Two new species of Ormyrus Westwood (Hymenoptera: Ormyridae) from Cynipidae (Hymenoptera) galls on Silphium L. (Asteraceae: Heliantheae)

Two new species of Ormyrus Westwood, 1832 (Hymenoptera: Chalcidoidea: Ormyridae) are described: Ormyrus myrae Nastasi, Alcorn, & Davis sp. nov. and Ormyrus bellbowl Nastasi, Alcorn, & Davis sp. nov. Species of Ormyrus are parasitoids in insect galls, especially those induced by Cynipidae (Hymenoptera: Cynipoidea), and the new species are parasitoids in galls induced by Antistrophus Walsh, 1869 (Cynipidae: Aulacideini) on rosinweeds of the genus Silphium L. (Asteraceae: Heliantheae). Ormyrus bellbowl is a parasitoid of Antistrophus meganae Tooker & Hanks, 2004 in stems of S. terebinthinaceum Jacq., as well as other species of Antistrophus inducing inconspicuous galls in stems of S. laciniatum L. Ormyrus myrae is a parasitoid of Antistrophus laciniatus Gillette, 1891 on S. laciniatum and S. terebinthinaceum; the latter represents a new association of A. laciniatus with S. terebinthinaceum. Previous records of O. labotus Walker, 1843 in association with Antistrophus species are suggested as the results of misidentifications.