The anatomy of the adult of Monodontomerus dentipes Boh., a chalcid parasite of sawfly cocoons in Europe and America, is described. An attempt is made to homologize the structures of this highly modified insect with those known in more generalized insects, in the hope of clarifying some questions of chalcid morphology which has been generally neglected by entomologists. The nomenclature employed is of a kind generally acceptable to students of morphology, an effort being made to eliminate the use of terms specific to a limited group of insects. The anatomy of Monodontomerus is not widely different from that of phytophagous chalcids described by other authors.