34 MECHANICAL FUNCTIONS. 



the size of the preceding claw, or its mate, and this is the 

 reason why we often see both lobsters and crabs with one 

 of these parts much smaller than the other. 



INSECTS. 



82. This division of animals derives its name from the 

 Latin insecto, which signifies " to cut " because most of 

 them appear nearly divided by an incision through the 

 middle. 



83. The natural history of this class of animals affords 

 a highly interesting, useful, and curious field of inquiry. 

 It is a subject, in which it appears to us, the most incuri- 

 ous can hardly avoid to take more or less interest, since its 

 objects are so common and so diversified in appearance, as 

 to have forced themselves, more or less, on the notice of 

 every one who has his perfect senses. 



84. Insects have organs of locomotion, sensation, sight, 

 and taste, and many of them are endowed with the most 

 wonderful instincts ; but they have neither heart, arteries, 

 nor lungs, though some of them have parts analogous to 

 the two latter organs. 



85. Changes in the forms of Insects. Most insects be- 

 gin their lives in the form of larva?, or worms, the power 

 of flight being reserved until after having passed through 

 several preparatory changes, they attain their perfect state. 

 These changes are termed metamorphoses, and are most 

 conveniently seen in the lepidopterous, or butterfly 

 tribes. 



86. Beginning with the hatching of the egg, laid by 

 the butterfly, the following changes take place, before a 

 butterfly is again produced. Most of these eggs are no 

 larger than mustard-seeds, and are attached to the leaves 

 of plants on which the future larva, or caterpillar, is to 

 feed. In this the butterfly is directed by that most 

 mysterious property called instinct, and by which she 

 never fails to place her eggs on such plants as are the 

 most proper food for her future progeny. Thus somt 



What is said of the lobster acquiring a new claw in place of one de 

 stroyed? Whence is the term insect derived? What organs have insects . 

 In what form do insects begin their lives ? 



