PLATE XI. Aphid Galls. 



1. Mordwilkoja vagabundus Walsh, — ^vagabond poplar gall, x i. 



2. Pemphigus populicaulis Fitch, x i. 



3. Hamamelisies spinosus Shimer, x i, 



4. Hormaphis hamamelidis Fitch, x i, 



5. Phylloxera caryaecaulis Fitch, — hickory aphid gall, x i. 



6. Chennes cooleyi Gillette, x i. 



7. Chermes abietis Linnaeus, — spruce aphid gall, x i. 



Photographs by B. H. Walden. 



