73 



608. HOP PLANT-LOUSE. 



Phorodon humuli. 



Unaffected Hop Plant. 



A spray of hops, modeled in wax, representing the plant as it ap- 

 pears in vigorous growing condition, and free from the attacks of its 

 principal enemy, the Hop Plant-Louse, to contrast the stronger foliage 

 and more abundant and larger hops produced by plants from which 

 the hop louse has been eradicated by the use of proper remedies. (Sec 



Xo. 198.) 



609. HOP PLANT-LOUSE. 



Phorodon humuli. 

 Affected Hop Plant. 

 A spray of hops modeled in wax, representing the vine as it ap- 

 pears when attacked by the Hop Plant-Louse, showing the blackening 

 and discoloration of the leaves and the small and inferior hops, which 

 are also discolored and otherwise unsuitable for market. 



610. HOP PLANT-LOUSE. 



Phorodon humuli. 

 Winter eggs. 

 Enlarged model in papier inache of the winter eggs, which are at- 

 tached by the sexual female to the terminal twigs of the Plum, in crev- 

 ices around the buds. 



611. HOP PLANT-LOUSE. 



Phorodon humuli. 

 Stem-Mother. 



The stout female plant-louse shown in this papier mache* model 

 hatches from the winter egg and is characterized by shorter legs and 

 honey-tubes. It gives birth without the intervention of the male to 

 living young, of which three generations are produced on the plum 

 tree, the last being winged and migrating to the hop. 



612. HOP PLANT-LOUSE. 



Phorodon humuli. 

 "Winged Migrant. 



This model represents the first winged generation, the third pro- 

 duced on the Plum. It instinctively flies to the hop plant and is the 

 progenitor of from five to twelve wingless generations of virgin fe- 

 males, which people the hop plants until autumn and are the sole 

 forms which depredate on the hop. In autumn the last generation pro- 

 duces again winged females, which fly to the plum trees. 



612a. HOP PLANT-LOUSE. 



Phorodon hunuili. 

 Hop-affecting stage. 



This model represents the structure and appearance of the five to 

 twelve wingless generations of virgin females which people the hop 



