i8 ROMANCE OF THE INSECT WORLD CHAP. 



of these organs as is mainly the case with the legs 

 may be said to occur during the pupal period of rest. 

 It follows that the great enlargement of the thorax 

 as seen in the perfect insect does not generally take 

 place until the chrysalis life has progressed. 



The wonderful and delicate organ called a wing 

 is, to all appearances, composed of a simple mem- 

 brane.* In reality it is double ; and between 

 the two tissues a multitude of minute air-vessels 

 ramify through every part, accompanied by canals 

 or passages for the circulatory fluids. Imme- 

 diately after the assumption of the perfect state 

 these tracheae become solidified like the rest of the 

 skeleton. They are hollow for the reception of air, 

 and afford strength and lightness to the wings, the 

 motions of which are intimately connected with the 

 function of respiration. The membranes are con- 

 tinuous with and expanded portions of the common 

 tegument * of the sides of the segments of the 

 thorax. Their surfaces may be transparent, or 

 coated with dusty scales of microscopic size. The 

 distribution of the contained tracheae, or neuration,* 

 and the appendages, though of the highest intrinsic 

 interest, are outside the present subject. 



The abdomen,* the third division of the body of 

 an insect, is the seat of the greater part of the 

 digestive organs, the respiratory and circulatory, 

 and the generative systems. 



The head of some larvae,tlike "the" rest^of the divi- 

 sions of the body, is covered with] soft; flexible skin. 

 Usually it is rounded or oval in form and of harder 

 texture than the other segments. Three great pairs 



