28 



reared from this particular Isosoma, even where the grass infested b}^ 

 its particular host was growing in the midst of Elymus, literall}^ alive 

 with the larv» of three other species of Isosoma. Thus, while some 

 parasites attack all of the species, there are evidently others that 

 restrict themselves to one. 



REMEDIAL AND PREVENTIVE MEASURES. 



Owing to its possessing wings wherebj^ it is capable of flying readily 

 from one tield to another, or breeding in the stems of grasses in the 

 intervening territory, a rotation of crop will be less effective in the 

 case of this species than with the preceding. For the same reason, 

 careful attention to roadsides, borders of fields, and ditches becomes all 

 the more imperative. The burning over of the stubble tields l)efore 

 preparing the ground for wheat again in the fall, or the same treatment 

 of the uncultivated areas above mentioned at any time during winter 

 or early spring will eti'ectually exterminate these insects where these 

 measures are carried out. In the Middle West wheat seldom follows 

 wheat on the same ground for a series of years, the grain being rotated 

 with red clover, which prevents the burning over of the stubble fields 

 in the fall, but does not in an}' waj" affect the treatment of grass lands, 

 and if the crop is rotated annually and the borders and waste places 

 attended to there is little likelihood of the farmer suffering greatly 

 from the depredations of this insect. I have invariably found the 

 most serious injuries to occur on thin or poorly fertilized soils or 

 where the land had not been thoroughly prepared before seeding. 

 Probably whatever tends to produce a healthy, vigorous growth of 

 the wheat plant will tend to discourage oviposition by the insect. It 

 is not known that the insect prefers one variety of wheat to another, 

 but the varietj'^ with the stoutest straw will probabl}" suffer least from 

 attack. 



DIFFICtTLTY IN RECOGNIZING THE SPECIES. 



I have made no attempt to describe the larva and pupa in their proper 

 place, because I do not believe they can be separated by any descrip- 

 tion from those of the preceding species if in wheat, or those of Isosoma 

 elymi French if in grass. Notwithstanding this the farmer can readily 

 separate them at the proper season of the j'ear, even if both are present 

 in his cultivated fields. After October this species will be in the form 

 of a yellowish white larv^a in the stubble, while the preceding species 

 will be in the form of a black pupa, both perhaps in the center of the 

 stubble. In spring the larvee of this species will change to a jet black 

 pupa, while those of I. grande will have developed and escaped. So, 

 then, pupaj found in the fall will probably belong to the preceding 

 species; those found in spring, if in wheat, to this, and larvae found 

 after October, if in wheat stubble, also to this species. Howev^er, 



