38 THE PLUM CURCULIO. 
on the nature of black-knot, states that the larvae of the curculio are 
almost always found in these growths, and the grubs consume nearly 
all the spongy matter of the warts. Later he adds: 
We think the fact well established that this insect breeds in these black-knot excres- 
cences with about the same avidity that it does in young fruit, notwithstanding these 
substances are unlike each other. 
Dr. Fitch expresses the belief that the curculio also resorts to the 
bark of different fruit trees in which to deposit its eggs when it can 
find no young fruits to meet its wants, and cites Melsheimer's (A 
Catalogue of the Insects of Pennsylvania, 1806, p. 28, No. 589) state- 
ment 50 years earlier that the curculio bred in the bark of peach trees 
as well as in the fruit. Dr. Fitch also records finding numerous 
curved incisions in the bark of pear resembling those made by the 
curculio, causing little blister-like elevations, containing from 4 to 
6 minute footless maggots which he thought belonged to the curculio, 
the insect wintering in the larval condition in the bark. In the First 
Missouri Keport Riley states that the curculio deposits and the 
larvae mature in the black-knot of plum, and quotes Dr. Hull to the 
effect that it oviposits in vigorous shoots of peach, but that the larva 
does not mature in these shoots. 
Dr. Trimble says that black-knot, so often found on plum and 
cherry trees, is used freely by the curculio. These knots are often 
several days in advance of the young fruit, and the female curculio 
has been known to exhaust her supply of eggs in them before the 
young cherries or plums on the same trees were full formed. These 
positive statements as to the breeding of the insect in black-knot are 
scarcely to be questioned. 
During the season of 1910 we were able to verify these records. 
From a quantity of fresh black-knot material cut from a European 
variety of plum in full fruit at Bluemont, Va., one beetle was reared. 
Mr. A. G. Hammar, however, at Douglas, Mich., found the curculio 
breeding very abundantly in black-knot on plums and cherries and 
succeeded in rearing many hundreds of adults. (See fig. 19.) The 
comparative scarcity of suitable fruit in the neighborhood was doubt- 
less responsible for the great extent to which black-knot was used by 
the insect. 
Fruits in which the larvse fail to mature. — As already indicated, 
oviposition may occur in numerous fruits which are hardly fitted for 
the future development of the larvae. As will be shown under another 
caption (p. 56), there is a considerable mortality of eggs and larvae in 
all classes of fruit which do not fall to the ground; but in the case of 
pears, and doubtless the grape, huckleberry, persimmon, and similar 
fruits recorded as used for egg laying, the larvae would in most cases 
be unable to mature. This has been shown to be true in the case of 
