1914 



ENTOMOLOGICAL SOCIETY. 



79 



epidermis and either produce only a slight discoloration as in certain species of 

 the genus Cincticornia, or else excavate a fairly well defined mine such as that 

 of Lasioptera excavata in Crataegus. The globular or lobulate galls of Gincti- 

 cornia glohosa and C. pilulcB respectively, as well as the conical and globose en- 

 largements of various species of Caryorayia upon hickory must be considered as. 

 extreme types or modifications of the blister gall. 



Pig. 4.— Gall Midge Structures. 



Stem Galls. — No part of the plant is exempt from infestation by the small 

 representatives of this large family, be it seed, flower, leaf, stem or root. The 

 stem gall is usually subcortical, and in those produced by midges, development 

 generally begins while the tissues are still in a soft and plastic condition. They 

 are usually polythalamous and are frequently irregular, more or less confluent 

 swellings in the bark. 



