FOOD PLANTS. 
37 
develop in the fruit on the trees, and wormy ripe cherries are vers' 
generally present on the trees, and on the market. (See PL XI.) 
There remains to be mentioned more particularly the recorded use, 
for egg-laying purposes and as food for larvae, of the so-called black- 
knot of cherries and plums. (See fig. 19.) Prof. W. D. Peck, in the 
Massachusetts Agricultural Repository (vol. 5, p. 312, 1819), records 
rearing of the beetles from grubs found in the warty excrescences of a 
cherry tree, for which reason he gave it the name of RhjncJisenus 
cerasi, or the cherry weevil. Grubs apparently the same as those 
found in the plums are stated to have been frequently observed in 
Fig. 19.— Black-knot of plum, showing, on the left, infestation by plum-curculio larva 1 . (Original.) 
the warts, which it was then thought were caused by this insect. 
The larvse observed by Prof. Peck went into the ground July 6 and 
on the 30th of the month the beetles began to appear. A resume of 
Prof. Peck's observations on the curculio are given by Harris, who 
recommends that the excrescences of plum and cherry trees be cut 
out each year after the last of June. He adds that the moose plum 
(Prunus americana) seems to escape the attack of the insect, for no 
warts are found upon it even when growing in the immediate vicinity 
of diseased foreign trees. In his Essay Dr. Fitch, in commenting 
