' 860 [Assembly 
frequent occurrence that it has probably been observed by many 
of my readers. About fifteen years ago I first noticed a tree upon 
my farm which was severely affected by this disease, and which 
has continued to suffer from it annually down to the present time. 
Within two rods of this tree are two others which have remained 
wholly unaffected, and have regularly produced a fair yield of 
fruit, whilst not a single nut has been matured upon the diseased 
tree. The excrescences upon the limbs at the time of gathering 
the iruit in autumn, which was the only time I had heretofore 
noticed them, are black, ragged, leathery and cup-shaped, having 
a marked resemblance to some of the species of fungi of the genera 
Peziza, Cenangium , and their kindred. But whether they really 
were of a vegetable nature or were the work of insects I was un¬ 
able to determine from their appearance at that period of the year. 
Mr. T. B Ashton having recently informed me that he had al- 
ways met with the Elegant weeVil [Conotrachelus elegans Say), 
a species most nearly related to the Plum weevil (C. Nenuphar 
Herbst), exclusively upon these diseased hickory trees, although 
I had myself captured it upon butternut, hazlenut and other foli¬ 
age, I resolved the present year to investigate these excrescences 
at the commencement of their growth, and ascertain their cause, 
not knowing but it might throw some light upon the mooted 
origin of the black knots upon the plum and cherry. I have been 
successful in this examination, and have ascertained that although 
these excrescences are of insect origin, the weevil alluded to has 
ncP direct conection with them, and if it really is more common 
upon these diseased walnut trees than elsewhere, as Mr. Ashton’s 
observations indicate, it is only because, like many other insects, it 
prefers diseased and weakened vegetation to that which is healthy 
and of rank vigorous growth. 
The insect which forms these excrescences is a female plant- 
louse, and her proceedings and the effect which they produefi is 
truly wonderful. Hatching probably from eggs that were laid 
the preceding autumn, each individual, early in the season, sta¬ 
tions herself at a particular spot,-either upon the mid-vein of one 
of the leafets, upon the leafstalk, or still farther down, upon the 
green succulent twig which is the growth of the present year. 
