434 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. 55. 



side first. It therefore seemed necessary to rear each species sepa- 

 rately, under confinement. To accomplish this the different species 

 of grass and grain stems that were found to be infested were care- 

 fully isolated. Upon closer examination, however, it was learned 

 that there were often two distinct types of injury upon the same 

 species of plant. Larvae were found occupying distinct warty or 

 gall-like distortions along the stems and others were found in the 

 center of the stems, just at the nodes. These were then separated 

 according to the manner of injury to the plant and each kind iso- 

 lated. Upon the emergence of adults, individuals from each source 

 were confined upon healthy growing plants of the same species from 

 which they had been taken. The writers found that each lot of indi- 

 viduals continued to breed in the same manner, either ahvaj^s inhabit- 

 ing the center of the stem or forming galls, as the case might be. 

 The experiments then proceeded a step further; each gall-inhabit or 

 from a given plant was tried on a series of different hosts. This 

 same method was also used for those that inhabited the center of the 

 stems. The results of these tests over a number of years proved that, 

 V, ith a few exceptions, each species steadily refused to accommodate 

 itself to a strange host. 



Unfortunately the writers have been unable to rear in confinement 

 all species dealt with in this paper, and they have never even had 

 the pleasure of observing living specimens of poophila, agropyro- 

 cola, agrostidis, ir^OTnicola, elymopMla, elymoxena, and gillettei. 



There are five species that seem to be distinctly western and have 

 steadily refused to breed here in the Eastern States. These are 

 ovata, ru-fipes^ hesperus., occidentalism and elymophthora. On the 

 other hand, there are 10 species that have never been taken west 

 of the western boundary of Missouri, namely, tritici, secalis, hordei, 

 poae, captiva, dactylicola, festucae^ atlantica^ elymicolam and macu- 

 lata. The remaining seven species, vaginicola, both forms of grandis^ 

 'LDebsteri^ alhoviaculata^ and elymi^ are found very nearly all over the 

 United States where their hosts normally occur; elymivora and 

 agropyrophila have been found as far west as Kansas. 



After breeding had apparently definitely established the distinct- 

 ness of a species, it was studied carefully for structural characters 

 upon which to differentiate it. The saws or ovipositors seemed to 

 offer the most secure basis, in that there was less variation in this 

 character and the differences were often quite striking. 



After mounting the ovipositors of all species at hand it was found 

 that a few species were so close that there was difficulty in separating 

 them on this character alone. A careful study of external charac- 

 ters at this stage showed that every species could be readily identi- 

 fied on groups of characters based on external structure. Therefore 

 the analytical tables given herewith are based exclusively on the 



