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 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 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 voung 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 Psylla , 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. 
