CHAPTER IV 



ANATOMY OF INSECTS INTERNAL 



The general arrangement of the internal organs of an insect 

 may be understood by a study of transverse and longitudinal sec- 

 tions, as shown in Figs. 31 and 32. Attached to the inside of 



FIG. 31. Ideal section through an insect 



a, alimentary canal ; 7z, heart ; ;?, nerve cord ; s, stigmata, or spiracles ; t, tracheal tubes ; 

 /, legs; 7f, wings. (From Riverside Natural History) 



the body wall are found layers of longitudinal and vertical mus- 

 cles which control the body movements. Through the center of 

 the body runs a large tube, the alimentary canal, or digestive tract. 



FIG. 32. Ideal longitudinal section of an insect, showing relative position of organs 



a, alimentary canal ; //, heart ; ;, muscle bands ; n, nerve cord ; r, reproductive organs. 



(After Comstock) 



Just beneath the back is a small, transparent tube, the dorsal blood 

 vessel, or heart. Along the median line, close to the ventral wall, 

 is a series of small white knots, or ganglia, connected by a double 



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