220 THE MECHANICAL FUNCTIONS. 



with among the innumcrahle hosts of beings which rank un- 

 der this widely extended department of the animal creation. 

 In these minute creatures may be discovered all the me- 

 chanical instruments and apparatus required for the execu- 

 tion of those varied motions which we witness in the larger 

 animals, and which, though almost peculiar to the different 

 classes of these animals, are here frequently united in the 

 same individual. Insects swim, dive, creep, walk, run, leap, 

 or fly, with as much facility as fishes, reptiles, quadrupeds, 

 or birds. But besides these, a great number have also move- 

 ments peculiar to themselves, and of v/hich we meet with 

 no example in other parts of the animal kingdom. 



In attempting to delineate a sketch of the movements of 

 insects, and of the m.echanism by which they are performed, 

 I am compelled, by the great extent of the subject, to confine 

 myself to very general views; and must refer such of my 

 readers as are desirous of fuller information on this subject 

 to the works of professed entomologists. 



The mechanical conditions of an insect in its several states 

 of larva, pupa, and imago, are so widely different, that it 

 will be necessary to consider each separately. In many tribes, 

 however, the difference between the larva and the perfect 

 insect is much less considerable than in others. Those be- 

 longing to the orders of Hemiptera and Orthoptera, for ex- 

 ample, come out of the egg with nearly the same form as 

 that which they have in the mature state; excepting that 

 they are without wings: these organs being added in the 

 progress of their growth, and constituting, when acquired, 

 their perfect or imago condition. 

 « 



§ 4. K/lquatic Larvx. 



Many insects, which, when fully developed, are the most 

 perfectly constructed for flying, are, when in the state of 

 larvae, altogether aquatic animals. Some of them are destitute 

 of feet, or other external instruments of motion, swimming 

 only by means of the alternate inflections of the body from 

 side to side, in the same manner as the Nais, and the Leech. 



