90 N. H. AGR. EXPERIMENT STATION. [Bulletin 171 



toward the adult stage, to supplement or replace the method of 

 keeping drops picked up. 



As study of the insect proceeded it was found that there are 

 facts in its life history and habits that have a vital bearing in 

 judging the apparent benefit of any such proposed measures. 

 These facts are as follows: 



The adults of this species are not ordinarily characterized by 

 general and free flight throughout a section, as with many other 

 pests. If fruit of attractive qualities is at hand the flies are lo- 

 calized in their habits. This means that measures directed against 

 the adult stage in a given case can be interpreted only on the 

 basis of definite knowledge that there was an ample supply of 

 adults in and about the trees, capable of egg laying. 



To be certain that such supply exists one must ordinarily know : 



That there was an abundance of infested fruit on the trees the 

 previous season; 



That this fruit was allowed to decay on the ground beneath 

 the trees; 



That it was of such variety that decay would take place in 

 time to permit the maggots to mature and leave it before cold 

 weather; 



That circumstances did not exist unfavorable or fatal to the 

 pupa in the soil. 



Further facts to be recognized are the following: 



If the trees under experiment are not of variety especially at- 

 tractive to the adults, and are adjacent to others that are 

 attractive and that are in fruit, there may be a movement toward 

 the latter. 



A count of egg punctures can alone determine the actual in- 

 festation following treatment. Trees may bear a small amount 

 of fruit one season, and this fruit be so badly punctured as ob- 

 viously to be worthless. If such conditions prevail the year pre- 

 ceding treatment, and if there is a large amount of fruit the year 

 when treatment is given, not only may there be less adults be- 

 cause of unfavorable concentration the previous season, but the 

 egg punctures will be so distributed that the fruit may appear 

 fairly free, although the total number of egg punctures may be 

 the same. 



Occasionally fruit of a hard or late variety is badly attacked in 



