74 INSECTS INJURIOUS TO VEGETATION. 



laid. The grubs hatched from these proceed in feeding nearly at 

 right angles, forming on each side numerous jsarallel furrows, 

 smaller than the central tube of the female. They complete their 

 transformations in October, and eat their way through the bark, 

 which will then be seen to be perforated with thousands of little 

 round holes, through which the beetles have escaped. 



Under the bark of the pitch-pine I have found, in company 

 with the pine bark- beetle, a more slender bark-beetle, of a 

 dark chestnut-brown color, clothed with a few short yellowish 

 hairs, with a long, almost egg-shaped thorax, which is very rough 

 before, and short wing-covers, deeply punctured in rows, hol- 

 lowed out at the tip like a gouge, and beset around the outer edge 

 of the hollow with six little teeth on each side. This beetle 

 measures one fifth of an inch, or rather inore, in length. It 

 arrives at maturity in the autumn, but does not come out of the 

 bark till the following spring, at which time it lays its eggs. It is 

 the Tomicus exesus^ or excavated Tomicus ; the specific name, 

 signifying eaten out or excavated, was given to it by Mr. Say on 

 account of the hollowed and bitten appearance of the end of its 

 wing-covers. Its grubs eat zigzag and wavy passages, parallel to 

 each other, between the bark and the wood. They are much less 

 common in the New England than in the Middle and Southern 

 States, where they abound in the yellow pines. 



Another bark-beetle is found here, closely resembling the pre- 

 ceding, from which it differs chiefly in the inferiority of its size, 

 being but three twentieths of an inch in length, and in having only 

 three or four teeth at the outer extremity of each wing-cover. It 

 is the Tomicus Pini of Mr. Say. The grubs of this insect are 

 very injurious to pine-trees. I have found them under the bark 

 of the white and pitch pine, and they have also been discovered 

 in the larch. The beetles appear during the month of August. 



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 ; after ards he repeatedly detected 



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