JOINTWORM FLIES. 11 



two beyond the leaf sheath. Sometimes it does not even burst 

 through the sheath and rarely if ever do any of these heads contain 

 grain (PI. Ill, A, B, G). The larval cells are contained in the hard- 

 ened leaf sheath. 



Why this species has not become the dominant pest of wheat, at 

 least among the jointworm group, is inexplicable. It is prolific and 

 the plants attacked seldom if ever produce any grain. The species 

 has been in this country for at least 55 or 60 years. The only ex- 

 planation that occurs to the writer, of the reason it has not proved 

 more injurious, is that it seems unable to breed in strong, well-grown 

 plants. In other words, by the time the adult emerges in the spring, 

 the majority of the wheat plants are well grown and about to begin 

 heading. This is true, at least, for the States east of the Mississippi 

 Eiver. It seems necessary that plants be small and the heads in an 

 immature tender stage for this species to be able to breed in them. 

 The species absolutely refuses to oviposit in large plants that are 

 about ready to head. Should this pest once become established in 

 the spring wheat belt, the writer is of the opinion that it will be a 

 very serious pest, owing to the fact that the adults would undoubt- 

 edly emerge when the wheat plants were young and tender and most 

 attractive to them, as is known to be the case with grandis where the 

 spring and winter wheat regions overlap. 



HOST PLANTS. 



H. vaginicola steadily has refused to breed in any plant other than 

 wheat. The writer never has observed it even to attempt oviposition 

 in any other plant, and, as previously stated, the plants must be 

 young and tender or it will refuse them. 



LIFE HISTORY. 



There is only one generation a year. The larvae remain in the 

 wheat stubble until the following spring, then pupate and emerge as 

 adults in May. The abdomen of the female contains 60 to 70 eggs. 

 They are normally thelyotokous. During the 4 years the writer has 

 been rearing this species in confinement no males have been observed, 

 though thousands of specimens have been reared. 



THE BARLEY JOINTWORM.i 



The records show Harmolita hordei to be the oldest species re- 

 corded in literature in the United States, and, like tritici, it has 

 caused a storm of argument. In fact, for many years it was sup- 



1 EarmoUta hordei Harris, 



