60 N. H. AGR. EXPERIMENT STATION, [Bulletin 171 



or on fruit. They can be caught with the thumb and finger. On 

 a sunny day, under conditions that would be expected to quicken 

 activities, they are more alert, but even here the sluggish trait is 

 rather pronounced. 



Flies disturbed by the collector do not dart awa}^ for an in- 

 stant to return shortly to the same spot, but if they do take their 

 departure seem usually to fly upward toward higher parts of the 

 tree, and to remain there. 



It cannot be said that the flies invariably prefer either sun- 

 shine or shade. Thej'' are found in both situations. In 1910 

 100 apples were picked from a Porter tree at Durham. Fifty of 

 these were selected from sunny parts of the tree; 50 from shaded 

 parts. Examination of the fruit showed 117 egg punctures in 

 the apples from the sunny situations and 168 punctures in the 

 apples from shade. 



The observation has been made by one or two who have stud- 

 ied the species and by a number of growers that the flies seem not 

 to thrive in locations exposed to strong winds. This may be 

 true under some circumstances; but it is the belief of the writer 

 that usually there are other factors in such instances, notably 

 the varieties of fruit concerned, or sometimes the fact that unin- 

 fested trees standing on hill-tops are in pastures, where live stock 

 keep the drops picked up. The reverse condition often accounts 

 in part for bad infestation of trees located in sheltered situations 

 near to farm buildings. 



THE EGG. 



The position of the egg in the apple has already been noted in 

 the discussion of the process of egg-laying. 



The duration of the egg stage was observed in 1911 by noting 

 adults at work laying eggs, and marking the puncture. The 

 fruit was then removed for further observation. The time of 

 hatching was determined in two instances. In each the period 

 was five days. This was in early September. 



Ross (55), in a series of similar determinations found a period 

 of four and three fourths to nine days, with an average of six. 

 This was under normal surroundings. 



Illingworth (34, p. 144) observed an incubation period of two 

 to six days. In this case the eggs were removed from the apple 



