16 
Their normal method of passing the winter appears to be in the 
egg state, but this is by no means the universal rule, as the same 
species is sometimes found both in the egg and larva state during the 
winter, resembling in this respect some true Apliidians. There are 
usually several broods during the summer all produced from eggs de¬ 
posited by the female after fertilization by the male, agamic generation 
being apparently unknown in this family. But all the females which 
deposit eggs do not acquire wings. According to Macquart the eggs 
deposited in the summer hatch in eight or ten days, soon after which 
(in the case of the Psylla of the larch) the young larvae disperse upon 
the foliage. 
The species of this genus are somewhat numerous, and, as in 
Aphis , are usually named after the plant upon which they reside — 
entomologists taking it for granted that as a rule, a Psylla or an 
Aphis will be found on but one species of plant. 
5. Psylla pyri. The Jumping Plant-louse of the Pear-tree. (Fig. 2.J 
This species has the head but moderately cleft in front, and pr# 
duces two if .not more broods during the summer. The young are 
not covered with a cottony substance, but are naked. 
The following history of its operations, derived chiefly from Harris 
Kollar and others, will, with the description given below, enable th< 
orchardist to detect it whenever it invades the premises : 
It infests pear trees, to which its operations appear to be almos' 
exclusively confined, and is found on these, in some of its forms, fron 
May to October in the northern sections, and from April to Novembei 
in the southern sections, and is probably two or three-brooded, varying 
somewhat according to latitude. According to Kollar, the Luropeai 
Pear-tree Psylla (which is the same as our species, it being imported 
comes forth from its winter retreat, provided with wings, as soon ai 
the buds of the fruit trees begin to expand. After pairing, the female 
lays her eggs in great numbers, near each other, on the young leaves 
and blossoms, or on the newly formed shoots. 
The eggs are oblong, yellowish, and look somewhat like grains o 
pollen. The young insects, soon after they are hatched, resembL 
young, wingless plant-lice (true Aphides,) and are of a dark yellov 
color. They change their skins and color repeatedly, and acquire wing 
scales or rudimentary wings; then fix themselves to the bark in rows 
and remain sucking the sap until about to undergo their last change 
when they disperse among the leaves, cast off their skins and appea 
in their winged form. 
While Kollar is doubtless generally correct in reference to the histor; 
of this species, his statement in reference to the eggs and the metho< 
of hibernating must be received with some caution. Leon Defour, ii 
his admirable “Researches upon the Anatomy and Physiology o 
Hemipterous Insects,” speaking of the Psylla of the fig {Psylla ficus) 
a closely allied species, remarks that he dissected, at the end o 
October, a female far advanced in gestation, thereby ascertaining th 
character of the eggs, which are peculiar. That in November h 
hunted the leaves and summits of the plants on which these insect 
