids of range caterpillar eggs (possibly as hyperparasitoids); geometrid larvae; tachinid and braconid parasitoids of Lepidoptera; several burprestid crown borers; a cer-ambycid stem borer; root and stem weevils; and several solitary bees. The genus Microdontomerus Crawford is known from nine species of which four are North American: anthidii (Ashmead), anthonomi (Crawford), bicoloripes (Craw-ford), fumipennis Crawford; four are Pale-arctic: albipes (Giraud), annulata (Spinola), gallicolus Zerova and Seryogina, ovivorus (Steffan); and one is Afrotropical: senega-lensis (Risbec) (Grissell 1995, Zerova and Seryogina 1999, Noyes 2001). No species are yet known from the Australian or Ori-ental Regions, or from Central or South America. Because no keys or reviews have been published for the relatively few North American species of Microdontome-rus, the purpose of this paper is to docu-ment the occurrence of 15 previously un-described species for the area and to pro-vide a key and illustrations to identify them. This paper essentially covers all known information for New World spe-cies of Microdontomerus, most of which ap-pear to be primarily western North Amer-ican. Most species of Microdontomerus appear to have a narrow host range, but the over-all array of insects attacked by members of the genus is conversely broad. For ex-ample, several species are parasitoids of various life stages of Lepidoptera; several attack larvae of bees and one attacks cy-nipids; one is an egg parasitoid of bupres-tids; and one has been reared from mantid egg cases. Several species have broad host ranges, and are hyperparasitoids through either a lepidopterous or coleopterous host. In the former case, the wasp also at-tacks ichneumonid parasitoids (Peigler 1985), and in the latter the wasp attacks tephritids that live in the same microhab-itat (Turner et al. 1990). Hosts for new spe-cies described in this paper include range caterpillar eggs (possibly as a hyperpar-asitoid); geometrid larvae; tachinid and braconid parasitoids of Lepidoptera; sev-eral burprestid crown borers; a ceramby-cid stem borer; root and stem weevils; and several solitary bees. Apart from host data, little biological information is avail-able for New World species, and what lit-tle is available is summarized under in-dividual species below.