86 DR. HARRIS’S REPORT. April, 
the eighth, ninth and tenth are united into a knob ; the palpi or fee- 
lers are conical. ‘These insects cannot be retained in the genus Sco- 
lytus, as now defined, because in this genus the antenne have the 
club composed of only two joints. Not having seen these insects in 
a living and entire state, I cannot certainly determine from my speci- 
mens, or from Prof. Peck’s description and figures of them, to which 
of the modern genera they belong. 
For many years past the pear-tree has been found to be subject 
to a peculiar malady, which shows itself during midsummer by the 
sudden withering of the leaves and fruit, and the discoloration of the 
bark of one or more of the limbs, followed by the immediate death 
of the part affected. In June, 1816, the Hon. John Lowell, of 
Roxbury, discovered a minute insect in one of the affected limbs of 
a pear-tree ; since that time he has repeatedly detected the same in- 
sects in blasted limbs, and his discoveries have been confirmed by 
Mr. Henry Wheeler and the late Dr. Oliver Fiske, of Worcester. 
Mr. Lowell submitted the limb and the insect contained in it to the 
examination of Prof. Peck, who gave an account and figure of the 
Jatter, in the fourth volume of the Massachusetts Agricultural Re- 
pository and Journal. From this account, and from a subsequent 
communication by Mr. Lowell, in the fifth volume of the New Eng- 
land Farmer, it appears that the grub or larva of the insect eats its 
way inward through the alburnum or sap-wood into the hardest part 
of the wood, beginning at the root of a bud, behind which probably 
the egg was deposited, following the course of the eye of the bud 
towards the pith, around which it passes, and part of which it also 
consumes ; thus forming, after penetrating through the alburnum, a 
circular burrow or passage in the heart-wood, contiguous to the 
pith which it surrounds. By this means the central vessels, or those 
which convey the ascending sap, are divided, and the circulation is 
cut off. This takes place when the increasing heat of the atmo- 
sphere, producing a greater transpiration from the leaves, renders a 
Jarge and continued flow of sap necessary to supply the evaporation. 
For the want of this, or from some other unexplained cause, the 
whole of the limb above the seat of the insect’s operations suddenly 
withers, and perishes during the intense heat of midsummer. The 
larva is changed to a pupa, and subsequently to a little beetle in the 
