HEMIPTERA. 
r6l 
the vine. Carbon bisulphide has been used to some extent 
for this purpose. 
Where the vineyards are so situated that they can be 
submerged for a period of at least forty days during the 
winter, the insect can be drowned. But this method is 
obviously of limited application. 
It is found that vines growing in very sandy soil resist 
the attacks of the Grape Phylloxera. This is supposed to be 
due to the difficulty experienced by the insect in finding 
passage through such soil. 
Another well-known example of the plant-lice that make 
galls is Colopha ulmicola (Col'o-pha ul-mic'o-la), which makes 
the Cockscomb Elm-gall. This gall is shaped more or less 
like a cock’s comb, and is very common on the upper side of 
the leaves of the elm. 
There is a group of species of plant-lice known as the 
Woolly Aphids, on account of a white more or less downy 
or waxy substance with which the bodies of these insects are 
covered. Large numbers of one of these species are often 
found crowded together on the under side of the branches of 
alder. This species is known as the Alder-blight, Schizoneura 
tessellata (Schiz-o-neu'ra tes-sel-la'ta). In addition to the 
white excretion with which the body is covered this insect 
excretes large quantities of honey-dew. The result is that 
the branches infested by this insect, and those beneath the 
clusters of Aphids, become blackened with fungi that grow 
upon this secretion. There is also a curious fungus which 
grows in large spongy masses immediately beneath the clus¬ 
ters of plant-lice; this is known to botanists as Scorias 
spongiosum. It is evidently fed by the honey-dew that falls 
upon it. 
The Beech-tree Blight, Schizoneura imbricator (im-bri- 
ca'tor), infests both the twigs and leaves of beech. Like 
the preceding species it occurs in clusters of individuals, 
each of which is clothed with a conspicuous downy excre¬ 
tion. These clusters often attract attention by the curious 
13 
