Ichneumon ambiguus Cresson, 1864:161, ♂. ♂, Pennsylvania (leg. E. T. Cresson); Heinrich, 1961Heinrich, G.H. 1961. Synopsis of Nearctic Ichneumoninae Stenopneusticae with particular reference to the northeastern region (Hymenoptera). Part I. Introduction, key to nearctic genera of Ichneumoninae Stenopneusticae, and synopsis of the Protichneumonini north of Mexico. The Canadian Entomologist 92 (Supplement 15):1-87.:25, Holotype ♂ (A.N.S.); Heinrich, 1977Heinrich, G.H. 1977. Ichneumoninae of Florida and neighboring states (Hymenoptera: Ichneumonidae, subfamily Ichneumoninae). Arthropods of Florida and neighboring land areas 9:1-350.:18, Holotype ♂ (ANS, no. 1436). - Heinrich, 1961Heinrich, G.H. 1961. Synopsis of Nearctic Ichneumoninae Stenopneusticae with particular reference to the northeastern region (Hymenoptera). Part I. Introduction, key to nearctic genera of Ichneumoninae Stenopneusticae, and synopsis of the Protichneumonini north of Mexico. The Canadian Entomologist 92 (Supplement 15):1-87.:25 ( listed as synonym of Protichneumon grandis grandis (Brullé, 1846)); Krombein et al., 1979Krombein, K.V., P.D. Hurd, D.R. Smith & B.D. Burks 1979. Catalog of Hymenoptera in America North of Mexico. Volume 1. Symphyta and Apocrita (Parasitica). Smithsonian Institution Press, Washington D.C. 1-1198.:534 ( listed as synonym of Protichneumon grandis (Brullé, 1846)). - As Protichneumon ambiguus: - Heinrich, 1977Heinrich, G.H. 1977. Ichneumoninae of Florida and neighboring states (Hymenoptera: Ichneumonidae, subfamily Ichneumoninae). Arthropods of Florida and neighboring land areas 9:1-350. (distribution).