PROCEEDINGS, 1915. 63 



These two questions depend upon a combination of factors, although 

 individual ones sometimes seem to have a predominating influence. Thus, 

 as a rule, it seems that the early-maturing sweet or sub-acid varieties such 

 as the Sweet Bough or Gravenstein are more seriously infested than the 

 acid fruits such as the Red Astrachan. 



Thick-skinned apples are not very badly attacked. In the same 

 badly infested orchard this summer, for instance, were Spies, Baldwins, 

 Kings, and Nonpareils, the Spies being very badly punctured, while the 

 other varieties mentioned were scarcely touched. The Northern Spy is 

 a thin-skinned apple, while the others are characterized by the thickness 

 of the skin. 



Aroma may also have an influence. When once infested, the early 

 maturing apples give the best possible chance for the maggots to develop, 

 because of the warm weather, whereas with the late fall or winter vari- 

 eties, the frost or cold weather catch the larvae before they have fully 

 developed. The growth of the maggot is closely correlated with the ma- 

 turity of the apple, as the former keeps pace with the latter. This is prob- 

 ably due to the increase in the food supply, for as the apple matures, the 

 sugar content is increased with the resultant hastening of the develop- 

 ment of the larva. 



Feeding Habits. 



As mentioned previously, the flies obtain their nourishment from 

 the gum and juices found on the surfaces of the leaves and fruit, pre- 

 ferably the latter. This is important to know, since our control measures 

 are based upon this fact. 



The mouth parts of the fly are fitted for sucking, so while all li- 

 quids are at once pumped up, solid food must first be rasped free, and then 

 being dissolved or held in suspension in the saliva of the fly, which is eject- 

 ed, the whole is sucked up. Thus, if poison is thoroughly sprayed on the 

 leaves and fruit, the vast majority of the flies will be killed. 



Relative Number of Males and Females. 



From observations taken in the orchard of the number of flies seen, 

 the proportion of males to females was found to be about 5.1. And yet 

 in our untreated cages we had a total emergence of 610 flies, 353 of which 

 were females, which makes the percentage of females as 57.8 per cent. 



Dispersion. 



In the past season an effort was made to determine how far the 

 adults fly. Two methods were used — the spraying of rosalic acid on the 

 adults, and the tying of a white silken thread to their legs as a distinguish- 

 ing mark. 



