12 ENTOMOLOGY. 



projections lining it. The apparatus of teeth does not 

 triturate the food, which has been sufficiently comminuted 

 by the jaws. This is proved by the fact, says Plateau, that 

 the parcels of food are of the same form and size as those 

 in the crop, before passing through the proventriculus. 

 The six large lateral pouches (caeca) emptying into the 

 commencement of the stomach (ventriculus) are true glands, 



FIG. 6. Digestive canal of a Carabid beetle. 6, oesophagus; c, crop; d, proven- 

 triculus; /, chyle-stomach; g, posterior division of the stomach: /, the two 

 pairs of urinary tubes; h, intestine; fc, rectum; I, anal glands. After Dufour, 

 from Judeich and Nitsche. 



which secrete an alkaline fluid, probably aiding in digestion. 

 In the stomach (ventriculus) the portion of the food which 

 has resisted the action of the crop is submitted to the action 

 of a neutral or alkaline liquid, never acid, secreted by special 

 local glands or by the lining epithelium. In the ileum and 

 colon active absorption of the liquid portion of the food 

 takes place, and the intestine proper (ileum and colon) is 

 thus the seat of the secondary digestive phenomena. The 

 reaction of the secretion is neutral or alkaline. The rectum 

 is the stercoral reservoir. It may be empty or full of liquids, 

 but never contains any gas. The liquid products secreted 

 by the urinary tubes are here accumulated, and in certain 

 circumstances here deposit the calculi or crystals of oxalic, 

 uric, or phosphatic acid. Insects, says Plateau, have no 

 special vessel to carry off the chyle, such as the lacteals or 

 lymphatics of vertebrates; the products of digestion viz., 

 salts in solution, peptones, sugar in solution, and emulsion- 

 ized greasy matters pass through the fine coatings of the 



