ANATOMY AND PHYSIOLOGY 



117 



FIG. 146. 



Mid intestine (mesenteron) : ventriculus (stomach). 



Hind intestine (proctodaum) : pyloric valve, ileum, colon, 

 rectum, anus. 



Stomodaeum. The mouth, the anterior opening of the 

 food canal, is to be dis- 

 tinguished from the 

 pharynx, a dilatation for 

 reception of food. In 

 the pharynx of manclib- 

 ulate insects the food is 

 acted upon by the saliva ; 

 in suctorial forms the 

 pharynx acts as a pump- 

 ing organ, in the manner 

 already described. 



The ccsophagus is com- 

 monly a simple tube of 

 small and uniform cali- 

 ber, varying greatly in 

 length according to the 

 kind of insect. Passing 

 between the commissures 

 that connect the brain 

 with the subcesophageal 

 ganglion (Fig. 113), the 

 oesophagus leads grad- 

 ually or else abruptly 

 into the crop or gizzard, 

 or when these are absent, 

 directly into the stomach. 

 In addition to its func- 

 tion of conducting food, 

 the oesophagus is some- 

 times glandular, as in the grasshopper, in which it is said 

 to secrete the "molasses "which these insects emit. 



Digestive system of a beetle, Carabus. a, 

 anal gland; c (of fore gut), crop; c (of 

 hind gut), colon, merging into rectum; d, 

 evacuating duct of anal gland; g, gastric 

 caeca ; i, ileum ; m, mid intestine ; mt, Mal- 

 pighian tubes; o, ccsophagus; p, proventricu- 

 lus; r, reservoir. After KOLBE. 





