OF WASHINGTON, VOLUME XII, I'Hll. 99 The following paper was accepted for publication: DESCRIPTIONS OF NEW PSENID WASPS FROM THE UNITED STATES. [Hymenoptera; Psenidae.] BY S. A. ROHWER. If in general Dr. Ashmead's classification of the Sphecoidea is to be followed, and the genera Pscn and Pemephredon, as understood by Latreille (Free. car. gener Insect, 1796) are to be united in the same family, the name should be Psenidae and not Petnphredonidse, as Dr. Ashmead has it, because Psen was described on page 122 and Pemphredon on page 128. According to many authors these two genera have been made the types of two distinct families, and by some have been widely separated. Such wide separation has been due to the fact that some authors have considered cubital venation to be of the greatest importance. This view of the great importance of venation is gradually being given up and students are looking to the body itself for the principal characters and treating the appendages secondly. Such a method of study will no doubt bring about a more natural classification. It is, however, to be expected that in many-perhaps a majority cases the characters of the appendages will correlate so well with the body characters that a satisfac-tory arrangement could be built up on characters easily seen on the appendages. But until such relationships have been fully established the body should be carefully studied. Whatever may have been the origin of the Pseninae and Pemphredonina^, there can be but little doubt that at the present they are closely enough related to belong to the same family. An examination of the type genera of the two sub-families will show that the thorax and abdomen are much the same, but that the head of Pemphredon is larger, and has the antennae inserted close to the clypeus. In the wings Pem-phredon differs in the loss of the first transverse cubitus. All these differences do not hold throughout the two subfamilies, however, for in Ammoplanus, Diodontits, and in some species of Passalcvcns the head is smaller, and has more the shape of species found in Pseninse. The position of the antenna 1 is as in Pemphredon, and at least one transverse cubitus is want-ing. The difference in venation between the types of the two subfamilies is not as great as the difference between Stignius and Pemphredon, both belonging to the Pemphredoninae.