g6 GRAPE DISEASE. 
varieties as are subject to them here ; while a few have occasionally 
been found on their own varieties. Secondly, I have successfully — 
transferred the leaf-lice on to the roots, while M. V. Signoret has 
succeeded in obtaining leaf-galls from lice hatched on the roots. 
Thirdly, the winged form obtained by Dr. Shimer from the galls — 
in this country agrees in its characters with those from the roots, 2 
Fourthly, the nodosities on the roots are, as already stated, pe 
fectly analogous to the galls on the leaves, and differ only in just 
such a manner as one would expect from the difference in the 
plant tissues —a view greatly strengthened by the fact that when 
the gall-lice are forced, by their excessive numbers, to settle om 
the tendrils or leaf-stalks, they produce swellings and knots ap- 
proaching more nearly .to those on the roots than to the galls. 
These facts sufficiently attest the identity of the two types, and 
we have here another case of an insect possessing two distinct 
habits.. It is also like many others of its family, polymorphic, 
i. e., it exists in different forms; yet we have to do with but one 
species. a 
Furrer Facrs Resprcrixe Tue Hasrrs or THE Roomisii® - 
form; which, as it moults, becomes tubercled, and more elonge™ 
or pear-shaped, as shown at Figure 129,j. So Be a 
cled individuals remain without wings, while others seem ge : 
destined from the first to acquire wings. The young, "i 3 
taching themselves, become in a measure stationary, and which : 
one very much of young bark-lice. The fine hair-like ag 
in their functions and elasticity are analogous bane shown 
become loosened from the more fleshy rostrum or sheath, Lace 
at Figure 129, j, and are often so firmly inserted 
that the louse, if disturbed from its place, gener 
them. Three of the threads of this tongue are § ie 
spicuous, but there should be from analogy, four. The 5 and their 
the roots seem to be less prolific than those in the galls, am 
eggs if anything are rather larger. These eggs ar? , with the 
bright yellow color, and, on the dark root, are detec or of a dull 
naked eye as readily as the lice, which become darker ae 
orange as they grow older. during the summer 
The insect is found on the roots in all stages 
