NX 
MEMBRANE-WINGED INSECTS. 27t 
plants and trees, depositing therein their eggs. They 
moisten these cuts also with an irritating fluid, which 
causes the growth of the tumors called galls. When 
the eggs are hatched, the larvz live on the interior of 
these tumors, just as the larvee of the Nut-weevil, § 435, 
live on the nuts in which they are hatched. It is re- 
markable that the same tree should produce on its dif: 
ferent parts galls of various forms and degrees of hard- 
ness, according to the species by which the eggs are 
deposited. The hardest gall is the common gall-nut of 
commerce, so much used in making ink, and in the proc- 
ess of dying black. This is the product of an oak grow- 
ing in the Levant. It has been found that the famous 
“« Apples of Sodom” are galls of a different consistence 
on the same oak, occasioned by another species of Cy- 
nips, or Gall-fly. While the oak apples, so familiar to 
us, appear on the twigs of the oak, there are also differ- 
ent kinds of galls pro- 
duced on the leaves, 
the catkins or pendent 
flowers, and even on 
the root. Those on 
the root are large and 
woody, and eleven 
hundred larvee have 
<> been found in a single 
one of them. While 
the oak seems to be a 
great favorite of the 
Gall-flies, they infest 
also some other trees 
and shrubs. The gall 
of the wild rose, Fig. 
210, is very beautiful, 
being bright and va- 
riegated in color, and 
covered over with bristles. When cut open we find in 
Fig. 210.—Gall of the Wild Rose. 
