JOINTWORM FLIES. 3 



Missouri. It has been known as a serious wheat pest since 1848 and 

 it is strange that it has not extended its range into the great wheat- 

 producing States of Texas, Oklahoma, Kansas, Nebraska, the Da- 

 kotas, and farther west. At present no satisfactory explanation of 

 this fact can be offered, although the species undoubtedly will invade 

 that part of the country sooner or later. Uarmolita tritici has been 

 confused in literature with 11. Jiordei., TI. secalis., U. captiva^ H. va- 

 ginicola, H. elymicola^ and doubtless with others. It was first de- 

 scribed by Asa Fitch (3)^ in 1859 as Eurytoma tritici and was sub- 

 sequently described under several names by various authors. En- 

 tomologists disagreed for years regarding this species before the 

 phytophagous habits were definitely established. 



MANNER OF INJURY. 



A plant infested by the wheat jointworm may not show any ex- 

 ternal signs of infestation whatever, or the stems may be distorted 

 and have wartlike elevations on them (PL II, C). In any case the 

 stem at the point infested is hard and woody and where there is no 

 distortion the point of infestation may be readily detected by pinch- 

 ing the stem between the thumb and forefinger. These infested 

 places usually occur above the second or third joint from the root 

 but may occur above any joint. In badly infested fields several 

 joints may be affected and a large number of plants may fall (PI. I, 

 B), thus greatly reducing the yield. It is not necessary, however, 

 that the plants fall or lodge to reduce the yield greatly. The writer 

 has taken heads from healthy and from infested stems, carefully 

 measured them against one another, and has found that the grain 

 of the infested plants from the same number of heads of exactly the 

 same length as the uninfested were very much lighter and of much 

 smaller volume (PL I, A). 



When plants lodge or fall to a considerable extent the yield is 

 far more reduced than when the plants remain standing. In the 

 first place, the plants that fall, in nearly every case, will escape the 

 binder. Should the binder reach them they will be bound so near 

 the butt of the bundle that most of them will fall out with subse- 

 quent handling. Could they be bound securely the yield would 

 scarcely be 50 per cent as large as that from heads of equal length 

 taken from normal plants. The grains, moreover, are small and 

 somewhat shriveled. The inferior grain seems to be due to improper 

 nourishment during the growdng period. The young larvae develop 

 in the walls of the stem and disarrange the fibro-vascular bundles, 

 thus greatly weakening the stem at this point. A storm, light rain, 

 or heavy wind will cause the plant to bend over at the point of in- 



1 Numbers in parentheses refer to " Literature cited," p. 26. 



