38 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.39. 



The study of the Hymenopteran thorax here presented is a con- 

 tribution from the United States Bureau of Entomology, prepared 

 under the direction of its chief, Dr. L. O. Howard. The work by 

 the writer has been in the nature of a collaboration with Mr. J. C. 

 Crawford of the United States National Museum and with Mr. H. L. 

 Viereck and Mr. S. A. Rohwer of the bureau, who, as specialists in 

 various groups of the Hymenoptera, have furnished not only the 

 identified specimens from which the dissections and drawings were 

 made, but also the taxinomic plan followed in treating the various 

 species. 



The most irreconcilable subject of contention between systematists 

 and morphologists is in the field of terminology. The morphologists, 

 of course, insist that the same anatomical parts should be given the 

 same names in all the orders. The systematists, on the other hand, 

 inheriting from their forerunners in taxinomy a difl^erent set of terms 

 in each order, hold that these names should be retained for the sake 

 of convenience, since every new student has to learn them anyway. 

 They think it well enough to let such names remain as they are 

 with the understanding that they are merely handles to the difi'erent 

 parts used in description and that they are not supposed to have 

 any morphological significance. Furthermore, the moi-phologists 

 often make up such cumbrous terms, that, however significant from 

 an anatomical standpoint, they are far too unwieldy for using as 

 the names of organs or parts in specific descriptions. Hence, per- 

 haps complete uniformity will never exist in entomological nomen- 

 clature. In the preparation of the present paper, however, no such 

 conflict has arisen, and this for two reasons: First, the lateral and 

 ventral parts of the Hymenopteran thorax have been so little used 

 in specific descriptions that no system of names has yet been given 

 to them; and secondly, the names commonly applied to the back 

 plates are in some cases so glaringly misplaced that even systematists 

 themselves are glad to have their nomenclature revised. 



At first sight the thorax of most of the Hymenoptera appears 

 very different from that of all other insects. Not only does it seem 

 impossible to make out the ordinary parts of each segment, but the 

 limits of the segments themselves are obscure. For a true solution 

 of the subject the student must begin with a study of the Tenthre- 

 dinoidea and Siricoidea and compare their structure with that of the 

 more generalized orders of insects. While some entomologists have 

 separated these two groups as a distinct order from the rest of the 

 Hymenoptera, there can be no doubt that in their thoracic charac- 

 ters they are truly Hymenopteran. Yet, on the other hand, their 

 thorax is so generalized that one can not possibly mistake its mor- 

 phology in a comparison with the thorax of a grasshopper or stonefly. 

 Hence, if the Phytophaga, so called, had become extinct, the Hymen- 

 opteran tree would have been cut off just so much higher above its 



