PLANT-LICE 



(Family Aphididce.) 



The plant-lice are very numerous not only in point of num- 

 bers of individuals but also of numbers of species. In many 

 respects these insects are abnormal, especially in their method of 

 development, and they have attracted great attention from 

 naturalists since Bonnet discovered, 1 50 years ago, the peculiar 



^=Cf 



Fig. 157. — Nectarophora pisum : the green-pea plant-louse. (After Chittenden.) 



phenomenon known as parthenogenesis, which is almost invari- 

 ably the rule amongst these creatures. Their life history is very 

 surprising and their relations with other insects, especially with 

 ants, are most interesting. They are very destructive insects, 

 preying upon practically all cultivated plants, and their rate of 

 increase is so enormous that if it were not for their innumerable 



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