-- 137 — 



within the burrowed parts ; in the majority of cases this must 

 liave been above the third joint ; it xwaj have been so in all cases 

 excepting Nos. 13, 18, and 20, counting from the left. 



Note 4 : On the Development of the Larvae. — I made observa- 

 tions to determine the rate of development of the larvae and the 

 date of their maturing. Especial pains was taken to determine if 

 au}' considerable proportion of the larvae failed to mature in time 

 to descend to the ground before the grain was cut, as bearing on 

 the artificial dissemination of the species. 



The data given on page 131 indicates a short duration of the 

 ^^^ state and a rapid development of the larvae. It should be 

 borne in mind, however, that those observations were made in the 

 Insectary upon specimens whose development had been accelerated 

 by the heat of the greenhouse. In the field the corresponding 

 changes took place much later. 



After the appearance of the adult flies in the Insectary, I made 

 frequent observations in the field. The following are the more 

 important results : 



Careful searching in the fields failed to reveal the presence of 

 any adults till May 25th. Then they were found to be quite com- 

 mon in a field of young clover which was last year's wheat field. 

 The insects had pas.sed the winter in the wheat stubble in this 

 field and had not yet migrated from it. Although I took fifty 

 specimens in twent}- minutes by sweeping in this field I could not 

 find a single specimen in the nearest wheat field. 



On May 29th the Saw-flies were found for the first time common 

 in the wheat field. Both sexes were found, but the females were 

 much more abundant. The specimens were found especially in 

 that part of the field nearest the clover field. At that time the 

 heads of wheat were just beginning to project from the sheath 

 formed by the upper leaf. This was true of probably 4 per cent, or 

 5 per cent, of the stalks. 



On June 29tli the wheat was beginning to turn brown. On that 

 date all of the wheat stalks were gathered from one square yard 

 of the field and each stalk examined. Thirty of the stalks were 

 found to be infested. Careful notes were taken of the position of 

 each larva and the extent it had bored. The results are repre- 

 sented graphically in Table I. A study of this table shows that 

 the greater part of the larvae were in the upper part of the stalks ; 



