THE CATERPILLAR AND THE MOTH 



upper wall of the structure is ordinarily collapsed into 

 the cavity of the bulb, but it is capable of being lifted by 

 strong muscles inserted upon it from the walls of the 

 head. The alternate opening and closing of the bulb 

 sucks the liquid food up through the tube of the pro- 

 boscis and forces it back into the gullet. The moths and 

 butterflies are thus sucking insects, as are the aphids and 

 cicadas, but they are not provided with piercing organs, 

 though some species have a rasp at the end of the pro- 

 boscis which is said to enable them to obtain juices from 

 soft-skinned fruits. 



With the tent caterpillar, it is interesting to note, the 

 maxillae are much longer in the pupa (Fig. 159 I, Mx) 

 than they are in either the caterpillar or the adult moth 

 (Fig. 162, A/.v), as if nature had intended the tent cater- 

 pillar moth to have a proboscis like that of other moths, 

 but had then changed her mind. The real meaning of 

 this is that the moths of the present-day tent cater- 

 pillars are descended from ancestors that had a functional 

 proboscis in the adult stage like that of other moths, and 

 that the reduction of the proboscis of the modern moths 

 has taken place in times so recent that the organ has not 

 yet been suppressed to the same degree in the pupa. 



The alimentary tract of the tent caterpillar moth is 

 very different from that of the caterpillar. In the cater- 

 pillar, the organ consists of three principal parts (Fig. 

 164 A), the first comprising the oesophagus (Of) and the 

 crop (Cr), the second being the stomach, or ventriculus 

 {Vent), and the third the intestine (hit). In an adult moth 

 that is almost mature, but which is still inside the pupal 

 shell (B), the oesophagus has become a long narrow tube 

 (Oe) at the rear end of which the crop forms a small sac 

 {Cr) projecting upward, which may contain a bubble of 

 gas. The stomach has contracted to a pear-shaped bag 

 with very thin transparent walls, and is usually filled 

 with a dark-brown liquid. The intestine has changed 

 radically in form, for it now consists of a long, slender, 



[309] 



