XIt] Aphides and Savwflies 159 
At this time of the year no eggs are laid. Instead 
changes go on inside the mother who gives birth to 
living young. These begin to feed on the juices of the 
plants and in less than a week they may also give birth 
to young. In this way a large number of broods are pro- 
duced during a season, indeed one green fly is capable 
of producing several millions in a very short time. 
During the summer we find winged forms together 
with the wingless ones (see Fig. 48). 
The winged forms are also females, no males 
Fig. 48. Wingless and winged Aphides. (Magnified.) 
being produced at this time of the year. They also 
give rise to living young and serve to spread the 
aphides from one plant to another as one host plant 
soon becomes overcrowded. It is only at the end of 
the season that males are produced. They may be 
either winged or wingless and are born together with 
the females. Pairing takes place and the fertilized 
females do not produce living young but lay eggs. 
These do not hatch out at once but are capable of 
resisting the cold weather of winter; in spring they 
give rise to the wingless females who give birth to 
