February, '17] PHILLIPS: isosoMA investigations . 141 



concerning their life history. The other species has refused to breed. 

 Other members of the Division have, from time to time, sent infested 

 grass stems from various points in the Western States, from which 

 additional species have been reared. Strange as it may seem none of 

 the strictly western species will breed in confinement here in the East, 

 though repeated attempts have been made to rear some of them. On 

 the other hand, I. tritici, which is the most economically important 

 species in the East, has not been found in the great wheat belt of the 

 West. No satisfactory solution of this problem has as yet been worked 

 out. When this is done it may offer valuable suggestions for the con- 

 trol of the species here in the East. There are twenty-three distinctly 

 recognizable species known to the writer at present, occurriilg through- 

 out the United States, 5 of which appear to be strictly western species, 

 12 strictly eastern and 6 that overlap. There are undoubtedly a 

 large number of new species among these, but no attempt has as yet 

 been made to describe and name them, nor will this be attempted 

 until a critical examination has been made of all types of American 

 species. 



Quite a striking illustration of what may be a new species is one that 

 the writer has had under observation since 1912, having reared it 

 from wheat stubble collected in Pennsylvania, New York, Ohio and 

 Michigan. This species has been reared only from galls in the leaf- 

 sheath surrounding heads of wheat, and there are occasionally root- 

 like growths from the base of the gall downward (See PI. 9, fig. 2). 

 The head is always empty, no grain ever developing in plants thus 

 attacked. The late Prof. F. M. Webster has repeatedly described to 

 the writer the root-like projections he often used to find at the base of 

 some galls. At that time he supposed these galls to be the result of 

 the work of I. tritici. In 1903 Professor Webster published a paper ^ 

 on Isosoma or joint worms and illustrates injury to a wheat plant that 

 closely resembles the work of the species in question, though he used 

 this to illustrate the work of /. gj-ande. 



This new type of gall is clearly represented on the front page of 

 Bulletin 226, published in 1911 by the Ohio Agricultural Experiment 

 Station, although it was intended to illustrate the work of /. tritici. 

 The plant is affected in an entirely different manner by I. tritici 

 (PL 9, fig. 3), and the two species also differ both structurally and 

 in their life-histories. /. tritici pupates in the fall, males occur in 

 abundance, and the galls are always in the wall of the stem; the 

 former species pupates in the spring, no males having occurred in 

 three years continuous rearing, and the galls always occur in the leaf- 

 sheath surrounding the head and there are occasionally root-like 



lU. S. Dept. Agr. Div. Ent., Bui. 42, p. 18, Fig. 5. 



