COMMON PEAR-TREE. 293 



this means, the central vessels, or those which convey the ascending sap, are 

 divided, and the circvaation 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 trom some other unknown cause, the wiiole 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 the 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 otf 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, {^geria 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, {Tre?7ie.v colntnba, 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 oiir article on the orange. 



The leaves of the pear-tree are particularly subject to the attacks of the gold- 

 smith beetle, {Ar-eoda latiigera, Harris,) and the larvae of the slug-fly, (^Ble/iiio- 

 ca7npa 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. Wlien green, it weighs nearly eighty pounds to a cubic foot 

 and from forty-nine to fifty-three pounds, when dry. According to Du Hamel, 



* See UaiTis" Report on the Insects of Massachusetts, pp. 75, 76. f Ibid. p. 235. 



