HOMOPTERA 



429 



and 1st A of the fore wings coalesce at base (Fig, 501). The sexual forms 

 have no beak. The anus is closed. The species do not infest conifers 



PHYLLOXERINiE 



Sa^E+M+Cu + istA 



Fig, 501, — Wings of Phylloxera. (From Patch.) 



Subfamily ADELGIN^ 



The Adelgids 



This subfamily includes those insects found on conifers that have 

 been quite generally known under the generic name Chermes. But it 

 has been determined that this name should be applied to certain 

 jumping plant-lice of the family Chermidas, formerly known as the 

 Psyllidas. The necessity of this change is very unfortunate, as much 

 has been published regarding members of the Adelginae and in most 

 of these accounts they are described under the name Chermes. 



All the species of this subfamily infest conifers; and in all cases 

 in which the sexual generation is known, this generation lives on 

 spruce. The secondary host may be either larch, pine, or fir. 



Much has been written regarding the life-histories of these insects. 

 It has been found that what may be regarded as the typical life-cycle 

 of an Adelges or ''Chermes'' is a very complex one, including the 

 developing of two parallel series of forms differing in habits ; that in 

 one of these series a single host-plant, spruce, is infested and the life- 

 cycle is completed in one year; while in the other series the life-cycle 

 extends over two years and is passed in part upon spruce and in 

 part upon larch or some other host-plant. 



In this typical life-cycle, beginning with the individual that 

 hatches from a fertilized egg, there are developed five generations, 

 the members of which differ in either form or habits or both from 

 those of the other generations, before the cycle is completed by the 

 production again of fertilized eggs. The actual number of generations 

 may be greater than this, owing to the fact that in a part of the cycle 

 there may be a series of similar generations only the first of which is 

 counted in this enumeration. 



