124 Mr W. S. Macleay on ike State of the Elm Trees 
becomes increased beyond its due limit, we must either apply 
the axe without scruple to the seat of the disease, or make up 
our minds to submit to the utter destruction of our plantations. 
Almost all timber-eating insects are comprised in three orders, 
\iz. Coleoptera, or beetles; Lepidoptera , or moths, butterflies, 
&c. ; and Hymenoptera , or bees, wasps, &c. All these in their 
youngest state are worms or larvae, and it is while in this stage 
of their life that they commit the direct injury to the trees, 
either by gnawing off* the bark, or by devouring the wood. The 
communication of the disease to other trees is periodical ; for 
when the above mentioned worms or larvae arrive at their per- 
fect and winged state, the mischief committed by them directly 
is comparatively trifling, and, in fact, generally results, not so 
much from their voracity, as from their attempts to extricate 
themselves, and to arrive at the external air, or from their en- 
deavours to commit their eggs to a proper nidus. But as thev 
are now winged, and capable of depositing myriads of eggs, the 
germs of as many devouring larvae, the disease is thus dispersed 
throughout the neighbourhood of the tree originally infected. 
If, however, it be, in this their perfect state, that the insects are 
most formidable, having attained the power of propagating the 
disease, it is also from an accurate knowledge of them while in 
this state, that we can alone derive any hope of being able to 
counteract their mischief. 
The first thing, indeed, to be done in all such cases is, to as- 
certain the species of perfect insect, which occasions the disease. 
The experienced naturalist is able from this examination of the 
worm or larva which he finds devouring the wood, not only to 
ascertain the order and family, but often the genus, and even 
the species of winged insect which has produced it; and having 
determined the genus or species, it becomes an easy matter to 
know the season of its appearance. None of these timber-eating 
insects remain in their perfect or winged state throughout the 
year, and rarely for more than eight weeks. We may therefore 
easily ascertain the proper time for cutting down those trees 
which are so much infected with larvae as to afford no hope of 
saving them ; for it would obviously be the height of impru- 
dence not to seize the only opportunity of preventing the annual 
