CHAP. CI, ULMA‘CE. U’LMUS. 1387 
segments bearing two rows of spines directed backwards. Before the larva 
becomes a pupa, it spins a strong web, intermixed with particles of wood, 
which constitutes its cocoon (4); in some instances the larva changes to a pupa 
under ground. In fig. 1233., e, f, g,h, andiare representations magnified 
of the spines upon certain of the abdominal segments: e represents the 4th 
abdominal segment seen laterally ; f, three of the basal row of spines ; g, three 
of the hinder row of spines ; and 4, three of the basal 
row 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 this 
figure, a is the mandible; 6 is the labrum, or upper 
lip ; and c shows the clypeus. These mandibles are S  iog4 
formidable-looking instruments, each having the ap- nr et 
pearance of a sort of chisel, with a toothed edge. The perfect insect (d in fig. 
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 about 
the end of June. The female lays but one course of eggs, but these generally 
amount 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 easiest 
entrance. The eggs are small, in proportion to the size of the imago; and the 
caterpillar, which grows to a large size, is said to remain in the larva state three 
years. 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 be 
likely to consume a great quantity of wood in the progress of its growth. The 
smell of the larva is so strong, as to be easily perceived by persons passing near 
trees infested with it. (Samouelle.) The green woodpecker preys upon these 
caterpillars, 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, the 
ash, the walnut, the beech, the lime, and some kinds of willow and poplar. 
The larvae devour the liber, or inner bark, making long galleries in the 
wood, like the insects that attack the pear tree (see p. 886.), and finally 
destroying the tree. Many remedies have been proposed ; but that of Latreille 
appears to be most approved of in France. This consists in surrounding the 
base of the tree, where it has been observed that the females always deposit 
their eggs, with a thick coating of a mixture of clay and cow-dung, which the 
insects cannot penetrate. For further inform- 
ation respecting this insect, see Gard. Mag., 
vol, xii. p. 464. The fourth enemy of the elm 
tree is the scolytus. The S. destractor Oliv. 
is generally considered by far the most inju- 
rious; but it is assisted in its ravages by 
another species, the 8. armaAtus. 
Scolytus destrictor. The female insect 
(fig. 1235., in which a is the natural size, 
and d the insect magnified ), about July, bores 
through the bark, until she has reached the 
point between the soft wood and the inner 
bark; she then forms in the latter a vertical 
channel, usually upwards, of about 2 in. in 
length, on each side of which she deposits her 
eggs as she advances, to the number of from 20 
to 50 in all. It appears probable that, after do- 
ing this, she dies, without making her way out 
in, as she may be often found dead at the 
end of the channel. About September, the 
larvae are hatched ; and they commence feed- 
ing upon the matter of the inner bark (c), at 
the edge of the channel (4), and, in a very 
1235 
slight degree, on that of the soft wood opposite ; advancing, as they feed, ina 
