55 



Normally the life-cycle is as follows : In spring we 

 start with what is called a Mother Queen or Stem 

 Mother a wingless female. This parent produces a 

 sexually living young called " lice," really the larval 

 stage. These larvae soon mature and produce other wing- 

 less females, and so on until the plant becomes smothered 

 (Plate VIII., Fig. 7, the lowest of the four Figs.), 

 and then the wingless forms develop wing-buds in fact 

 become pupae, which give rise to winged females which 

 fly off to other plants and produce wingless creatures 

 like their parents (Plate VIII., Fig. 7, the middle Fig.) 



These winged forms may fly off to the same kind of 

 plant, for instance from one Rose to another, or they 

 may fly off to quite a different sort of plant, as from the 

 Rose to corn or the teazel. 



This migration is very important to notice. 



In any case, at the end of the season there are 

 produced males as well as females. These autumn females 

 are called the oviparous or egg-laying generation, and 

 they, after having been fertilised by the males, deposit 

 eggs upon the plant. 



These eggs remain all the winter in the axils of 

 buds, on the stems, &c. They are visible to the naked 

 eye if searched for carefully on the Roses. In form they 

 are spindle-shaped, the shell is shiny and the colour 

 black (Plate VIII., Fig. 7, the upper left-hand Fig.) 



Thus we have during the summer reproduction by 

 a sexual method, in autumn sexual reproduction occurs 

 and eggs, not living young, may be produced. 



The rate of reproduction in plant lice is enormous, 

 under certain conditions. Hence the reason we find the 

 tip of the Rose shoots suddenly covered with green and 



