20 PROCEEDINGS ENTOMOLOGICAL SOCIETY 



Again, there exist in western North America tachinid spi cies 

 which seem indistinguishable on external characters, both ana- 

 tomic and colorational, from European species. Catharosia calm 

 Coq., of Idaho, can not be told from C. pygmaea Fall., of Europe. 

 It does not occur in eastern North America so far as known. 

 Cases of this class may be multiplied, but this will suffice as 

 example. These species are evidently distinct from the European. 



The purpose of this communication is to state the principles in- 

 volved in commercial dispersals, citing a few examples in illus- 

 tration; and particularly to emphasize the danger of attempting 

 to identify species outside their natural faunal limits. In mak- 

 ing determinations, for example, of European species in the 

 American fauna, the principles governing dispersal must be most 

 sr>rioiislv considered. 



HORISMOLOGY OF THE HYMENOPTEROUS WING. 



BY S. A. ROHWER, Forest Entomology, AND A. B. GAHAN, Cereal ami 



Forage Crop Insects, 



Bureau of Entomology, Washington, D. C. 



INTRODUCTION. 



Anyone who has attempted to do serious systematic work 

 in the Hymenoptera cannot but have experienced difficulty in 

 interpreting the meaning of certain authors in their description of 

 wing venation. The lack of a uniform system of nomenclature, 

 has caused the application in many cases of several names to the 

 same vein or cell, while in other instances the same name has 

 been applied to two or more different parts of the wing. Unless 

 an author has indicated the authority whom he proposes to fol- 

 low in naming the parts of the wing or has otherwise explained his 

 own system it often becomes a puzzle to be certain of his meaning. 



The difficulty experienced in such instances with the consequent 

 loss of time entailed, has caused us to feel the need of a key to the 

 synonym}*- of venational terms as well as a uniform set of names 

 to be used in our own work. 



It is the intention, therefore, to here present in so far as pos- 

 sible a complete and uniform nomenclature for the wing veins and 

 wing cells of Hymenoptera, together with a synonymical index to 

 wing nomenclature compiled from the works of the most promi- 

 nent Hymenopterologists past and present. Figures illustrating 

 all of the more striking types of venation found in the order arc 

 included. From a study of these figures it will be possible, wr 

 hope, for the student to correctly apply the nomenclature to any 

 wing in the order, and also by reference 'to the synonymical list 

 to interpret the meaning of the terms used by others in the pa-4. 



