THE CATERPILLAR AND THE MOTH 



the press and into the spinneret is seen from the side 

 at D. 



The silk liquid is gummy and adheres tightly to what- 

 ever it touches, while at the same time it hardens rapidly 

 and becomes a tough, inelastic thread as it is drawn out 

 of the spinneret when the caterpillar swings its head away 

 from the point of attachment. 



The mouth of the caterpillar lies between the jaws and 

 the lips. It opens into a short gullet, or oesophagus, which, 

 with the pharynx, constitutes the first part of the alimen- 

 tary canal (Fig. 154, P/iy, Oe). The rest of the canal is a 

 wide tube occupying most of the space within the cater- 

 pillar's body and is divided into the crop {Cr), the stomach, 

 or ventriculus {Vent), and the intestine [hit). The crop is 

 a sac for receiving the food and varies in size according 

 to the amount of food it contains (Fig. 156 A, B, Cr). 

 The stomach {Vent) is the largest part of the canal. Its 

 walls are loose and wrinkled when it is empty, or smooth 

 and tense when it is full. The in- 

 testine {Int) consists of three divi- 

 sions, a short part just back of the 

 stomach, a larger middle part, and a 

 saclike end part called the rectum 

 {Reef). Six long tubes {Mai) are 

 wrapped in many coils about the in- 

 testine and run forward and back in 

 long loops over the rear half of the 

 stomach. The three on each side Fig. 157. Crystals 

 unite into a short basal tube, which fZief'of^he'^em 

 opens into the first part of the intes- caterpillar, which are 



/-fi 1 1- 1 1 ejected into the walls 



tine. 1 he terminal parts of the tubes of the cocoon 



are coiled inside the muscular coat 



of the rectum. These tubes are the Malpighian tubules. 



When a tent caterpillar goes out to feed, the fore part 

 of its body is soft and flabby; when it returns to the tent 

 the same part is tight and firm. This is because the tent 

 caterpillar carries its dinner home in its crop, digests it 



[289] 



