LETTER OF TRANSMITTAL 



U. S. Department of Agriculture, 



Bureau of Entomology, 



Washington, D. C, October 22, 1910. 



Sir: I have the honor to transmit herewith a manuscript entitled 

 "The Genotypes of the Sawflies and Woodwasps, or the Superfamily 

 Tenthredinoidea." These insects belong to this superfamily of 

 the order Hymenoptera and include some of the important enemies 

 of North American forest trees. The true sawflies, in their larval 

 stage, destroy the foliage of coniferous and other trees and forest 

 growths and some of them are exceedingly destructive, as, for example, 

 the larch sawfly, which feeds upon the foliage of the larch timber of 

 Europe and North America. The woodwasps, in their larval stage, 

 bore in the wood of dying and dead standing and felled trees, causing 

 defects and rapid deterioration. 



In addition to the large number of species which are native to this 

 country, there are some very destructive species which have found 

 their way here from other countries, so that it is of the greatest 

 importance to know all of the species and to guard against further 

 introductions. 



Both the systematic and economic knowledge of these insects is 

 notably limited, especially as regards North American species, and 

 it is of the utmost importance, as a basis for the best results in investi- 

 gations of these insects in their relation to economic problems, that 

 considerable purely technical work should be done on them. 



Mr. Rohwer has been engaged to work on the sawflies on account 

 of his extended expert knowledge of this group of insects and the 

 work he had done on them before he came to the Bureau. As a 

 collaborator of this Bureau, but at his own expense, Mr. Rohwer 

 visited the principal collections of Europe in the summer of 1909 to 

 study the types of described species and genera, all of which puts 

 him in a position to carry on the research work assigned to him in 

 the most thorough manner. Mr. Rohwer has found it necessary to 

 devote considerable time to preliminary work on the entire group 

 and on the genera of the world in order to have an authoritative 

 basis for the further work of a monographic nature on the more 



