802 MOTIONS OF INSECTS. 
head of these pupee is provided at first with a particular 
instrument, which enables them to effect this purpose. 
The anterior part of the head is armed with a pair of 
hooks in form resembling the beak of a bird; and with 
_this, previously to their last change, they make an open- 
ing in the grate which, though it once defended, now 
confines them. But at this moment, perhaps, the in- 
sect has a considerable space of water to rise through 
before she can reach the surface. This is all wisely pro- 
vided for; before she leaves the envelope which covers 
her body, she emerges from the water, and fixes herself 
upon some plant or other object, the summit of which 
is not overflowed. But you will here, perhaps, ask— 
How can a pupa in her envelope, with all her limbs set 
fast, do this? This affords another instance of the wise 
provision of the beneficent Father of the universe for the 
welfare of his creatures. The antennze and legs of this 
tribe of insects, when they are pupz, are not included, 
as is the case with most that are quiescent in that state, 
in the general envelope; but each in a separate one, so 
as to allow it free motion. ‘Thus the insect when the 
time is come for its last change can use them (except the 
hind-legs, which being partly covered by the wing-cases 
remain without motion) with ease. It then stretches out 
its antennae, and steering with its legs makes for the sur- 
face. De Geer saw one just escaped from its case run 
and swim with surprising agility over the bottom of a 
saucer, in which he had put some cases of these flies ; 
and at last when he held a piece of stick to it, it got 
upon it, and having emerged from the water, prepared 
to cast its envelope. It is remarkable, that the envelope 
