146 A}iuals Entomological Society of America [Vol. Ill, 



Continued ()l)Scrvations, both in the woods and on small potted 

 hirchcs to which the insects were transferred, removed, however, 

 all doubt as to the close relationship of these aberrant forms. 

 This generation develops in time into the return migratory gene- 

 ration." 



The return of the migrants to the witch hazel is described by 

 Pergande as follows (p. 21): "Having cast their fourth or final 

 skin, they acquire wings and, after feeding for some time to com- 

 jjlete maturity, forsake the birch and migrate back to witch hazel 

 to deliver themselves of the ultimate or se.xual generation. Each 

 migrant, according to size, contains from seven to fifteen or per- 

 haps more larvae. Migration continues for about a month and 

 a half, according to conditions of the season and other natural 

 causes, and commences usually toward the end of August and 

 tcmiinates during the early part of- October. In general appear- 

 ance they are essentially the same as those of the spring migrant 

 from the witch hazel, though they are uniformly smaller * * * ." 

 From these statements it appears that Pergande has obser\-cd 

 not only all the intermediate stages between the young of the 

 s])ring migrants from the witch hazel and the aleurodiform genera- 

 tions on the birch, but also the development of the return migrant 

 from the aleurodiform indix'iduals on small potted birches in 

 confinement. 



