10 FARMERS BULLETIN 804. 



The offspring of the stem-mother may either become winged or 

 remain wingless, and this condition may continue for at least 7 gen- 

 erations, so that during these generations both winged and wing- 

 less forms are to be found upon the apple. Occasional colonies of 

 wingless forms (fig. 2, a) may be found throughout the summer upon 

 the apple. The Avinged forms, however (fig. 2, /, last immature stage, 

 or pupa; fig. 2, e, adult) when mature fly to plantains and settle upon 

 the underside of the leaves, or upon the flower stems, where they pro- 

 duce young (fig. 2, g). They live principally upon the species 

 known as rib grass, long-leafed plantain, or buckhorn plantain.^ 

 This migration to the plantains continues, in the vicinity of Wash- 

 ington, from the middle of May until the first part of July. On 

 the plantains the insects continue to reproduce during the summer 

 months. Most of the forms produced on these plants are Avingless, 

 although a few Avinged ones occur throughout the summer. The color 

 of these forms is yellowish green, in contrast to the pink or rosy color 

 of those upon the apple. From 4 to 14 generations of the summer 

 forms occur upon plantain in the vicinity of Washington. 



In the middle of September winged forms, consisting of fall mi- 

 grants (agamic females) and males, begin to appear upon the plan- 

 tains. These winged forms are able to live and reproduce only upon 

 apple trees or closely related species. The fall migrants leave the 

 plantains and settle upon the underside of the apple leaves, where 

 they produce the young egg-laying females. These egg-laying fe- 

 males are wingless and pale yellowish. The males, which are similar 

 in color to the fall migrants, often being nearly black, fl}^ from the 

 plantains and find the egg-laying females upon the trees. Here 

 mating takes place and the females deposit their eggs about the 

 middle of October. As later females are produced by later mi- 

 grants, egg-laying continues until freezing weather has killed all the 

 females. 



THE GREEN APPLE APHIS.^ 



The green apple aphis lives on the apple throughout the year, and 

 infests the tender terminal growth, causing the leaves to curl, as 

 shown in figure C, «, and figure 7. In young orchards by midsummer 

 the shoots and leaves of the trees may be more or less generally in- 

 fested, often so much so as decidedly to check the growth. Such 

 trees are likely to be more or less sooty in appearance and overrun 

 with ants. Water sprouts and the shoots of top-worked trees are 

 especiall}^ liable to attack. This is the species commonly present on 

 the shoots of apple nursery stock, and much complained of during 

 some years. The work of this aphid is at times confused with that 

 of the apple leafhopper,^ which distorts the leaves in a manner more 

 or less similar. 



^ Plantago lanceolata. -Aphis ponii DeGecr. ^ Empoasca mali Le Barou. 



