Insect Galls 



1 Leaves of poplar, Populus tremuloides, showing 

 numerous globose red-tinted galls from which Mycodiplosis 

 p o p u 1 i f o 1 i a Felt was reared. (Original) 



2 Cyme of elderberry, Sambucus canadensis , show- 

 ing several enlarged blossoms infested with maggots of the 

 elder flower midge, Youngomyia umbellicola 0. S. 

 (Original) 



2l6 



