IXSECTA. 81 



tern, and makes the greater part of the body appear like 

 a lung. These tubes communicate externally by open- 

 ings placed on each side of the body, and are termed 

 stigmata. This arrangement of the organs for aerial 

 respiration is plainly discernible in the structure of the 

 naked caterpillar, -where the filamentous canals are quite 

 visible to the naked eye, and may be counted. If the 

 body of the insect is covered with oil or varnish, it is at 

 once suffocated ; life is even more suddenly extinct than in 

 the severance of the' head from the trunk of a human 

 being. The organs of nutrition are variously fashioned, 

 differing according to the nature of the food required by 

 the different races. Some possess strong antennae or 

 feelers ; others have their mouths armed with a sort of 

 lancet-like beak or piercer ; and another class are pro- 

 vided with a tubular trunk or sucker. The tube com- 

 mences at the mouth and extends along the whole length 

 of the body, as in the higher races of animals. The 

 work is performed very rapidly, therefore many of them 

 are exceedingly voracious. The body is divided into 

 three parts, namely, head, thorax, and abdomen, which 

 are separated into three distinct segments, but bound 

 together by a strong articulation or joint ; in the Crus- 

 tacea, * however, the head and thorax frequently form but 

 one piece. The genuine insect passes through gradual 

 stages of development before it attains the perfect form 

 it is destined to assume ; these are, first, larva, then 

 caterpillar, nympha or chrysalis, and, lastly, a perfect 

 insect ; nevertheless, the Crustacea form an exception to 

 this manner of change, although they are subject to a 



* This great branch of the animal kingdom is composed of five dis- 

 tinct classes of animals; namely, insects, myriapods, arachnidans, 

 crustaceans, and annelidans, all distinguishable from each other. TV. 



4* 



