386 REPORT OF THE COMMISSIONER OF AGRICULTURE. 



On June 6, however, I was gratified to find females of the same 

 form in considerable numbers ovipositing- in wheat about Oxford, Ind. 

 These were also provided with fully developed wings, and, in fact, I 

 have yet to see a single example wingless or even with aborted wings. 



The next day I found a pupa in a growing wheat plant, and in 

 another which was dying at the top precisely like the plant in the 

 Bloomington, 111., field, in which I found the pupa May 29, I found a 

 fully developed adult alive, and, to all appearances, about .to emerge. 



In both cases the plants had reached the height of only a few inches, 

 with scarcely any stem, but an unnatural grow th of leaf. 



The adults continued quite abundant until about the 18th of June, 

 when they began to decrease in numbers. The last one noticed was 

 taken on the 27th of the same month. 



They seemed to fly about freely, and I found them in all fields of 

 wheat or rye examined, even though the previous crop had been of 

 corn, although they were considerably more abundant where the pres- 

 ent was the third crop of wheat than where it was the first. 



In every ease, so far as I observed. They invariably oviposited directly 

 in the upper joint, aud their instinct in detecting its location even when 

 covered with the sheath was infallible. 



I feel quite confident, however, that future observations will show 

 that they do oviposit lower down in the plant earlier in the season, 

 when it is more tender. For while I have never found any indication 

 that the young larvae, after hatching, made their way downwards, their 

 track upward was very apparent in the joint, and also the actual num- 

 ber of larvae found in and above the upper joint later in the season 

 fails to correspond with the number of females observed ovipositing. 

 Moreover, I failed to find these adults any more numerous in fields 

 where last year's straw stacks were still standing than where the straw 

 had been removed and threshed elsewhere. 



My experience has been that the larvae of these Isosoma very seldom 

 work downwards into the joint until full grown, and then only to exca- 

 vate a cell in which to transform. This may at first appear to be a 

 matter of small moment, but when we find that ninety-nine out of every 

 hundred of these upper joints are removed with the straw, while, if the 

 grain is harvested at the usual height, eight out of ten of the joints 

 next below will, in all probability, remain in the field, we shall find 

 that it may make a considerable difference in the future life of the in- 

 sect whether it is located a little lower down or higher up in the straw. 



I have secured abundant material, both of larvae and of straw, in 

 which I know the larger form has oviposited, but have not yet attempted 

 to separate the two forms of larvae. 



Assuming that both are tritici, I find by a series of examinations 

 made June 25, July 1 and 9, that of 90 straws from the same field, 81 

 contained 136 larvae, the remaining nine being uninfected. 



By examining the straw at different dates, the total number of larvae 

 would include many that would have been destroyed by parasites later, 

 and also any hatched after the 25th of June. The number actually de- 

 veloping from 90 straws will be determined another year. These 136 

 larvae were distributed in the straw as follows, each joint including 

 with it the intervening space between it and the next above, or, if the 

 first, between it and the head: 



Number in first joint... 

 Number in second joint 

 Number in third joint-. 

 Number in fourth joint. 



17 

 77 



33 

 10 



