398 Annals Entomological Society of America [Vol. XIII, 



eventually hatched. In other words, 30 per cent more hatched 

 than had split their outer coats at the hatching period. This 

 condition is quite opposite to that of 1918. The author is of 

 the opinion that evaporating factors have a decided influence 

 on the outer coat. Conditions producing high evaporation 

 probably make the outer shell brittle and easily broken by the 

 growing embryo within, while low evaporating conditions tend 

 to make the outer shell elastic, thus permitting greater expansion 

 before it breaks. If the above is true then an early rupture of 

 the outer coat is apt to be detrimental, for it exposes the 

 permeable membrane to evaporating factors for a long period 

 of time, while a delayed rupture in the outer coat is beneficial 

 since the inner pervious membrane is exposed to evaporating 

 factors for only a short period of time. Briefly stated, the 

 above observations show that an early split of the outer coat, 

 which is usually followed by a low percentage of hatch, is 

 probably brought about by the existence of high evaporation 

 during the susceptible period, while a delayed splitting, which 

 in turn may be followed by a high percentage of hatch, is 

 probably brought about by the existence of low evaporating 

 factors during the susceptible period. 



From the above experiments and observations made on the 

 percentage of hatch in variable seasons, the author concludes 

 that variations in the moisture content of the air largely 

 determines the percentage of hatch of fertile eggs and probably 

 influences the rate of split in the outside coat of the eggs. In 

 other words, the moisture content of the air influences the evap- 

 oration of the water content of the eggs, determines the percent- 

 age of hatch and probably influences the rate of split in the 

 outside coat. 



TEMPERATURE. 



No extensive experiments were made to determine the 

 influence of temperature (as a factor in evaporation) upon the 

 percentage of hatch. A few observations were made in respect 

 to the influence of temperature on the rapidity of the splitting 

 of the outer layer and the hatching of the eggs. During the 

 past season 500 eggs of A. avence were collected on March 

 6, 14, 20 and 24, from each of four orchards located near 

 Bridgeton, Glassboro, Riverton and Cranbury (See Map, Fig. 5). 

 These orchards are located in the southern half of the state 



