ORGANS OF NUTRITION. 



35 



toneal; the middle, or muscular; and the inner, or mucous. The 

 mucous coat is variously modified, being plaited or folded ; or, 



as in the Orthoptera and carnivorous Coleoptera, it is solidified 

 and covered with rows of strong horny teeth, forming a sort of 

 gizzard. The alimentary canal is held in place by retractor 

 muscles, but principally by exceedingly numerous branches of 

 the main tracheae. 



This canal (Fig. 45) is subdivided into the mouth and pha- 

 rynx, the oesophagus, supplementary to which is the crop, or 

 " sucking stomach" of Diptera, Lepidoptera, and Hymenoptera ; 

 \\\Qproventriculus, or gizzard ; theventriculus, or true stomach, 

 and the intestine, which consists of the ilcum, or short intes- 



FIG. 44. Anatomy of Sphinx ligustri. m, i, q, the nervous cord resting on 

 the floor of the body; at c, the ganglia form a brain-like organ, much larger than 

 the ganglia of the thorax (m) and abdomen (q). From the brain is sent off the 

 subossophageal nerve which surrounds the gullet into which the food is conveyed 

 by the maxilla?, or spiral tongue (), which, when at rest, is rolled up between the 

 labial palpi (&). 



From the nervous cord is also thrown off a pair of nerves to each pair of legs 

 (as at n, o, />) and a branch, d, is sent off from above, distribiiting nerves to the 

 muscles of flight. 



The heart, or dorsal vessel (e,f), lies just beneath the median line of the body, 

 and is retained in place by muscular bands (as at /) as well as by small tracheal 

 branches. 



The alimentary canal (7j, j, <?), forms a straight tube in the head and thorax; ft, 

 the crop, or sucking stomach, which opens into the oesophagus; j, the true, chyle- 

 forming stomach, which contracts posteriorly, and then dilates near its anal outlet 

 into a cloaca (indicated at y, but not distinctly, as it is concealed by the numerous 

 urinary vessels). The urinary vessels also indicated at g, form long tubes (which 

 correspond to the kidneys of Vertebrates), opening into the pyloric end of the 

 stomach. The position of the testes (fc) is the same as that of the ovary, and the 

 dotted line I shows the course of the efferent duct (vas deferens) and also of the 

 oviduct of the female. 



The figure represents a longitudinal section of the insect, the legs and ends of 

 the antennse having been removed. From Newport. 



