PLANT LICE. 



371 



most, the seventeen -year locust {Cicada septemdecim Linn., 

 Fig. 336) lives over sixteen years as a larva, finishing its 

 transformations on the seventeenth ; there is also, accord- 

 ing to Riley, a thirteen-year variety of this species. 



Fig. .337.— Spittle insect, 

 its natural size. 



a, larva, enlarged ; 



Pig. 3,38.— Cochineal insect, 

 mate ; female natural size and 

 enlarged. 



The froth insect {Ptyelus lineatus, Fig. 337) abounds on 

 grass in early summer. The cochineal insect [Coccus cacti) 

 belongs to the CoccidcB, or bark-lice ; the dried female is 

 used as a dyestufE, and abounds in Central America. 



The plant-louse (Fig. 339, Aphis mali Fabr.) is provided 

 with two tubes on the hind-body from which honey-dew 



Fig. 339.— Apple Aphis. Natural size and enlarged. 



drops, which attracts ants, wasps, etc. In summer the 

 plant-lice reproduce asexually, and as there may be nine or 

 ten generations, one virgin aphis may become the parent of 

 millions of children and grand-children. 



