208 



Forty-fifth Report or the State Museum. 



The insect, deserting the hop yards in the autumn, passes to plum 

 trees, on the smaller twigs of which its eggs 

 are laid and survive the winter. Hatching 

 in the early spring [and producing the 

 " stem-mother," shown in Figure 47], three 

 broods are developed on the plum, the third 

 brood being winged. This brood at once 

 takes wing, deserts the plum trees, and flies 

 \^ to the hop yards. This flight takes place 

 \ in the month of May — in England it has; 

 been noticed on the 28th of May. 

 The precise time would, of course, vary 

 with the temperature of different seasons, 

 Fig. 47. —The hop-vine aphis, but could be ascertained by a careful ex- 



Phorodon humuli, the stem- . . . 



mother, enlarged; head and ami nation of the hop leaves daiiy at about 



antenna still more enlarged. 



(From insect Life.} the usual time for its appearance. 



When to Attack the Aphis. 

 The winged aphides [the "migrants," shown in Figure 48] would be 

 found at first on the upper leaves of the outer rows of plants in the 

 yard. This is the time, without any delay, to commence operations 



Fig. 48.— The hop-vine aphis, Phouodon humuli, migrant from plum, of the third genera- 

 tion, enlarged; head still more enlarged. (From Insect Life.} 



against them. They should be killed, and thereby prevent the enor- 

 mous progeny to which they would give rise in the nine rapidly suc- 

 ceeding generations said to have been observed on the hop -plants. 

 This multiplication, in favorable seasons, is simply appalling — almost 

 incredible, but it need not be permitted. 



It may be prevented by killing the plum-tree migrating brood while 

 upon the miter rows of the yards. 



