THE BLIGHT-BEETLE. 89 



followed by the immediate death of the part affected. This 

 kind of blight, as it has been called, being oftenest confined 

 to a smgle branch, or to the extremity of a branch, seems to 

 be a local affection only. It ends with the death of the 

 branch, down to a certain point, but does not extend below 

 the seat of attack, and does not aflPect the health of other 

 parts of the tree. In June, 1816, the Hon. John Lowell, of 

 Roxbury, discovered a minute insect in one of the affected 

 limbs of a pear-tree ; afterwards, he repeatedly detected the 

 same insects in blasted limbs, and his discoveries have been 

 confirmed by Mr. Henry Wheeler and the late Dr. Oliver 

 Fiske, of Worcester, and by many other persons. Mr. Low- 

 ell submitted the limb and the insect contained therein to 

 the examination of Professor Peck, who gave an account 

 and figure of the latter, in the fourth volume of the " Massa- 

 chusetts Agricultural Repository and Journal." 



From this account, and from the subsequent communica- 

 tion 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 circula- 

 tion is cut off. This takes place when the increasing heat of 

 the atmosphere, producing a greater transpiration fi-om the 

 leaves, renders a large and continued flow of sap necessary 

 to supply the evaporation. For the want of this, or fi-om 

 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 



12 



