438 MOTIONS OF INSECTS. 



that state I have before noticed (Leptis Vermileo), will, when removed 

 from its habitation, endeavour to recover it by leaping. Indeed this mode 

 of motion seems often to be given to this description of larvee by Pro- 

 vidence, to enable them to return to their natural station, when by any 

 accident they have wandered away from it. 



Many apodous larvae inhabit the water, and therefore must be furnished 

 with means of locomotion proper to that element. To this class belongs 

 the common gnat (Culex pipiens\ which, being one of our greatest tor- 

 ments, compels us to feel some curiosity about its history. Its larva is a 

 very singular creature, furnished with a remarkable anal apparatus for 

 respiration, by which it usually remains suspended at the surface of the 

 water. If disposed to descend, it seems to sink by the weight of its body ; 

 but when it would move upwards again, it effects its purpose by alternate 

 contortions of the upper and lower halves of it, and thus it moves with 

 much celerity. The laminae or swimmers, which terminate its anus 1 , are 

 doubtless of use to it in promoting this purpose. It does not, that I ever 

 observed, move in a lateral direction, but only from the surface downwards, 

 and vice versa. Another dipterous larva (Corethra culiciformis\ which 

 much resembles that of the gnat in form, differs from it in its motions and 

 station of repose ; for, instead of being suspended at the surface with its 

 head downwards, it usually, like fishes, remains in a horizontal position in 

 the middle of the water. When it ascends to the surface, it is always by 

 means of a few strokes of its tail, so that its motion is not equable, sed 

 per saltus. It descends again gradually by its own weight, and regains its 

 equilibrium by a single stroke of the tail. 2 A well-known fly (Stratyomis 

 Chamcekon), in its first state an aquatic animal, often remains suspended, 

 by its radiated anus, at the surface of the water, with its head downwards. 

 But when it is disposed to seek the bottom or to descend, by bending the 

 radii of 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. 3 



I have dwelt longer upon the apodous larvae, or those that are without 

 what may be called proper legs, analogous 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 conspicuous 

 in the ordinary routine of nature. But aberrations from her general laws, 

 and modes, and instruments of action, often of rare occurrence, impress 

 us more forcibly than any thing that falls under our daily observation. 



I come now to pedate larvae, or those that move by means of proper or 

 articulate legs. These legs (generally six in number, and attached to the 

 underside of the three first segments of the body) vary in larvae of the 



1 Reaum. iv. t. 43. f. 3. nn. 2 De Geer, vi. 375. t. xxiii. f. 4, 5. 



5 Swamin. Bibl Nat. Ed. Hill, ii. 44. b. 47. a. 



