25 



age in Virginia as so late as 1859 he expressed astonishment that he was 



unable to rear an}" Hessian flies from 



the same straw from which he reared 



the joint-worm. Surelj^ the unento- 



mological farmer might be pardoned 



for falling into the same error until, 



at least, he is placed in possession of 



some way of distinguishing them from 



each other. 



After iinding out bej'ond question 

 that this is a valid species, that it is the 

 true joint-worm fly attacking wheat 

 and not barle}-, while Isosoma hordel 

 attacks barley and not wheat, notwith- 

 standing the effect on the straw is much 

 the same, and that though it resembles 

 h(m)iua grunde rather closely, it is 

 quite different in habits and life his- 

 tor}^, we are forced to conclude that 

 we reall}^ know very little about it. 1 

 have reared it in limited numbers from 

 wheat straw in Illinois, Indiana, and 

 Ohio, though it would appear that 

 about 1885 it became excessively abun- 

 dant in some parts of Michigan, and, 

 in fact, I am not sure but that I have 

 myself found the larvje in some abun- 

 dance, but supposed them to belong to 

 the preceding species. The uncer- 

 tainty in regard to the identity of these 

 larva3 was owing to the fact that at the 

 time they were observed this was not 

 considered a valid species, and I at that 

 time considered them as belonging to 

 Isosoma grande, but now doubt my 

 former opinion from the fact that this 

 species does not always form galls 

 either in wheat or Elymus, that there 

 were several larvpe between the joints 

 instead of one, and that the}' Avere 

 located just under the inner walls of 

 the straw, but not forming a cell, 

 whereas those of the species last con- 

 sidered is found only in the center of 

 the straw, in the more solid sub- 



,. , , ., . . Fig. 9.— Effect of joint-worm in wheat straw 



stance, inmiediately above the JOmt (drawn in Division of Entomology) . 



