LE96ON 40.] 



NUTRITION IN INSECTS. 



143 



FIG. 236. 



species possessing it), the gummy fluid becoming instantly inspissated 

 when brought into contact with the atmosphere (Fig. 236), and forms 

 a thread ; during all this time the poor crea- 

 ture's body is sadly contorted, and it gives 

 unmistakable evidence of great sickness, 

 pain, and suffering. That the change the 

 animal is about to undergo is really attend- 

 ed with such severe distress, is apparent 

 from the fact that many of them die during 

 the process. 



642. The alimentary canal (235) com- 

 mences by a wide funnel-shaped cavity, the 



pharynx (e) ; to this succeeds the oesophagus 8 P inneret ' Cossu8 Mgniperda. 

 (f), which dilates into a membranous crop, filled with deep longitudinal 

 folds, by which means its internal capacity can be greatly increased 

 (g). After the food has lain macerating here for a while, it is trans- 

 ferred to the long stomach (h), provided with a powerful muscular 

 coat externally, and lined with a mucous membrane. Here the food 

 is reduced to chyme, and allowed to pass through the pyloric valve 

 (i) into the ileum (&), where it meets with the biliary secretion 

 passed through the connecting gall ducts (Z, Z), and the chyme is 

 transformed to chyle. 



The Ileum terminates in a short, straight colon, which, as com- 

 monly happens, enlarges slightly, prior to its termination. 



643. The liver exhibits a series of pro- 

 tuberances, which are alternate. A highly 

 magnified view is given (Fig. 237), in which 

 it will be seen that they are cells, each being 

 filled with (apparently) globules, of an oily 

 fluid. 



The cut ends of this portion of the liver 

 of a Caterpillar, have discharged an oil, 

 which, in the preserving fluid, has assumed 

 a globular form of variable dimensions, all 

 of them being very much larger than when 

 confined within the cells. This sacculated 

 form of the liver is common to most insects, and may be regarded as 

 characteristic ; moreover, it is always minute and uniform, and can- 

 not be confounded with the lobules of the salivary glands. 



FIG. 237. 



Liver of Caterpillar, 

 magnified. 



