PROC. BIOL. SOC. WASH. 91(3), 1978, pp. 590-635 A REVISION OF THE NEW WORLD SPECIES OF HEDYCHRIDIUM (HYMENOPTERA, CHRYSIDIDAE) R. M. Bohart and L. S. Kimsey Abstract. — Hedychridium with its 36 New World species, 24 of which are described as new, is reviewed. The genus is in the subfamily Elampinae, and is the only one with a single median claw tooth. Most of the species are found in western United States and particularly the southwest. Biology of only one New World species is known, but Old World forms are parasitoids on sphecids and bees. Characters of special value are discussed, especially male genitalia, which are figured. Six species groups are defined and a key to species is presented. New species are antennatum Kimsey, argenteum Kimsey, arietinum Bohart, azurellum Bohart, bilobatum Bohart, centrale Bohart, cornutum Bohart, coruscum Bohart, crassum Bohart, crebrum Kim-sey, frontis Kimsey, frugale Bohart, gemmatum Kimsey, incisum Bohart, leucostigma Bohart, lividum Bohart, maricopae Bohart, menkei Bohart, milleri Kimsey, mirabile Kimsey, nevadae Kimsey, olene Kimsey, paulum Bohart, politum Bohart, purum Kimsey, rasile Bohart. A lectotype is estab-lished for Hedychrum discoidale Buysson. The genus Hedychridium Abeille de Perrin, 1878, includes about 150 named species of cuckoo wasps, occurring mostly in the Holarctic Region. Many of the species are small, often less than 4 mm long. The New World forms are commonly blue to purple, but a significant number from desert areas of southwestern United States exhibit metallic hues of copper, gold and red; thus rivalling the brilliant species of the Palearctic. The genus falls in the subfamily Elampinae, characterized by having no female sting, abdominal venter mostly flat to concave, 3 well defined and exposed abdominal segments, tarsal claw with one or more subsidiary teeth, no transverse frontal carina, radial sector with its sclerotized basal part (RS stub) not extending apicad much beyond stigma, and outer veins of discoidal cell not fully sclerotized. Among the elampine genera, Hedych-ridium can be separated by a combination of characters: claw with a me-dian tooth (Fig. 32), median cell of forewing setose, RS stub extending apicad at least as far as stigma, tergum III margin rounded or slightly in-dented apically ( the closely related Ethiopian genus, Acrotoma, has a pair of apical teeth). Geographic distribution. — Of the approximately 150 described species of Hedychridium, 32 are Nearctic (including the 24 described herein), 4 are neotropical, a few are Ethiopian or Oriental, and the rest are Palearctic. Considering the number of odd specimens which we were unable to readily
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