1920] 



Peterson: Hatching of Aphid Eggs 



395 



outdoor environment. In other words, air of high moisture 

 content, as in the moist chambers, is more favorable for hatching 

 than the normal indoor or outdoor air having a lower moisture 

 content. 



In Table 2 it will be noted that the percentage of hatched 

 eggs of A. avencB brought into the laboratory on February 11, 

 1919, is very low. This experiment and others of a similar 

 nature show that the eggs of this species usually will not 

 give a normal percentage of hatch when they are brought 

 into the laboratory too early in the season. In this respect 



TABLE II. 



Percentage of hatch of the eggs of A. avencB and A. pomi under different tem- 

 peratures and moisture conditions in 1919 and 1920, at New Brunswick, N. J. 

 500 eggs in each lot. 



they are somewhat similar to the eggs of A. pomi, which refuse 

 to hatch if brought into a warm room earlier than 20-30 days 

 before the normal outdoor hatching period. 



In addition to the foregoing experiments on the response of 

 the eggs to controlled moisture the author has made observa- 

 tions on the percentage of hatch of A. avence and A. pomi at 

 New Brunswick for four seasons, 1917 to 1920. Table 4 gives 

 observations for four seasons with the eggs of A . avence, showing 

 the percentage of hatch and also the percentage of eggs with a 

 split outer shell at the time hatching is rapidly taking place. 

 The percentage of hatch varied considerably during the four 

 years, yet these variations are probably due to the evaporation 

 factors of the weather for the respective years. Unfortunately 



