r 



ALIMENTARY SYSTEM I 25 



demarcation can be pointed out between the two, and the crop 

 may be totally absent. 



In some of the sucking Insects there is a lateral diverticulum, 

 having , a stalk of greater or less length, called the sucking- 

 stomach ; it is by no means certain that the function this name 

 implies "is correctly assigned to the organ. 



The gizzard or proventriculus (French, g4sier ; German, 

 Kaumagen) is a small body interposed in some Insects between 

 the true stomach and the crop or oesophagus. It is frequently 

 remarkable for the development of its chitinous lining into 

 strong toothed or ridged processes that look as if they were well 

 adapted for the comminution of food. The function of the 

 proventriculus in some Insects is obscure; its structure is used 

 by systematists in the classification of ants. The extremity of 

 the proventriculus not infrequently projects into the cavity of 

 the stomach. 



The true stomach, or chylific ventricle {Magen or Mitteldarm 

 of the Germans), is present in all the post-embryonic stages of 

 the Insect's life, existing even in the imagines of those who 

 live only for a few hours, and do not use the stomach for any 

 alimentary purpose. It is so variable in shape and capacity that 

 no general description of it can be given. Sometimes it is very 

 elongate, so that it is coiled and like an intestine in shape ; it 

 very frequently bears diverticula or pouches, which are placed on 

 the anterior part, and vary greatly in size, sometimes they are 

 only two in number, while in other cases they are so numerous 

 that a portion of the outside of the stomach looks as if it were 

 covered with villi. A division of the stomach into two parts 

 is in some cases very marked, and the posterior portion may, in 

 certain cases, be mistaken for the intestine ; but the position of 

 the Malpighian tubes serves as a mark for the distinction of the 

 two structures, the tubes being inserted just at the junction of 

 the stomach with the intestine. 



The intestine is very variable in length : the anterior part is 

 the smaller, and is frequently spoken of as the colon ; at the 

 extremity of the body the gut becomes much larger, so as to 

 form a rectum. There is occasionally a diverticulum or " caecum " 

 connected with the rectum, and in some Insects stink -glands. 

 In some Hemiptera there is no small intestine, the Malpighian 

 tubes being inserted at the junction of the stomach with the 



