INSECTA. 123 



The organs of locomotion consist of a coxa of two pieces, a 

 femur, an unarticulated tibia and a tarsus. The number of 

 phalanges vary from three to five,, and the last joint is usually 

 terminated by two hooks. 



The abdomen presents nine or ten segments, some of which 

 are however frequently reduced. 



Explanation of Fig. A, PL 34, Aptera: 1, the head; 2, 

 the maxillary palpi ; 3, three segments of the thorax ; 4, an- 

 terior wing of the mesothorax ; 5, posterior wing of the me- 

 sothorax; 6, the thigh (femur); 7, tibia; 8, tarsus. 



Fig. A, PL 35. Coleoptera: 1, the head; 2, the protho- 

 rax ; 3, the corselet ; 4, the mesothorax ; 5, the rnetathorax ; 

 6, the elytra ; 7, the wings ; 8, the two first rings of the ab- 

 domen. 



There are some Insects which pass through their stages of 

 life under three different forms; viz., that of larvce, of pupa, 

 and of perfect Insects ; these changes are termed the meta- 

 morphosis. The Butterfly is an example : the eggs of the 

 Butterfly are hatched and produce animals, called Caterpil- 

 lars, with an elongated body, divided into rings, having a 

 head with jaws and several small eyes ; feet six, scaly and 

 anterior, the rest membranous and posterior. In this state 

 these animals live for some time, frequently changing their 

 skin ; finally from the skin of the Caterpillar issues a totally 

 different being, of an oblong form and without distinct limbs, 

 it soon ceases to move, and remains a long time apparently 

 dead, and is called a Chrysalis. In time the skin of the 

 Chrysalis splits, and therefrom issues the Butterfly, moist and 

 with short flabby wings ; it soon however dries, the wings 

 enlarge, and the animal is perfect and ready for flight. 



All Insects do not pass through these stages. Those with- 

 out wings do not change, and are said to be without meta- 

 morphosis. Of those which have wings many only experi- 

 rience the change of receiving them ; these are said to undergo 

 a semi-metamorphosis. The remainder are said to experience 

 a complete metamorphosis. 



