23 



sections and with some farms tne soil is but little fitted for other crops, 

 and where wheat follows wheat year after year for an indefinite period. 

 Under such conditions, burnino- the stub]>le before preparing- the 

 ground for the new crop in fall will prove effective. If this burning 

 is delayed until September, manj- of the parasites will have developed 

 and escaped. The burning can be best carried out by cutting the grain 

 as high as possible, leaving the stubble long. A few days before 

 burning a mower should be run over the field, cutting off all grass and 

 weeds, which, when dried, will add to the fuel supplied In' the stubble. 

 Taking advantage of a favorable wind, the farmer can burn over his 

 field cleanly, thereby not only ridding it of the presence of this pest, 

 but also the Hessian fl}-, liesides l>urning up nuich of the seed of foul 

 weeds and grasses. 



DISTRIBUTIOX. 



This species seems to occur throughout the middle belt of country 

 from the Atlantic to the Pacific, wherever wheat is grown as a staple 

 crop. Whether it is single-brooded in the North and is, therefore, in 

 such countries capable of sustaining itself in spring wheat, is not yet 

 known. Having no other known food plant than wheat, it will neces- 

 sarily follow that its range will be restricted to areas of wheat culti- 

 vation, and being double brooded, requires fall wheat in which to 

 develop. The fact of its having been so long confused with what now 

 seems the true joint-worm fly {Isosoma tritici Fitch) renders its actual 

 distribution, as well as the extent of its ravages in the past, somewhat 

 obscure. 1 found the summer form {(jrande) in considerable numbers 

 in spring wlieat at Lafayette, Ind., June 19, 1895, and it is likely that 

 it can breed therein, though fall wheat is necessar}' for form ininutuin. 



THE JOINT-WORM. 



{TsoKonia irltiri Fitch. Figs. 8 and 9.) 



I have previously referred to the confusion of Isosoma tr'dici Fitch 

 with I. hordei Harris, and which was so persistently insisted upon b}^ 

 Walsh and Riley. It was not until 1896 that Dr. Howard succeeded in 

 establishing the fact that this is a valid species, and now we are con- 

 fronted with a long series of complications that can only be safel}' 

 corrected by carefully rearing both species and studying them anew. 

 Failing entirely in securing sufficient material from wheat in carrying 

 out the investigations upon which this bulletin is based, I feel now 

 ver}' much like letting the insect alone until an opportunit}' is offered 

 to untangle the knotted skein. Doctor Fitch stated distinctl}^ that the 

 term "joint- worm" was to be applied to the insect attacking wheat, 

 and it was because of the mistake of considering it the same insect as 

 tha.t described b}^ Harris that the name "joint- worm" came to be 

 applied to I. hordei at all; a mistake that belongs neither to Harris 

 nor Fitch, but one that has misled nearly everybody. 



