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 oesophaXus, which, with the pharynx, constitutes the first part of the alimen- tary canal (Fig. 154 ' Pli.v, Oe). The rest of the canal is a wic{e tube occup.ving most of the space within the cater- pillar's body and is divided into the trop (Cr), the stomach, or ventricul'us (l'ent), and the ilttestMe (l??t). The crop is a sac for receiving the food and varies in size according to the amount of food it contains (Fig. ?56 A, B, Cri. The stomach (Peu) is the largest part of the canal. I ts 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 (Rect). Six long tubes (Mal) are wrapped in many colis about the in- testine and run iorward and back in long loops over the rear hall of the stomach. The three on each side unite into a short basal tube, which opens into the first part of the intes- tine. The terminal partsofthe tubes are coiled inside the muscular coat
Fro. ? 57- Crystals from the Malpighian tubules of the tent caterpillar, which are ejected into the walls of the cocoon
of the rectum. These tubes are the Malpighian tubules. When a tent caterpillar goes out to feed, the fore part of its body is sort and flabbv; 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
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INSECTS
slowly
