COLEOPTERA. "79 



the Hon. John Lowell, of Roxbury, discovered a minute insect 

 in one of the affected limbs of a pear-tree ; afterwards, he re- 

 peatedly detected the same insects in blasted limbs, and his 

 discoveries have been confirmed by INIr. Henry Wheeler and 

 the late Dr. Oliver Fiske, of Worcester, and by many other 

 persons. Mr. Lowell submitted the limb and the insect con- 

 tained therein to the examination of Professor Peck, who gave 

 an account and figure of the latter, in the fourth volume of the 

 " Massachusetts Agricultural Repository and Journal." From 

 this account, and from the subsequent communication by Mr. 

 Lowell, in the fifth volume of the " New England Farmer,"' it 

 appears that the grub or larva of the insect eats its way inward 

 through the albvirnum 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 com'se 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 atmosphere, 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 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 bottom of its burrow, makes its escape from the 

 tree in the latter part of June, or beginning of July, and pro- 

 bably deposits its eggs before August has passed. This insect, 

 which may be called the blig-ht-beetle, from the injury it occa- 

 sions, attacks also apple, apricot, and plum trees, though less 

 frequently than pear-trees. In the latter part of May, 1843, a 

 piece of the blighted hmb of an apple-tree was sent to me for 

 examination. It was twenty eight inches in length, and three 

 quarters of an inch in diameter at the lower end. Its surface 

 bore the marks of twenty buds, thirteen of which were perfo- 



