Som;-: I:\rr()R'i.\xT Orchard Plant Lick ii 



very common everywhere throughout the orchard." It is thus 

 seen that for two years in the Barclay orchard, the rosy aphis 

 hatched after the leaves began to emerge from the buds and at 

 a time when shelter from spraying materials could be had. The 

 second generation of the oat aphis developes wings and migrates 

 from the apple to various grasses (species of Poa). Here they 

 breed throughout the summer. It is thought that they pass the 

 winter on grains and grasses and do not return to the apple 

 until the second fall. At any rate, in the fall ( late September 

 or early October) winged forms of this species begin to appear 

 on the apple, males and females are produced, and fertilized eggs 

 are laid on the tree. Egg-laying may continue until December. 

 The species mav l)e found la}'ing eggs on pear, ([uince, haw- 

 thorne, and plum trees. 



The third generation of the rosy aphis is winged and migrates 

 from the trees about the middle of June to plantains, where it 

 remains throughout the summer, returning to the apple in late 

 October and earlv X^ovember. ]\Iales and females are produced 

 bv the returned migrants and fertilized eggs are laid to pass the 

 winter. 



The green apple aphis lives on the apple, pear, ([uince, and 

 hawthorne, especially the first, throughout the summer. The 

 winged forms seem merely to spread the species to other parts 

 of the tree or to other trees. In the fall (October) males and 

 females are produced and fertilized eggs are laid for winter. 



\\'hen the eggs are first laid they are yellowish in color and 

 gradually become darker until they assume the normal shining- 

 black appearance. 



It thus appears that the apple suffers from the oat and the 

 rosy aphis during the early stages of fruit production onl) ; 

 the former leaving when the apples are just well set and the 

 other in June. The green aphis, on the other hand, is on the 

 trees continuously throughout the season. 



Perhaps the most puzzling phase of the aphis problem is the 

 fact that the plant lice are bad one year and hardly noticeable 

 the next. The explanation for this puzzle appears to lie in the 

 eft'ect of the weather upon the aphids and their natural enemies. 



The natural enemies of apple plant lice may be placed in i\\ ^ 

 general groups — the parasitic enemies, which usually lay their 

 eggs inside the body of the aphid, from which comes a grub that 

 eventually destroyes the aphid, and the predaceous enemies, that 

 attack, kill and consume the lice. The principal members of the 

 first group belong to the / 1 yiiiriin/'tcra. or the group of bees, ants 

 and wasps. These parasitic forms are usually very small and 

 very greatly influenced by weather conditions. 



