XXXV 



GREEN-FLIES, PLANT-LICE, AND 

 PARTHENOGENESIS 



THE minute "green-flies" which attack all kinds of 

 plants, and among which are ranked the hop- 

 louse or hop-blight, the rose aphis or green-fly of rose 

 trees, the woolly blight or aphis of apple trees and pear 

 trees, and the terrible vine-killer the Phylloxera vastatrix 

 form a special group of bug-like insects known as the 

 Aphides. They have soft cylindrical bodies, six legs, 

 sometimes two pairs of transparent wings, sometimes 

 none, and a sharp beak (in some kinds this is one and a 

 half times as long as the body), with which they prick the 

 soft parts of plants, when they suck up the juices which 

 issue from the wound (Fig. 59). There is in the temperate 

 regions of the world a special kind of aphis or plant-louse 

 peculiar to each of many kinds of flowering plants, 

 including most trees. A very complete, illustrated account 

 of the kinds or species of British aphides, amounting to 

 some two hundred, was produced by the late Mr. Buckton, 

 F.R.S., and published by the Ray Society. 



There are many facts of extraordinary interest about 

 these tiny swarming insects. In the first place, they are 

 closely related to the minute scale-insects or Coccidce, 

 several species of which produce the celebrated lac of 

 lacquer-work and the dyes known as lake, cochineal, and 



