PLANT LICE 



no bustle, no commotion, for each insect has its sucking 

 bristles buried in the leaf, and its pump is busy keeping 

 the stomach supplied with liquid food. The aphis crowds 

 are mere herds, not communities or social groups as in 

 the case of the termites, ants, or bees. 



Wherever there are aphids there are ants, and in con- 

 trast to the aphids, the ants are always rushing about all 

 over the place as if they were looking for something and 

 each wanted to be the first to find it. Suddenly one spies 

 a droplet ol some clear liquid lying on the leaf and gob- 

 bles it up, swallowing it so quickly that the spherule 

 seems to vanish by magic, and then the ant is off again 

 in the same excited manner. The explanation of the 

 presence and the actions of the ants among the aphids 

 is this: the sap of the plants furnishes an unbalanced diet, 

 the sugar content being far too great in proportion to the 

 protein. Consequently the aphids eject from their bodies 

 drops of sweet liquid, and it is this liquid, called "honey 

 dew," that the ants search out so eagerly. Some of the 

 ants induce the aphids to give up the honey dew by strok- 

 ing the bodies of the latter. The glistening coat often 

 seen on the leaves of city shade trees and the shiny liquid 

 that bespatters the sidewalks beneath is honey dew dis- 

 charged from innumerable aphids infesting the under sur- 

 faces of the leaves. 



In studying the termites, we learned that it is possible 

 for a single pair of insects to produce regularly several 

 kinds of offspring differing in other ways than those of 

 sex. In the aphids, a somewhat similar thing occurs in 

 that each species may be represented by a number of 

 forms; but with the aphids these different forms con- 

 stitute successive generations. If events took place in 

 a human family as they do in an aphid family, children 

 born of normal parents would grow up to be quite different 

 from either their father or their mother; the children of 

 these children would again be different from their parents 

 and also from their grandparents, and when mature they 



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