298 PROC. ENT. SOC. WASH., VOL. 71, NO. 3, SEPTEMBER, 1969 Leibowitz, J. 1943. A new source of Trehalose. Nature 152:414. Mackauer, M. and P. Stary. 1967. Hym. Ichneumonoidea, World Aphidiidae. In Delucchi V. and Remaudiere (Editors), Index of Entomophagous Insects. Le Francois, Paris, 195 pp. Stary, P. 1966. Aphid parasites of Czechoslovakia. Academia, Prague and Dr. W. Junk Publ., The Hague, 242 pp. . 1966. Aphid parasites ( Hymenoptera: Aphidiidae) and their re-lationship to aphid attending ants, with respect to biological control. Ins. Sociaux 13(3): 185-202. 1968. Geographic distribution and faunistic complexes of parasites (Hymenoptera: Aphidiidae) in relation to biological control of aphids (Homop-tera: Aphidoidea). Acta Univ. CaroHnae, Biologica 1967:23-89. THE NORTH AMERICAN SPECIES OF ARTHROLYTUS THOMSON ( Hymenoptera : Pteromalidae ) B. D. Burks, Systematic Entomology Laboratory, U. S. Department of Agriculture^ ABSTRACT — A history of the genus Arthrolytiis Thomson in North America is given, with redescription of A. fasciatus ( Provancher), occurring in northeastern states, and description of A. muesebecki, n. sp., from California, reared from cynipid galls on oak. Arthrolijtus Thomson has had a curious history in North America. It was a quite commonly used chalcidoid generic name in the Nearctic Hterature for about 40 years, but passed out of use, and very recently has again been used. Several European species of Arthrolytus had been known since 1878, but no Nearctic species were described until 1893. In that year Ashmead recognized what he took to be this genus from Ohio and described Arthrolytus apatelae. In 1894 he characterized another spe-cies, A. pimplae, from Virginia. Also in 1894 Ashmead transferred Cleonymus clisiocampae Fitch, described from New York state, to Arthrolytus. Thus, in the 1890's Arthrolytus had 3 Nearctic species, the names of which appeared in numerous economic reports, faunal lists, and catalogues, because they were often identified as primary or secondary parasites of common lepidopterous hosts. However, these names gradually disappeared from the literature. In 1897 Howard synonymized Arthrolytus clisiocampae under the ^ Mail address: c/o U. S. National Museum, Washington, D. C. 20560.