OF WASHINGTON, VOLUME XIII, 1911. 215 A CLASSIFICATION OF THE SUBORDER CHALASTOGASTRA OF THE HYMENOPTERA. BY S. A. ROHWER. That the morphological characters exhibited by the most useful organs were least important as exhibiting relationship, for the reason that such characters were most subject to varia-tion, ivhereas structures of less use and importance -were neces-sarily less subject to variation and hence more indicative of affinities. (Dr. T. N. Gill, 1901.) The name "Chalastogastra" is used, as the best one that has been proposed, and it has been in use for a number of years in Euiope. Many other names have been given to this group of insects, but most of them are based on their habits. The nomenclature of the thorax and anterior wing is that given by Snodgrass. 1 The nomenclature of the posterior wing is that used by Cresson. The first dorsal abdominal segment (basal plates of authors) is called the propodeum. The present paper does not deal with groups lower than tribes. Genera not known from specimens are not placed. All species known to the writer can easily be placed in the tribe to which they belong. It would be a great favor to the writer if other workers would place the genera, not placed and known to them, into the division to which they belong. / Suborder CHALASTOGASTRA. TABLE TO THE SUPERPAMILIES. Posterior margin of the pronotum straight or nearly so, being nearly the shortest distance between the anterior margins of the tegulae; mesonotum very short and never extending much beyond the anterior margins of the tegulaa; proepimeron wanting Megalodontoidea Posterior margin of the pronotum strongly curved; mesonotum longer and extending well beyond the anterior margins of the tegulae I 1. Metanotum concealed, but the metapostnotum is present and large; antennae inserted much below the lower margins of the eyes, and below the apparent clypeus; propodeum not divided; proepimeron wanting; an-terior wings with two cubital cells Oryssoidea Metanotum always present, although the metapostnotum is sometimes concealed; antennae inserted well above the clypeus; anterior wings with more than two cubital cells 2 1 The thorax of the Hymenoptera. Proc. U. S. Nat. Mus., vol. 39, no. 1774, pp. :!7-91, plates 1-16. 1910.