PROC. ENTOMOL. SOC. WASH. 88(3), 1986, pp. 542-549 OBSERVATIONS ON THE BIOLOGY OF TWO SPECIES OF ORASEMA (HYMENOPTERA: EUCHARITIDAE) 1 J. B. Johnson, T. D. Miller, J. M. Heraty, and F. W. Merickel (JBJ, TDM, FWM) Department of Plant, Soil and Entomological Sciences, University of Idaho, Moscow, Idaho 83843; (JMH) Department of Environmental Biology, University of Guelph, Guelph, Ontario NIG 2W1, Canada. Abstract. — Brief descriptions of life history are given for Orasema coloradensis and Orasema viridis from Idaho and Arizona, respectively. O. coloradensis was reared from nests of Formica subnitens and both species of Orasema were found in association with thrips. Descriptions of the first-instar larvae are made and the larvae compared to other Eucharitidae. Members of the genus Orasema Cameron, like other members of the family Eucharitidae (Hymenoptera: Chalcidoidea), are parasitic upon ant pupae. Adult females lay their eggs into plant tissue, away from the host, and the active first-instar larvae seek adult ant hosts for transport back to the nest (Clausen, 1940). Wheeler (1907) published the first account of the in-nest habits and gave host records for three species of Orasema. He provided a sketch of the planidium of O. viridis Ashmead, a parasite of Pheidole kingi instabilis (Emery), and illustrated the later larval instars in detail. Wheeler and Wheeler (1937) supplied further information on the larval development of two other species, Orasema sixaolae Wheeler and Wheeler and Orasema costaricensis Wheeler and Wheeler, which parasitize the ants Solenopsis tenuis Mayr and Pheidole flavens Roger, respec-tively. The out-of-nest habits of Orasema sp. (near aenea Gahan) were first described by Parker (1942) in Argentina. He wrote that adults deposited their eggs in ser-pentine rows into leaves of a Muehlenbeckia (Polygonaceae) and provided de-scriptions and figures for the planidium and egg (one egg per puncture) as well as details on the oviposition behavior. Das (1963) supplied similar information for Orasema assectator Kerrich, which is parasitic on a species of Pheidole in India. Again, eggs were deposited in serpentine rows on tea leaves, and although not stated explicitly, Das implies that a single egg is deposited per oviposition punc-ture. Orasema costaricensis was reported to oviposit into young banana fruits (Kerrich, 1963). Since the host ants of O. assectator do not forage on the tea bushes, Das (1963) mentions a possible role for Empoasca flavescens (F.) (tea leafhopper) or Scir-tothrips dorsalis Hood (tea thrips) as intermediate carriers of the planidia. Other 1 Published with the approval of the director of the Idaho Agricultural Experiment Station as Research Paper No. 8676.