THE ELM. 335 
in the centre, a casualty from which young trees are not 
exempt. 
The elm, particularly the English elm, is subject to the 
ravages of several insects. The most fatal of these is the 
scolytus destructor, a small beetle, only about a fourth of an inch 
in length, which perforates the bark of large trees during the 
heat of summer, commonly about the month of July. It 
forms a channel, generally upwards, between the inner bark and 
the wood, into which the female insect deposits her eggs to 
the extent of from twenty to fifty. About the month of Sep- 
tember the larve are hatched ; these ramify, forming horizon- 
tal channels on each side of the original perforation, which is 
commonly an inch or two in length. The caterpillars feed on 
the inner bark, rendered congenial by the descending sap in 
autumn. When the insect finishes its course of feeding, it 
stops in its progress and turns to a pupa, then to a beetle. It 
then gnaws its way straight through the bark, and emerges 
early in summer. The bark of the tree presents the appear- 
ance of being pierced by shot. The circulation of the sap is 
interrupted ; the foliage becomes scanty, and of a sickly hue, 
which is followed by numerous dead branches, and sometimes 
by the death of the whole tree. No practical cure has been dis- 
covered. In Scotland, the effects of the scolytus are seldom 
observed, but in England and on the Continent, and most 
frequently where trees ornament populous towns and frequented 
promenades, the ravages of the insect are most fatal, and very 
likely owing to the absence of the numerous birds which in 
forests and rural districts are sustained by such insects. 
U. montana (Bauhin) : The Mountain, Scotch, or Wych Elm. 
—This species is a native of Scotland, and very valuable as a 
timber tree. It grows to a less height than the English elm. 
Compared with the best varieties of that tree, it is of slower 
growth, yields a much shorter bole, but is far more spreading 
in its habit, more bold in its ramification, and more picturesque 
in figure, more hardy in constitution, and better adapted to 
adorn the glens and mountain sides which it is destined to 
occupy. It usually attains to the height.of about fifty feet, 
