286 MOTIONS OF INSECTS. 
its tail so as to form a concavity, it includes in them a 
bubble of air, in brilliancy resembling silver or pearl ; 
and then sinks with it by its own weight. When it 
would return to the surface it is by means of this bubble, 
which is, as it were, its air-balloon. If it moves upon 
the surface or horizontally, it bends its body alternately 
to the right and left, contracting itself into the form of 
the letter S; and then extending itself again into a 
straight line, by these alternate movements it makes its 
way slowly in the water?. 
I have dwelt longer upon the apodous larvee, or those 
that are without what may be called proper legs, ana- 
logous to those of perfect insects, because the absence 
of these ordinary instruments of motion is in numbers 
of them supplied in a way so remarkable and so worthy 
to be known; and because in them the wisdom of the 
Creator is so conspicuously, or, I should rather say, so 
strikingly manifested—since it is doubtless equally con- 
spicuous in the ordinary routine of nature. But aber- 
rations from her general laws, and modes, and instru- 
ments of action, often of rare occurrence, impress us 
more forcibly than any thing that falls under our daily 
observation. 
I come now to pedate larvee, or those that move by 
means of proper or articulate legs. These legs (gene- 
rally six in number, and attached to the underside of the 
three first segments of the body) vary in larve of the 
different orders: but they seem in most to have joints an- 
swering to the hip (cora); trochanter ; thigh (femur); 
* Swamm, Bibl. Nat. Ed. Hill, ii. 44. b. 47. a. 
