PLANT LICE. 149 
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 let- 
tuce 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 
Fic. 138—Sensory pits of peach louse; Fic. 138a—a, Antenna of melon plant 
a, antenna of young lice; b, first louse showing sensory pits; b, beak 
long joint of winged form; c, sec- ofsame. After Smidt. 
ond long joint; d, third long joint; 
e, whip joint; f,; sensory pit of an- 
tenna, from top; g, same from 
side. After Smidt. 
grape-vines, usually cause the death of the vine. This same in- 
sect, which produces galls on the roots of the vines, can also 
produce small galls on the under side of the leaf. These leaf- 
galls are hollow and serve as houses for the lice. The woolly 
louse of the apples is a species which is becoming more and 
more important and destructive with the development of our 
apple-orchards. They collect in clusters, which become very con- 
