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. 



