OF INSECTS. 223 



of all in the class of Insects. We have, in the peculiar mouth 

 apparatus of the fly, the large, extremely versatile head, the com- 

 pact thorax, the single pair of wings, and the concentrated abdo- 

 men, a series of specializations, reductions 

 to uniformity, and, in fine, the very acme 

 of cephalization, such as are to be found 

 in no other order of Insects. 



As an illustration of the internal organ- 

 ization of Insects, I have selected one of 

 the moths, (figs. 131, 132,) known as the 

 hawk-moth, or Sphinx. I have already 

 indicated its division into the three distinct regions, head (hd), 

 thorax (//), and abdomen (b to b 1 }. The head carries a pair of 

 feelers, antennae, (an,) and a tubular proboscis, (jo,) with which it 

 sucks up the fluid nectar of flowers and various other juices. 

 A pair of compound eyes project from the right and left sides 

 of the head, like those of the carrion-beetle (fig. 130, vn). The 

 thorax (th) has two pair of wings attached at the sides, and 

 three pair of legs (/). The abdomen consists of eight incon- 

 spicuous rings (b to b ] ). 



The entrance to the mouth is between the two slender, furrowed 

 pieces which together form the proboscis (p). The gullet (gl) 

 passes from the mouth in a straight line through the thorax, to 

 the abdomen, and there joins the stomach (st). The latter is a 

 broad, puckered sac which tapers behind into a considerably con- 

 voluted intestine (i). Near the junction with the gullet is an 

 oval sac which performs the office of a crop (cr). The intestine 

 (i) terminates by an opening (a) at the extreme posterior end 

 of the abdomen. 



The circulatory system possesses such an extreme simplicity 

 as to induce some naturalists to place the Spiders, which seem 



Fig. 132. An ideal end-view of fig. 131. 6, the periphery of the bodv ; /, 

 the base of the legs ; st, the intestine ; ^, the heart ; sg, the super-oesopha^eal 

 ganglions, or brain ; 9, the sub-oesophageal ganglions ; c, the nervous collar ; ov, 

 the pair of reproductive organs; </, the oviducts; o, aperture of J; br l , the 

 respiratory tubes, trachece ; br, external aperture, spiracle, of br l . Original. 



