20 



Bulletin 332 



TABLE 3 

 Precipitation for February 15 to March 31, 1917 and 1918 



Feb- 

 ruary 



Precipitation 



15 

 16 

 17 

 18 

 19 



1917 



1918 



inches 



inches 



0.02 



0.43 

 0.92 



. 05 



0. 98 



2.40 



March 



1 

 2 

 3 

 4 

 5 

 6 

 7 

 S 

 9 



10 

 11 

 12 

 13 

 14 

 15 

 16 



Precipitation 



IVIarch 



Precipitation 



1918 



Inches 



'J'^ truce 



One may question the influence of humidity on the percentage 

 of hatch for the past season and claim that the smaller percentage 

 was due to the decidedly cold and severe winter (1917-18). The 

 influence of cold weather is questioned by the author for two 

 reasons. In the first place from 50 to 55 per cent of the eggs out- 

 of-doors split their outer coverings, thus giving conclusive evidence 

 that they Avere alive and lu-epariiig to hatch. In the second place, 

 on Fel)ruary 26, eggs were collected from John Barclay's orchard 

 and brought into the laboratory (70°F.) and placed in a chamber 

 which continuously registered 90 per cent moisture or even greater. 

 Of these eggs 50.5 per cent split their outer shells and 43.5 per cent 

 hatched; while a similar lot of eggs (500) from the same collection 

 were kept out-of-doors where the humidity on some of the days 

 (March 15-31, 1918) registered 40 per cent or below at mid-day, 

 and showed only a 29 per cent hatch, or a difference of 14.5 per cent 

 when compared with the indoor experiment. This difference in 

 percentage of hatch is accounted for by the decided difference in the 

 percentage of moisture. 



The foregoing experimcrit, the important observations on the 

 morphological changes which take place in the egg before the 

 nymphs emerge, the records made on the percentage of hatch of 

 A. avence during the decidedly different seasons of 1917 and 1918 

 (March 15-31), the i-esults obtained from the experiments conducted 

 with controlled moistures in the incubators during 1917, and the 

 significant facts observed with skinned and normal eggs under 

 laboratory conditions, make us conclude that the percentage of 

 hatch among eggs of apple aphides is influenced to a considerable 



