PROCEEDING 1915 65 



weeks, while one lived for two days longer. It was noticed that the cool- 

 er the weather the longer the flies survived, so although we may not be 

 able to correctly estimate the length of life of the flies in nature, this gen- 

 eral principle holds good, that in the heat of the summer they succumb 

 more quickly than in the cool weather. 



The Egg. 



The eggs are about 1-10 of an inch long, white, and somewhat cy- 

 lindrical. They are placed singly under the skin of the apple, to a depth 

 of about 1-10 or 1-32 of an inch, and at an angle of about 45 degrees with 

 the surface of the fruit. 



Just before oviposition the female moves quid!/ o- ?r the apple, 

 apparently searching for a suitable place. Finding one, she rises high on 

 her legs and bending her abdomen downwards at almost a right angle, 

 she exserts her ovipositor and prods away at the skin. After reaching the 

 required depth she enlarges the opening in the flesh of the apple, by pry- 

 ing her ovipositor from side to side, after which the egg passes down into 

 the puncture. Different times are taken at this operation, but the aver- 

 age is about a minute and a half. The punctures becomes filled with the 

 escaping juices, which, on drying, form a white waxy plug. The first 

 punctures were noticed on July 27th and the last day we observed fe- 

 males ovipositing was on September 11th. They could not have de- 

 posited very many more eggs as the weather turned wet and cool about 

 that time. 



To determine the length of incubation for the eggs, numerous punc- 

 tures were marked just as soon as the fly had finished ovipositing, and 

 then after a lapse of a few days examination of the puncture revealed 

 whether the young maggot had hatched. In this way it was found that 

 on the average it takes six days for the egg to hatch; at this period the 

 weather was warm although of course, the nights were usually quite 

 cool. 



There is always a very great difference between the number of punc- 

 tures observed on an apple, and the number of maggots which emerge, 

 the former being much greater. This mortality is present in both the egg 

 and larval stages. In regard to the former, numerous punctures were 

 carefully opened and it was determined by the presence or absence of 

 the brown track whether or not the egg had hatched. The accompany- 

 ing table gives our results ; and it is seen there is a considerable mortality 

 among the eggs, the cause for this not being known. 



