LETTERS ON ENTOMOLOGY. 23 
the lungs of an ox. Is not this surprising ? It 
is rather singular that the male should partake 
the labour with the female, which in the insect 
world is a very rare occurrence. 
Nothing is more unwholesome than the effluvia 
of decaying vegetable matter, and in removing 
this, our little friends render us an important 
service. It is very curious that stagnant water, 
winch would become putrid without, is made 
sweet and wholesome by the innumerable larvae 
of gnats, ephemera?, and other insects which 
live in it. Linnaeus' s experiment easily proves 
this : if two vessels are filled with putrid water, 
leaving the larva? in one, and taking them out 
of the other, the first will be found pure and 
sweet, and the other will remain in its impure 
state. The wood-destroying insects are highly 
useful in countries overspread with immense 
forests, where lightning and hurricanes make such 
devastation ; yet no traces of the ruin are to be 
found, though some of the gigantic tropical trees 
are almost impervious to the action of the ele- 
ments. They, however, soon disappear under 
the destroying operation of insects. As soon as 
a tree falls, one tribe attacks its bark, and thou- 
sands of holes are bored into the trunk by others. 
The rain thus finds access, and assists the decay. 
