ILLUSTRATIONS. 



PLATES. 



Page. 

 Plate I. Fig. 1. — Nymphs and winged forms of the hop aphis (Phorodon hu- 



muli) on hop leaves. Fig. 2. — Winter eggs of the hop aphis 12 



II. Fig. 1. — Wingless progeny of winged hop aphides from alternate 

 host. Fig. 2. — Willows along edge of hopyard, which were erro- 

 neously supposed to harbor hop aphides 20 



III. Fig. 1. — Normal hop cones and hop cones injured by the hop aphis. 



Fig. 2. — Vines severely injured by the hop aphis, showing lack of 

 growth as compared with uninjured vines 20 



IV. Fig. 1. — Hopvines severely injured by the hop aphis, and left in the 



field. Fig. 2. — Enlarged view of damaged and moldy hopvines. . 20 

 V. Fig. 1. — Eggs of Hippodamia convergens among hop aphides. Fig. 



2. — Syrphus fly larva? feeding upon the hop aphis 20 



VI. Fig. 1. — Hindu laborer cooking flour paste. Fig. 2. — Boiling and 



mixing plant used at Independence, Oreg 28 



VII. Fig. 1. — Hand pump and barrel on sledge. Fig. 2. — Knapsack spray- 

 ing machine in use in hopyard 32 



VIII. Fig. 1. — Power outfit on narrow truck, in use in hopyard. Fig. 2. — 



Filling power outfit from improvised supply wagon 32 



IX. Fig. 1. — Compressed-air spraying machine, showing air bottle, tank, 

 reducing valve, and pressure gauge. Fig. 2. — Filling air bottles 



for compressed-air spraying machine 32 



X. Fig. 1. — Hopvine stripped, and tied below the point of stripping, 

 showing free condition of all foliage. Fig. 2. — Hopvine stripped, 

 and tied above the point of stripping, showing matted condition 

 of lower foliage 36 



TEXT FIGURES. 



Fig. 1. Field cages so placed as to catch any hop aphides that might emerge 



from eggs deposited upon the hop roots 11 



2. The hop aphis (Phorodon humuli): Wingless viviparous female 13 



3. The hop aphis: Winged female migrant 14 



4. Head of the hop aphis, showing frontal tubercles 15 



5. Head of the melon aphis (Aphis gossypii) 15 



6. The hop aphis: Nymph, showing wing-pads 17 



7. Diagram showing relative number of aphides in different parts of a 



single hopyard, indicating the increased infestation near Santa Rosa 

 Creek 20 



8. Short-pole hopyard, showing dense foliage around base of vines, which 



harbors the hop aphis 36 



7 



