STATE AGRICULTURAL SOCIETY. 
361 
PLUM. LIMBS. 
and of a triangular shape, resembling that of a beech nut, and of 
a uniform pale green color without any spots or stripes. Like 
other tree hoppers (which name I apply to insects of the family 
Membracida ) and leaf hoppers ( Tettigoniida ) these insects when 
approached by the finger give a sudden strong leap and become 
lost to the view. 
I am indebted to George Clark, Esq., of East Springfield, Otsego 
county, for the above information respecting the work of an insect, 
which, from his description of it, will be the species which I have 
named; but specimens which were sent to Dr. Harris a few years 
since, were said to be the Ceresa bubalus (See No. 22) in a letter 
from him, published at that time in the Journal N. Y. State Ag. 
Society. Mr. C. informs me the insect he alludes to has no pro¬ 
jecting points resembling horns, anteriorly, and is of a uniform pale 
or pea green color, destitute of any spots or marks, whereas the 
bubalus when alive is deeper green, freckled with whitish dots, 
and has a pale yellow streak from the horn backwards along each 
side. The bubalus , however, is closely related to this insect and 
is common upon the fruit and other trees in our yards, and both 
these species it is probable cut the bark of the plum and other 
trees in the manner stated above, and we presume the plum 
weevil also makes a curved incision in the limbs of the plum 
similar to those we have noticed in the pear. 
Mr. Clark has for several years given particular attention to the 
slits which this tree hopper makes in the bark of the plum and is 
confident these wounds are the foundation of that most fatal malady 
the “ Black knot.” The examinations of this disease which I have 
made have convinced me that the different insects which writers 
in our agricultural periodicals have pointed out as producing these 
excrescences are species which are wholly innocent of the orime 
laid to their charge. I have watched the growth of the excres¬ 
cences from their first commencement to their full development, 
without being able to detect the least indication of an insect in 
some of them, and - in other instances where insects have been 
present it was plain they were there as a consequence and not as 
a cause of the disease. The fact, however, that tree hoppers and 
the plum weevil make incisions in the bark at the same place 
where this disease shows itself, calls for future investigations, to 
