120 
In the case of most of our native plant-lice, winged forms 
are produced in the autumn to enable the female to deposit the 
winter-eggs (Fig. 62, Plate 14), ina suitably protected place. 
Winged lice seem to spring from the earth just before the leaves 
fall from the trees, and sometimes they are numerous enough to 
form clouds. During the summer most species of lice possess 
no wings, all are females, and reproduce without the interven- 
tion of the male. This is carried on for a great many genera- 
tions, but in the life-history of each species there is a time in 
which both sexes appear and mate. During the summer lice 
reproduce by budding, and not in the usual way. Lice that 
possess wings are notnecessarily sexual insects; in many cases 
such winged insects are simply ‘‘nurses”, which deposit living 
young upon trees not so badly infested as the ones they left. 
The presence of plant-lice is made manifest in various ways. 
Sometimes the plant is sapped of its vitality and dies, or is 
impoverished simply by loss of its sap. At other times an 
abnormal growth is produced in the leaf or stem on which the 
louse feeds. In the case of the currant-louse (Fig. 42, Plate 8), 
as well as in that of the plum-louse, the twisted and bladder-like 
leaves present a shelter in which the young lice can be raised in 
safety. Atother timesagain theabnormal growth extends to the 
formation of a hollow gall, in which the family of lice live very 
much asinasmallhouse. Our cottonwood trees produce a famil- 
iar example in the form of large terminal galls; such galls are 
always open to allow for the exit of their inmates. Fig. 63, 
Plate 8, shows a common gall on the elm, called the cockscomb 
gall from its fancied resemblance to the comb of a fowl. At 
other times plant-lice work on the roots of plants, as in the 
case of our lettuce root louse, and the grape-phylloxera. In 
the latter case large knobs and gall-like swellings are produced 
by the sucking lice, and here they may be found. The lice, if 
infesting european grape-vines, usually cause the death of the 
vine. This same insect, which produces galls on the roots of 
the vines, can also produce small galls on the under side of the 
leaves; these leaf-galls are hollow and serve as houses for the 
lice. The wocly louse of the apples is a species which is becom- 
ing more and more important and destructive with the develop- 
ment ofourapple orchards. They collect in clusters, which be- 
come very conspicuous, because the louse is covered with a 
