HEMIPTERA. 169 



conveys them into these burrows, and there watches and protects 

 them. In a short time after the lice have been transferred to the 

 roots of the corn, they mature a winged generation, by means of 

 which adjacent fields may be stocked. These facts indicate the 

 inadvisability of planting corn on a field that was infested by this 

 insect the previous year. The species of Aphis that has attracted 

 the most attention recently is Apliis mdli. This has occurred in im- 

 mense numbers on the young leaves of apple. Usually the injuries 

 of this species are confined to the terminal shoots of a few branclu s ; 

 but in seasons favorable to its development, the entire tree becomes 

 infested. It is necessary then to resort to the use of alkaline washes. 

 (See Chapter XIV.) 



Myzus. Two species of Myzus are very common. One of these, 

 the Cherry-tree Aphis, J. rasi, infests the leaves and twigs of 



cherry. Sometimes it becomes so abundant that it completely covers 

 the infested tree. The other species referred to is the Peach-tree 

 Aphis. Mvzus fcrsicie. This lives on the under side of the K. 



ing them to thicken and curl. Its injuries are usually confined 

 to the terminal portion of a few branches. The easiest way to 

 destroy this pest is to dip the infested branches into a pail of soap 

 solution. There is a serious disease of the peach which causes the 



es to curl in a similar manner, and which is known as the curl- 

 leaf. This disease can be distinguished from the injuries of the 



vh-tree Aphis by the absence of plant-lice in the curled lc., 

 It is caused by a fungus known as fcxoascus dcformans. 



The H.p Aphis, riiorodou humuli. This species often swarms in 

 hop-yards to such an extent that it seriously injures the crop. An 

 interesting and important feature in its lite-history is that it p.i 

 the winter on plum-trees. As soon as the leaves of plum appear in 

 the spring, the first generation of this Aphid hatches from the winter 

 eggsonplum. The first and second generations are win: nnic 



females, which live upon the plum; the third a; .rly in June, 



mged, and migrates to the hops. From tl: ration ti 



aerations of wingless, agamic females. Of tl 



tin- be, according to Kiley's observations, upon which this 



account is based, as many as eight, making tin last one the < lew nth 

 of the season. Late in August and early in September the offspring 

 of t' nth generation and of the members of the other gen 



tions that are still alive become winged. These winged indivic 

 are agamic females which migrate to plum-trees and there produce 

 wingless, sexual females. Late in Sept :liere is produced on 



