14 OUTLINES OF ENTOMOLOGY. 



chapter. There are nine or ten, sometimes eleven pairs of them, two 

 on the thorax and the others on the abdomen. • 



The only appendages of the abdomen are the organs of reproduc- 

 tion, which, in some species, as the bee and the wasp, are connected 

 with those of defense, in the form of stings. They consist, externally, 

 of various sorts of forceps or claspers in the male, and of saws, augers, 

 swords, and more commonly, piercers and stings in the female. All of 

 these instruments are very ingenious in their construction and admi- 

 rably adopted to the work for which they are designed. They will be 

 described in detail when the species to which they pertain are under 

 consideration. 



CHAPTER V. 



INTERNAL STRUCTURE OF INSECTS. 



The internal structure of insects consists of the Muscular, Nervous 

 and Circulatory systems, together with the organs of Respiration, Nutri- 

 tion and Secretion. 



The examination of these parts is a work of great difficulty, owing 

 to their extreme delicacy and minuteness. Much of it requires a high 

 power of microscope and the skill of a hand experienced in dissecting ; 

 consequently the descriptions — as with the characters of external struc- 

 ture — cannot be easily verified by the observations of the tyro. Only 

 a brief account, therefore, will be attempted in this chapter. 



The Muscular system lies just within the external crust, or body- 

 wall, to which it is closely attached. Its use is to hold the segments 

 and their various appendages in place, and to move them according to 

 the pleasure or necessity of the insect. It consists of a great number 

 of distinct fibers, not gathered into bundles like those of higher animals, 

 but spread out in thin layers over the parts requiring their action. In 

 their arrangement the muscles correspond to the jointed structure of 

 the body. Each segment has muscles that stretch from its front edge 

 to the front edge of the one succeeding it, and others that in like man- 

 ner connect the hinder edges. There are also bands of muscular fibers 

 passing around the body and others still that extend obliquely from one 

 joint to another. The muscles of insects are a pale yellow color and 

 of a soft, jelly-like consistence. But, although so delicate in texture, 

 their contractile power is surprising. Thus, many insects, of which 

 the flea is a good example, are enabled to leap more than one hundred 



