STRUCTURE OF ADULT INSECTS. THE IMAGO. 35 



CHAPTER V. 



STRUCTURE OF ADULT INSECTS. — THE IMAGO. 



We have thus far traced the appearance and progress 

 of the immature insect through its various stages of 

 Egg, Larva and Pupa ; but it is in the Adult Insect or 

 Ima(/o, to which we are now to turn our attention, that 

 we find some of the most compact and beautiful mechan- 

 ical structures of the entire animal kingdom. The ear- 

 lier stages were each preparatory for this adult condi- 

 tion, and thus we find in the Imago the most definite as 

 well as beautiful arrangement of parts. 



For convenience, we will adopt the plan of consider- 

 ing first, the JEjxternal A7iatomy y and second, the In- 

 ternal Atiatomy of the Imago. 



EXTERNAL STRUCTURE OF THE IMAGO. 



The External Anatomy refers to the arrangement of 

 the apparent parts of the body in relation to each other, 

 and may be more readily used in the ordinary observa- 

 tion and classification of Insects; while the Internal 

 Anatomy treats of the muscles, nerves, arteries, veins, 

 spiracles, digestive organs, &c., and often requires much 

 labor and microscopes of high power for its investiga- 

 tion. 



In the external anatomy of the adult insect there are 

 two general points of structure that may be considered 

 as primary. 



