THE PERFECT INSECT. 
body, and with its tail, all of which it employs for rowing, balanc 
ing, and guiding itself in the water, the tail playing the part of 
the rudder. 
41. Such is the mobility of these members, that even when the 
creature is in repose, all the paddles are in rapid motion; the 
steering prong of the tail alone being at rest. 
Independent of its faculty of locomotion by means of its legs, 
paddles, and tail, it possesses a power of leaping and springing in 
the water,, by bending its body backwards, and then suddenly 
straightening it; by this movement it raises itself to the surface 
with great celerity. 
42. During the second stage of the life of this insect, called the 
state of chrysalis, it retains the faculty of swimming; its motions 
are altogether subservient to its will, and it leaps with great ala¬ 
crity. As the epoch, however, approaches at which it is to pass 
into the third and most perfect state, in which it receives the name 
of day-fly, some parts of it assume a metallic lustre, just as if 
the thin casing in which it is wrapped like a mummy, were partly 
filled with mercury; this casing is so thin and translucent, that 
every part of the body of the perfect insect, which is soon about 
to emerge from it, is plainly enough visible through it. The me¬ 
tallic appearance, just mentioned, is supposed to arise from the 
evolution of a small quantity of gas from the body of the insect 
in the change which it is undergoing; this gas, by insinuating 
itself between the case of the chrysalis and the body of the insect, 
helps to detach the former from the latter, and thus facilitates 
the natural process by which the insect emerges from its prison. 
The envelope of the chrysalis is adapted to the form and members 
of the insect, just as a glove is to the hand, so that after the insect 
has escaped from it, this envelope will exhibit with great precision 
its shape and proportion?. 
43. When the creature has divested itself of its envelope, it 
remains apparently inert' for a few minutes on some neighbouring 
Fig. 31. 
\ 
plant, where it carefully cleanses its wings, and divests them of 
the last pellicle of the sheath in which they had been inserted ; 
it then assumes the beautiful form, and exercises the functions 
79 
