Galls by Gall- Flies. icg 



the close of those periods ; on this account we see that 

 most galls mature in the space of a year. There are 

 some species certainly which require two years, these 

 are always bark-galls ; in the first year the rudiment 

 only of the gall is formed, and its further development 

 is arrested until the next spring, when gall formation is 

 renewed with a fresh period of vegetative activity. 



