392 Annals Entomological Society of America [Vol. XIII, 



EVAPORATION. 



The splitting of the outer coat of the egg and the percentage 

 of hatch of the eggs of A . avence and A . pomi are influenced con- 

 siderably by evaporating factors. These factors in a natural 

 environment are moisture, temperature and wind velocity. 

 This paper takes into consideration the response of the eggs to 

 moisture and temperature. 



The two layers of the egg are decidedly different in their 

 pervious nature. To determine the relative permeability of 

 the two layers of the eggs of A. avencB a simple experiment was 

 conducted in 1917; the outer semi-transparent tough layer was 

 removed from fifteen normal eggs on April 5 and the skinned 

 eggs were placed in a covered Syracuse watch glass. Fifteen 

 normal eggs were placed in the same vessel. The skinned eggs 

 shriveled completely inside of 24 hours and none hatched, 

 while 6 of the 15 normal eggs hatched in 4 days. The above 

 experiment was repeated with the eggs of A. pomi and the 

 results were approximately the same. These experiments show 

 that outer layer on the egg prevents evaporation under ordinary 

 conditions, while the inner pigmented layer is of little use in 

 preventing evaporation. If this is true then one may conclude 

 that eggs with split outer coats are more susceptible to evapo- 

 rating factors than normal eggs with whole outer layers. 



MOISTURE. 



The influence of moisture on the eggs of A. avence and A. 

 pomi was determined by incubator experiments with controlled 

 moistures and temperatures; by other experiments where the 

 eggs were placed in moist chambers under ordinary conditions 

 indoors and outdoors and by observing the percentage of 

 splitting and hatching of the eggs of A. avence for four variable 

 seasons, 1917 to 1920, and comparing these observations with 

 the weather conditions for the respective years. 



The controlled moisture and temperature experiments were 

 conducted in 1917 and 1920 in the incubators and moisture 

 control apparatus used by Dr. T. J. Headlee in his investigations 

 on the bean weevil ; the writer wishes to express his appreciation 

 for the privilege of using this efficient equipment. The incuba- 

 tors were fitted with one to three moisture control systems. 

 Each system (Figure 6) was composed of two air dryers, a 



