APPLE INSECTS 



147 



The Apple Leaf-aphis 



Aphis po?ni De Geer {Aphis mali Fabricius) 



This old and common European species was not definitely 

 recognized in America until 1897, but it is now widely dis- 

 tributed throughout the United States. It infests the apple, 

 pear, quince, and hawthorn. From the small, shiny black 

 oval eggs (Fig. 154) laid mostly on the bark around the buds 

 in the fall by the 

 wingless female 

 aphids, there hatches 

 in the spring, about 

 the time the buds 

 begin to open, the so- 

 called stem-mothers. 

 These are wingless, 

 somewhat pear- 

 shaped, bright green 

 in color, and give 

 birth to a generation 

 of green viviparous 

 aphids, about three 

 fourths of which de- 

 velop into winged fe- 

 males, the remainder being wingless with long, black cornicles. 

 The winged forms (Fig. 161) spread the species to other parts 

 of the same tree or to other apple trees. About half of the next 

 generation, and some of the later generations, may develop wings 

 and migrate, but the winged forms give birth to wingless vivipa- 

 rous females only (Fig. 160) . This species lives on the apple tree 

 all the year, breeding continuously during the summer. Most of 

 these wingless, viviparous females are light green in color, but in 

 the spring some may have bright yellow bodies. In October a 



Fig. 159. — Mature apples, dwarfed and mis- 

 shapen, as a result of aphis injury when small. 



