INSECT PESTS 155 



vetches, are affected. Attacks begin on 

 the young pea vines; the 'lice' gather in 

 clusters at first under and within the termi- 

 nals, and as the leaves become covered they 

 attack also the stems and by their numbers 

 and veracity sap the life of the plant. 

 Whole areas of vines are seen covered with 

 the aphis." 



How THE Aphids Multiply. The 

 "lice" spend the winter in the egg stage. 

 When the young sweet pea seedlings ap- 

 pear in the spring the lice hatch from the 

 eggs, and instead of being partly males 

 and partly females, all are females, known 

 as stem mothers. These without the in- 

 tervention of the male give birth to a sec- 

 ond generation, all of which are likewise 

 females. These females in turn give birth 

 to a third generation of females and in this 

 manner a large number of successive gen- 

 erations are produced, in none of which 



