APHIDS INJURIOUS TO ORCHARD FRUITS. 



15 



In the autumn migrants are produced on grains. These mature in 

 about 2 weeks and return to the apple, the migration lasting 3 or 

 4 weeks, since not all the migrants are produced in the same gen- 



FiG. 11. — The oat aphis: Winged agamic female, greatly enlarged, 

 still more enlarged. (Davis.) 



Antenna of same, 



eration. During their life of some 6 weeks these migrants produce 

 about 5 egg-laying females each. 



The winged males are produced upon -the summer food plants and 

 migrate to the apple leaves to mate with the sexual females. After 

 the female has become fertilized she deposits 

 her eggs in crevices of the bark of the larger 

 branches or behind the bud scales of the young- 

 twigs of the apple. (Fig. 12.) The length of 

 life of each sex depends upon weather condi- 

 tions. This is particularly true of the female, 

 which sometimes lives for weeks in a more or 

 less dormant state during cold weather. In 

 warm climates the species may hibernate as 

 wingless females upon the summer hosts. 



THE CLQVER APHIS.> 



The clover aphis, first found injurious to the 

 apple in Colorado, is now known to occur abun- 

 dantly in some regions in the East. It attacks 

 the apple in a way similar to the green apple 

 aphis, but since there is a considerable migration 

 of individuals to clover, it is less abundant on 

 the apple in summer than the latter species. 

 The stem-mothers of the clover aphis are pink and the individuals of 

 the next generation are yellowish green. The winged forms have 

 a large black patch on the abdomen and in this way resemble the 



Fig. 12. — The oat aphis : 

 Winter eggs on hark 

 of apple tree. Much 

 enlarged. (Original.) 



Apliis bnl;('ri Cowan. 



