HEMIPTERA. 187 



their eggs,, and the wounds thus made sometimes produce Uttle 

 excrescences or swelHngs on the plant. These leaping plant-lice 

 belong to a genus called Psylla, which was the Greek name for a 

 small jumping insect. They are by no means so prolific as the 

 other plant-lice, for 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 they im- 

 bibe through their tubular beaks. The young 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. 



Others, both sexes of which are also winged, have long and 

 slender bodies, very narrow wings, which are fringed with fine 

 hairs, and lie flatly on the back when not in use. They are ex- 

 ceedingly active in all their motions, and seem to leap rather than 

 fly. They live on leaves, flowers, in buds, and even in the 

 crevices of the bark of plants, but are so small that they readily 

 escape notice, the largest being not more than one tenth of an 

 inch in length. These minute and slender insects belong to the 

 genus Tlirips. Their punctures appear to poison plants, and 

 often produce deformities in the leaves and blossoms. The 

 peach-tree sometimes suffers severely from their attacks, as well as 

 from those of the true plant-lice ; and they are found beneath the 

 leaves, in little hollows caused by their irritating punctures. The 

 same applications that are employed for the destruction of plant- 

 lice may be used with advantage upon plants infested with the 

 Thrips. 



Aphides^ or plant-lice, as they are usually called, are among 

 the most extraordinary of insects. They are found upon almost 

 all parts of plants, the roots, stems, young shoots, buds, and 

 leaves, and there is scarcely a plant which does not harbour one or 

 two kinds peculiar to itself. They are, moreover, exceedingly 

 prolific, for Reaumur has proved that one individual, in five gen- 

 erations, may become the progenitor of nearly six thousand mil- 

 Jions of descendants. It often happens that the succulent ex- 

 tremities and stems of plants will, in an incredibly short space of 

 time, become completely coated with a living mass of these little 

 lice. These are usually wingless, consisting of the young and of 



