CHAP. Cl.

[7Xma 5 cea:. c/'lmus.

1387

segments bearing two rows of spines directed backwards. Before the larvabecomes a pupa, it spins a strong web, intermixed with particles of wood,which constitutes its cocoon (5); in some instances the larva changes to a pupaunder ground. In jig. 1233., e, f, g, h, and i are representations magnifiedof the spines upon certain of the abdominal segments : e represents the 4thabdominal segment seen laterally ;/, three of the basal row of spines ; g, threeof the hinder row of spines ; and h, three of the basalrow of spines of the 9th abdominal segment. Fig.

1234. represents the jaws, or mandibles, of the larva,with which it cuts its way through the wood : in thisfigure, a is the mandible; b is the labrum, or upperlip; and c shows the clypeus. These mandibles areformidable-looking instruments, each having the ap-pearance of a sort of chisel, with a toothed edge. The perfect insect (d in Jig.1233.) has dark grey wings, clouded with dark brown, and streaked with black.The imago belongs to the class of insects that fly by night, and it appears aboutthe end of June. The female lays but one course of eggs, but these generallyamount to 1000 in number, and are always deposited at the base of the trees;whence the caterpillars penetrate the bark, wherever they can find the easiestentrance. The eggs are small, in proportion to the size of the imago; and thecaterpillar, which grows to a large size, is said to remain in the larva state threeyears. The large size of the larva, Samouelle observes, compared with the small-ness of the egg, strengthens this idea, and prepares us to expect that it would belikely to consume a great quantity of wood in the progress of its growth. Thesmell of the larva is so strong, as to be easily perceived by persons passing neartrees infested with it. ( Samouelle. ) The green woodpecker preys upon thesecaterpillars, and its stomach, on dissection, has an intolerable stench. The prin-cipal kinds of tree which the cossus feeds on are, the elm, the alder, the oak, theash, the walnut, the beech, the lime, and some kinds of willow and poplar.The larva; devour the liber, or inner bark, making long galleries in thewood, like the insects that attack the pear tree (see p. 886.), and finallydestroying the tree. Many remedies have been proposed ; but that of Latreilleappears to be most approved of in France . This consists in surrounding thebase of the tree, where it has been observed that the females always deposittheir eggs, with a thick coating of a mixture of clay and cow-dung, which theinsects cannot penetrate. For further inform-ation respecting this insect, see Gard. Mag.,vol. xii. p. 464. The fourth enemy of the elmtree is the scolytus. The S. destructor Oliv.is generally considered by far the most inju-rious ; but it is assisted in its ravages byanother species, the S. armatus.

Scolytus destructor. The female insect(Jig. 1235., in which a is the natural size,and d the insect magnified), about July, boresthrough the bark, until she has reached thepoint between the soft wood and the innerbark; she then forms in the latter a verticalchannel, usually upwards, of about 2 in. inength, on each side of which she deposits hereggs as she advances, to the number of from 20jo 50 in all. It appears probable that, after do-ing this, she dies, without making her way outa gain, as she may be often found dead at thef n of the channel. About September, thearv® are hatched; and they commence feed-ing upon the matter of the inner bark (c), ats^ht if the channel (b), and, in a veryg degree, on that of the soft wood opposite ; advancing, as they feed, in a