New Yoke Agricultural Experiment Station. 367 



summer, and in favorable years for the breeding of the insects several 

 broods may occur. About the first of September sexual forms of 

 the lice appear on the trees. The male aphids (Plate XXIII, fig. 1) 

 are very small pear-shaped wingless creatures and are brownish or 

 pinkish in color. The egg-laying females (Plate XXIII, fig. 3) are 

 wingless and green in color. Both winged viviparous females and 

 the sexual individuals may be found on apple foliage well into the 

 winter. 



The rosy apple-aphis. — With this species the eggs are deposited in 

 the fall, mostly upon the trunks and larger branches of apple trees. 

 About the time the leaves unfold in the spring the young, pale- 

 colored nymphs (Plate XXIV, fig. 2) hatch from the eggs and gather 

 on the young leaves and tender shoots of the trees. These lice at 

 maturity are wingless (Plate XXIV, fig. 3) and may be recognized 

 by a reddish coloration of their bodies. These females give birth to 

 winged and wingless individuals which in turn give rise to similar 

 forms. The development of the insects is very rapid; about three 

 generations of the rosy aphis occur before the middle of June. Usu- 

 ally by the first week in July, in New York, the lice leave the trees 

 and do not again appear until autumn when wanged females (Plate 

 XXIV, fig. 1) seek the trees for the purpose of producing sexed 

 individuals (Plate XXIV, fig. 4). 



The European grain-aphis. — This species is much smaller in size 

 than the green apple-aphis and is lighter in color. The eggs are 

 found on both apple and pear trees, where they hatch as the buds 

 are expanding in the spring. Two or three generations of the females 

 may develop on the trees, after which the lice migrate to grains or 

 grasses, where they breed until the autumn. At that period winged 

 females migrate to apple or pear trees where sexual individuals soon 

 appear and deposit eggs which do not hatch until the spring. The 

 lice usually disappear from bearing fruit trees before severe injuries 

 occur, but in nursery plantings the foliage is often badly curled 

 from the attacks of the aphis and blackened by the sooty fungus 

 growing on the " honeydew." 



The woolly apple-aphis. — These insects are easily recognized on 

 account of having a white, woolly covering. (Plate XXII, fig. 1.) 

 Their bodies are of a reddish color and the females are wingless unt'l 

 the third generation when winged individuals appear and migrate to 

 other trees or parts of the same tree. These give rise to sexual 

 forms and the females deposit a single, rather large brown egg. 1 

 Recent investigations 1 indicate that the woolly aphis has as an alter- 

 nate host elm trees to which the winged females migrate in the fall for 

 the purpose of depositing eggs. The lice also live on the roots of 

 trees and these individuals supply a portion of the aerial infestation. 

 The woolly aphis hibernates in the egg, and as living individuals 

 in scars on the limbs and on the roots of trees beneath the surface 

 of the ground. 



1 Me. Expt. Sta. Bui. 203. 1912. 



