CLASS-BOOK OF ZOOLOGY. 125 



SECTION XXXII. 



V. ENTOMOLOGY. 



§ 520. Entojnology is the science which treats of Insects. 

 Insects are oviparous, with white cold blood, and provided 

 with at least six horny organs of motion, and two thread- 

 like organs, placed near the eyes, called Antenna, or 

 feelers. 



§ 521. Insects derive their name from the circumstance, 

 that the head, breast, and extremity of the body are sepa- 

 rated one from the other, as if by an incision ; and in many 

 cases only connected by a thread, as in Hornets. 



§ 522. Insects are oviparous ; that is, they lay eggs, 

 from which proceed individuals, similar to worms, called 

 collectively Larva or Caterpillars in butterflies, Grubs 

 in beetles, and Maggots in bees, wasps, and flies. 



§ 523. The voracity of the larvae of some insects is 

 astonishing. It is well known that a caterpillar consumes 

 in twenty-four hours more than three times its weight. 



§ 524. The larva grows with great rapidity. For ex- 

 ample, the maggot of a meat-fly, in twenty-four hours, 

 becomes 155 times heavier than it was at its birth. 



§ 525. As soon as the larva comes out from the egg it 

 finds abundant food, adapted to its nature ; for insects, 

 under the guidance of their instinct, lay their eggs in the 

 situations best adapted for sustaining their future pro- 

 geny, — as on the leaves of plants, on putrified bodies, or 

 meat, and even in the bodies of other animals. 



§ 526. The larva, after its full growth, is converted 

 into a Nympha, (also called chrysalis or cocoon,) and 

 passes this portion of its life in a state of torpor, without 

 eating or moving, as we see in the cocoons of butterflies ; 

 after a shorter or longer time, however, the skin of the 

 nympha bursts, and the perfect insect comes out. 



§ 527. Insects do more injury than good. -Neverthe- 

 less, many of them are serviceable to man. A number of 

 them feed on carrion, and thus purify the air ; blister- 

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