THE LEAPING PLANT-LICE. 231 



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 thev 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 Psylla, which was the Greek name for a small jump- 

 ing insect. 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 they imbibe 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. 



Within a few years, a kind of Psylla, before unknown 

 here, has appeared upon pear-trees in the western parts of 

 Connecticut and of Massachusetts, particularly in the valley 

 of the Housatonic, and in the adjoining counties of Dutchess 

 and Columbia in New York. It was first made known to 

 me, in December, 1848, by Dr. Ovid Plumb, of Salisbury, 

 Connecticut, and it is the subject of a communication in the 

 " American Agriculturist," for January, 1849. Since that 

 time, Dr. Plumb has favored me with additional observa- 

 tions, and an account of his experiments, with various rem- 

 edies, and towards the end of July, 1851, a brief visit to 

 Salisbury gave me an opportunity of seeing the insects in 

 a living condition, and in the midst of their operations 

 upon the trees. 



This Pgylla, or jumping plant-louse, is one of the kinds 

 whose young are naked, or not covered with a coat of cotton. 

 In some of its forms it is found on pear-trees during most 

 of the time from May to October ; and probably two if not 

 more broods are produced in the course of the summer. 



