HEMIPTERA. 201 



tenth, but less than three twentieths of an inch. It may be 

 called Tctfig-onia Fabcc. Probably it passes the winter in the 

 same way as the vine-hopper. 



2. Pr-ANT-LicE. (Aphididcc.) 



The Aphidians, in which gronp we include the insects 

 commonly known by the name of plant-lice, difi'er remarkably 

 from all the foregoing in their appearance, their formation, 

 and their manner of increase. Their bodies are very soft, and 

 usually more or less oval. The females are often without 

 wing-covers and wings; and the former, when they exist, do 

 not differ in texture from the wings, but are usually much 

 larger and more useful in flight. We may therefore cease to 

 call these parts wing-covers, in all the remaining insects of this 

 order, and apply to them the name of upper wings. 



Some of the Aphidians have the power of leaping, like the 

 leaf-hoppers, from which, however, they differ in having very 

 large and transparent upper wings, which cover the sides of 

 the body like a very steep roof; and their antennoB are pretty 

 long and thread-like, and are tipped with two short bristles at 

 the end. Both sexes, when arrived at maturity, are winged, 

 and some of the females are provided with a kind of awl at 

 the end of the body, very different, however, from the piercers 

 of the foregoing insects. With this they prick the leaves in 

 which they deposit their eggs, and the wounds thus made 

 sometimes produce little excrescences or swellings on the 

 plant. These leaping plant-lice belong to a genus called 

 Psi/lla, which was the Greek name for a small jumping in- 

 sect. They are by no means so prolific as the other plant-lice, 

 for ordinarily they produce only one brood in the year. They 

 live in groups, composed of about a dozen individuals each, 

 upon the stems and leaves of plants, the juices of which the}^ 

 imbibe through their tubular beaks. The yonng are often 

 covered with a substance resembling fine cotton arranged in 

 flakes. This is the case with some which are found on the 

 alder and birch in the spring of the year. 



Within a few years, a kind of Ps//Ila, before unknown here, 

 has appeared upon pear-trees in the western parts of Connecti- 

 • 26 



