COLEOPTERA. 75 



the same insects 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 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 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 circu- 

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

 atmosphere, producing a greater transpiration from the leaves, ren- 

 ders a large and continued flow of sap necessary to supply the 

 evaporation. For the want of this, or from some other unexplain- 

 ed 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 subse- 

 quently 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 probably deposits its eggs before August has passed. 

 This little beetle, which is only one tenth of an inch in length, was 

 named Scolytus Pyri, the pear-tree Scolytus, by Professor Peck ; 

 it is of a deep brown color, with the antennae and legs rather 

 paler, or of the color of iron-rust. The thorax is short, very 

 convex, rounded and rough before ; the wing-covers are minutely 

 punctured in rows, and slope off very suddenly and obliquely be- 

 hind ; the shanks are widened and flattened towards the end, 

 beset with a few little teeth externally, and end with a short hook ; 

 and the joints of the feet are slender and entire. It is evident 

 that this insect cannot be retained in the genus Scolytus, as defined 

 by modern naturalists ; but the condition of my specimens will 



