THE APHIDES^ OR PLANT-LICE. 415 



from the damage whicli many of them do to cultivated 

 plants, but also from some peculiarities in their mode 

 of reproduction, which have no parallel amongst in- 

 sects. The Aphides J which constitute the greater por- 

 tion of this tribe, are all of small size, but with a rather 

 thick body and furnished with six long legs, upon 

 which they crawl sluggishly about from place to place 

 on the plant infested by them. They are generally 

 found in vast numbers together, upon the growing 

 parts of the plant, on which they sit with their beaks 

 buried in its substance, and the juice which they 

 abstract in this way is frequently so large in quantity 

 as to cause the complete destruction of the plant, or 

 at all events a great reduction in its productiveness. 

 One of the most remarkable instances of the influence 

 of these apparently contemptible agents upon our 

 vegetable productions is presented by the Hop, which, 

 as is well known, is very liable to be infested by a 

 peculiar species of Aphis [A. Humuli), commonly 

 called the Hop-fly. Small as this insect is, it has the 

 greatest influence upon the amount of the crop of 

 Hops, its appearance in great numbers invariably 

 causing a corresponding deficiency in the produce of 

 the plants which it attacks; and it is undoubtedly 

 to the Aphis principally that we must attribute the 

 great variation in the yield of the hop- grounds, a va- 

 riation the amount of which is indicated by the fact, 

 that in some years as much as £470,000 has been paid 

 for duty upon the crops, whilst in others the amount 

 has dwindled down to little more than £15,000. 



Besides living, as most of these insects do, upon the 

 young juicy twigs of plants, a good many of them 

 attack the leaves and produce gall-like excrescences 

 of various kinds, in the interior of which the whole 



