io8 Hemiptera-Homoptera. 



ities. In the spring there are produced, from eggs laid 

 the previous autumn, wingless individuals. These are 

 all of the same form (sex), and give birth to living 

 young. The second and succeeding generations are like 

 the first, until in the early autumn when there is pro- 

 duced a brood of winged individuals. This brood con- 

 sists of both males and females. These pair; the 

 males then die, the females lay eggs after which they 

 die. The eggs hatch in the following spring, and pro- 

 duce the agamic wingless form. 



The species of Aphis infest both the foliage and the 

 roots of plants. 



Ants and Aphides (5, I., no; 7, 335). 



The principal enemies of the plant lice are Ichneu- 

 mon-flies, Syrphus-flies, " Lady-birds," and the Aphis- 

 lions (Chrysopa). 



Remedies. — Tobacco smoke. Strong soap-suds. 



Many members of this family produce galls. The 

 following species is the most noted example, and will 

 serve to illustrate the habits of the gall-making spe- 

 cies : — 



The Grape Phylloxera, Phylloxera vastatrix Planch- 

 on. — Two constant types : One, called galheeola by 

 Riley, lives in galls on the leaves. This form was de- 

 scribed, by. Dr. Asa Fitch, under the name of Pem- 

 phigus vitifoliae. (4, I., 158 ; 4, III., 397). The other 

 form is called radicicola, by Riley, and infests swell- 

 ings of the roots. 



Type Gallcecola or Gall-inhabiting. — This type oc- 

 curs only as an agamic, wingless female. 



Note manner of development of the young lice, and 

 of the galls. 



