COMMON PEAR-TREE. 293 
this means, the central vessels, or those which convey the ascending sap, are 
divided, and the circulation cnt 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 Irom some other unknown cause, the whole of the branch above 
the perforated part, suddenly withers and perishes, during the intense heat of the 
season. The larvae, which are changed to pupae, and subsequently to little bee- 
tles, in the bottom of their burrows, make their escape from the tree in tbe latter 
part of June, or the beginning of July, and probably deposit their eggs before the 
end of August. These beetles are about one tenth of an inch in length, are of a 
deep-brown colour, with their antennae and legs rather pale, or of the colour of 
iron rust. The remedy suggested by Mr. Lowell and Professor Peck, to prevent 
other branches and trees from being subsequently attacked in the same way, con- 
sists in cutting off the blasted limb below the seat of injury, and burning it before 
the perfect insect has made its escape. It will therefore be necessary, carefully 
to examine the trees daily, during the month of June, and watch for the first 
indication of disease ; otherwise the remedy will be applied too late to prevent 
the dispersion of the insects among other trees.* 
The pear-tree is also perforated by a species of borer, (JEgeria pyri, Harris,) 
which lives under the bark of the trunk, where, towards the end of summer, it 
forms its cocoon. The perfect insect appears in autumn, and like all its conge- 
ners, leaves its chrysalis skin projecting from the orifice of the burrow which it 
has previously made. Its wings expand rather more than half an inch, are 
transparent, but veined, bordered and fringed with purplish-black, and across 
the tips of the fore-wings is a broad, dark band, glossed with coppery tints. The 
prevailing colour of the upper side of the body is purple-black ; but most of the 
under side is golden-yellow, as are the edges of the collar of the shoulder-covers, 
and of the fan-shaped brush on the tail ; and there is a broad yellow band across 
the middle of the abdomen, preceded by two narrow bands of the same colour, f 
Among other insects that infest the pear-tree, may be mentioned the pigeon 
tremex, {Tremex columba, Harris,) described under the head of " Insects, &c.," in 
our article on the Ulmus americana ; also a species of bark-louse, {Coccus ***#*) 
occurring in considerable numbers, in two different forms and sizes, and adhere to 
the bark of the trees in autumn, and during the winter, in a dormant state. 
Those of the largest size are less than a tenth of an inch in length, and resemble 
in their form the common oyster-shell, being broad at the posterior end, and 
tapering towards the other, which is surmounted by a little oval, brownish scale. 
The small ones, which are about half of the length of the large ones, are of a 
very long oval shape, or almost four-sided, rounded at the ends, with one extrem- 
ity covered by a minute,, oval, dark-coloured scale. For a description of the 
general habits of the genus coccus, the reader is referred to the remarks under the 
head of "Insects," in our article on the orange. 
The leaves of the pear-tree are particularly subject to the attacks of the gold- 
smith beetle, (Areoda lanigera, Harris,) and the larva? of the slug-fly, (Ble/uio- 
campa cerasi,) the latter of which is described under the head of "Accidents, 
&c.," in our article on the common cherry-tree. 
Properties and Uses. The wood of the common pear-tree is heavy, strong, 
compact, of a fine grain, and slightly tinged with red. In common with that of 
all the Rosaceae, it is liable to have its natural colour changed by steeping in 
water, which, therefore, ought to be avoided, when intended for particular pur- 
poses in the arts. When green, it weighs nearly eighty pounds to a cubic foot 
and from forty-nine to fifty-three pounds, when dry. According to l)u Ham el, 
* See Hams' Report on the Insects of Massachusetts, pp. 75, 76. f Ibi(1 - P- 235 - 
