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- 

 lytuSf as now defined, because in this genus the antennae 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 

 latter, 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 

 large and continued flow of sap necessary to supply the evaporation. 

 For the want of this, or from some other unexplained cause, the 

 whole of tlie limb above the seal of ilie 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 



