CLASS HEXAPODA. 



The body of the normal insect, then, is made up of sev- 

 enteen rings or segments. 



The blood is purified by having air distributed over 

 the entire body by means of small tubes, the trachece 

 (tra'ke e), the external openings of which are called spir- 

 acles (spir'a klz). 



The digestive apparatus (ap pa ra'tus) is more com- 

 plicated than in Crustacea, as 

 will be seen by reference to 

 the figure. 



The most striking peculiar- 

 ity, however, is the character- 

 istic series of changes, meta- 

 morphoses, which many forms 

 pass through before they reach 

 the adult condition.* 



Most INSECTS are oviparous 

 (o vip'a rtts). The young, burst- 

 ing from the egg, is called the 

 larva (lar'va). It may be an 

 adult in miniature, or it may 

 resemble the adult in several 

 particulars, as does the young of 



Digestive Apparatus of Insects, a, Head. 



the Grasshopper (g pas' hop per) ; 6, Antenna, c, Jaws, d, Palpi, e, 



,., (Esophagus. /, Crop, gr, Gizzard, h, 



it may be WOrm-llke, as the Stomach, i, Intestine, j. Rectum. 



young of flies, maggots, (by no 



means true worms) ; may be provided with walking ap- 

 pendages, as the young of butterflies, and moths, rater- 

 pillars : or may be grub-like, as the young of beetles. 

 In the first case, development is direct, i. e., without 

 metamorphoses ; in the second, through a series of 

 moults, the pupa (pu' pa) stage is reached ; while a final 



* Compare with metamorphoses of Crustacea. 



