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long tube, and serving as a temporary receptacle for food. In herbiv- 

 orous insects the crop contains glucose formed from starch by the 

 action of saliva or by the secretion of the crop itself; in carnivorous 

 insects this secretion converts albuminoids into assimilable peptone- 

 like substances. 



Next comes the enlargement known as the proventriculus, or 



gizzard, which is present in many 

 insects, especially Orthoptera and 

 Coleoptera (Fig. 148), and is 

 usually found in such mandibulate 

 insects as feed upon hard sub- 

 stances. The proventriculus is 



-d 



FIG. 148. 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, oesophagus; p, proventricu- 

 lus; r, reservoir. After KOLBE. 



PIG. 149. Digestive system of Myrme- 

 leon larva, c, caecum; cr, crop; in, mid 

 intestine; mt, Malpighian tubes; s, spin- 

 neret. After MEINERT. 



lined with chitinous teeth or ridges for straining the food, and has power- 

 ful circular muscles to squeeze the food back into the stomach, as well as 

 longitudinal muscles for relaxing, or opening, the gizzard. The pro- 

 ventriculus not only serves as a strainer, but also helps to comminute 

 the food, like the gizzard of a bird. 



