44 THE INSECT WORLD. 
“Tt leaves,” says Réaumur, “a portion of the thorax of the 
enat, easily to be recognised by the freshness of its colour, which 
is green, and different from the skin in which it was before 
enveloped, uncovered. 
“As soon as the slit is enlarged,—and to do so sufficiently is 
the work of a moment,—the fore part of the perfect insect is not 
long in showing itself; and soon afterwards the head appears, 
rising above the edges of the opening. But this moment, and 
those which follow, until the gnat has entirely left its covering, 
are most critical, and when it is exposed to fearful danger. This 
insect, which lately lived in the water, is suddenly in a position 
in which it has nothing to fear so much as water. If it were 
upset on the water, and the water were to touch its thorax or body, 
it would be fatal. This is the way in which it acts in this critical 
position. As soon as it has got out its head and thorax it lifts 
them as high as it is able above the opening through which they 
had emerged, and then draws the posterior part of its body 
through the same opening; or rather that part pushes itself 
forward by contracting a little and then lengthening again, the 
roughness of the covering from which it desires to extricate itself 
serving as an assistance. 
“A larger portion of the gnat is thus uncovered, and at the 
same time the head is advanced farther towards the anterior end 
of the covering ; but as it advances in this direction, it rises more 
and more, the anterior and posterior ends of the sheath thus 
becoming quite empty. The sheath then becomes a sort of boat, 
into which the water does not enter; and it would be fatal 
if it did. The water could not find a passage to the farther 
end, and the edges of the anterior end could not be submerged 
until the other was considerably sunk. The gnat itself is the 
mast of its little boat. Large boats, which pass under bridges, 
have masts which can be lowered; as soon as the boat has passed 
the bridge the mast is hoisted up by degrees, until it is perpen- 
dicular. The gnat rises thus until it becomes the mast of its own 
little boat, and a vertical mast also. It is difficult to imagine how 
it is able to put itself in such a singular, though for it necessary, 
position, and also how it can keep it. The fore part of the boat is 
much more loaded than the other, but it is also much broader. 
