36 INSECT-GALLS OF THE VICINITY OF NEW YORK CITY 



sented by a cup-shaped impression on the upper side of leaf and on the under 

 side it is sub-cyhndrical, with the apex rounded bluntly. About ^ in. high and 

 ^ in. wide. On leaf of hackberry {Celtis occidentalis) . Common. 



80. Hackberry Melon Gall {Pachypsylla celtidis-cuciirhita: Riley). — Under 

 side rounded, truncated at apex and concave in the middle, with a small nipple. 

 Around the top is usually an acute ridge which surrounds the concave depres- 

 sion, and at the sides near the top are short ribs ^which are sometimes nearly 

 obliterated. Represented by a cup-shaped impression on upper side of leaf. 

 On under side of leaf of hackberry (Celtis occidentalis) . Common.* 



Family Aphidid.-e (Plant-lice). 



The plant-lice are well-known insects and infest nearly all 

 kinds of plants. Comparatively few produce galls. 



81. Witch Hazel Cone Gall {Hormaphis hamamelidis Fitch). — A conical 

 swelling on upper side of leaf of witch hazel [HamameUs virgtniana). Very 

 common. 



