436 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 14 



The dark males follow the females to the plains and foothills, m.ate 

 during the autimi.n and die during the winter. During the spring, 

 however, most of the first brood pale green m,ales remain behind on the 

 plains and foothills and probably die after the pasture vegetation be 

 com.es dry. After a flight had occurred during the spring, 8% of the 

 specimens collected in the cultivated area were males and 92% were fe- 

 males. After the invasion of the spring brood into the cultivated area 

 Vc of the fem.ales had m.ature eggs in the ovaries. 



OBSERVATIONS ON THE BIOLOGY OF APPLE APHIDS 



By Frank H. Lathrop, Associate Entomologist 

 Oregon Agricultural Experiment Station 



It not infrequently happens that m.ethods of treatment which have 

 been used with great success in the control of insect pests in one section 

 of the country prove inadequate when applied in som.e more or less dis- 

 tant section. Moreover, certain treatments, such as oil sprays, which 

 are used with comparative safety in one section, m.ay be too injurious 

 to permit of their general use in another section or under different cli- 

 matic conditions. These apparent discrepancies may usually be 

 explained upon the basis of variation in behavior of the insect pests or 

 of the orchard trees in reacting to the dissimilar conditions of climate, 

 topography, or other environmental conditions of the two regions. 



It is therefore desirable, in the study of insect pests, to compare, 

 whenever possible, the characteristic behavior of the insects in different 

 sections of the country. 



During the seasons of 1915 and 1916. the writer had opportunity to 

 study, at the Geneva Station in Western New York, the three species of 

 aphids, (Aphis avenae Fab., Aphis .pomi De G., and Aphis sorbi Kalt) 

 which are comm,only injurious in apple orchards. Since 1917 these 

 observations have been continued in Western Oregon. This study, 

 made in districts so widely separated and so distinctly different in climate, 

 has brought out several interesting facts relative to the behavior of these 

 insects. 



Relative Abundance of the Species 



Probably the first difference to be noted is the relative abundance of 

 the several species in the two regions. 



In western New York, Aphis avenae is normally the most abundant of 

 the three species. Although the actual injury from this species is 



