Insect Galls 



i Leaves of poplar, Populus tremuloides, showing 

 numerous globose red-tinted galls from which Mycodiplosis 

 populifolia Felt was reared. (Original) 



2 Cyme of elderberry, Sambucus canadensis , show- 

 ing several enlarged blossoms infested with maggots of the 

 elder flqwer midge, Youngomyia umbellicola O. S. 



(Original) 



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