438 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 14 



Virginia in 1915, observed a difference of eleven days between the begin- 

 ning of the hatching period oi A. avenae and that of A. pomi. Peterson* 

 studying these species in New Jersey in 1919 observed a difference of 

 fifteen days between the beginning of the hatching periods 



In Western Oregon, the hatching of Aphis pomi begins from nine to 

 fifteen days later than A . sorhi. The extreme scarcity of A . avenae in the 

 orchards under observation here has m,ade it impossible to determine the 

 exact date of hatching; however, it occurs, certainly from ten to fifteen 

 days prior to the hatching of A. sorhi. This makes an interval of from 

 nineteen to thirty days between the hatching of A. avenae and A. pomi. 



The length of the hatching period shows a similar regional variation. 

 Baker and Turner record a period of seventeen days between the hatch- 

 ing of the first and last eggs of A. pomi in Virginia. At Geneva, N. Y.* 

 in 1916. hatching began on April 26 and was completed by May 2, a 

 period of six days. At Corvallis. Oregon, in 1921, the eggs upon one tree 

 under observation began hatching March 20, and continued to hatch 

 until April 18, a period of twenty-nine days. 



Summer Activities 



The most pronounced regional difference noted in the behavior of 

 these aphis during the summer months occurred in the time of appear- 

 ance of the winged forms. 



At Geneva, N. Y., in 1916 the second generation of Aphis avenae con- 

 sisted entirely of winged individuals, and the species quickly dis- 

 appeared from the apple. Baker and Turner,^ reported 98.1 per cent 

 of the second generation winged at Vienna, Virginia in 1915. At 

 Corvallis, Oregon, in 1919 the wingless forms were very few in the second 

 generation. They became predominant in the fourth generation. 



Aphis sorhi shows a tendency in this same direction, which accounts 

 to some extent for the more serious nature of the pest under Western 

 Oregon conditions. 



During the simimer of 1919, specimens of A. sorhi were placed on a 

 young apple tree enclosed in a cheesecloth cage. This cage was kept 

 constantly moist, thus reducing the temperature, raising the relative 

 hum.idity, and inducing the tree to continue a rapid and succulent growth. 



^Baker, A. C. and Turner, W. F., Morphology and Biology of the Green Apple Aphis 

 In Jour. Agr. Research, V, pp. 955-993, 1916. 



'Peterson, Alvah, Response of the Eggs of Aphis avenae Fab. and Aphis pomi De 

 G. to Various Sprays. In Jour. Econ. Ent.. XII, pp. 363-386, 1919. 



«Parrott, P. J.,Hodgkiss, H. E., Lathrop, F. H., N. Y. Agr. Exp. Sta.Bul.431,p.40, 

 1917. 



'Baker, A. C. and Turner, W. F., Apple-Grain aphis. In Jour. Agr. Research, XVIII 

 pp. 311-324, 1919. 



