35° 



ZOOLOGY 



ganglia of the caterpillar abort, and the next four or five per- 

 sist. There are eight stigmata, the anterior between the pro- 

 and meso-thorax, the remaining seven in the abdomen ; the 

 tracheae which arise from the latter bear air vesicles. 



The length of the proboscis varies, and is said to correspond 

 with the position of the nectaries in the various flowers upon 

 which the Lepidoptera feed. The nectar is sucked up the 

 hollow tube formed by the maxillae by the action of a suctorial 

 stomach which communicates by a short stalk with the oesoph- 

 agus. There are as a rule six Malpighian tubules. 



The sexes are usually distinct, the male being in many 

 cases the more beautiful. A few Lepidoptera are partheno- 

 genetic. This phenomenon occurs sometimes in the silk-worm 

 moth Bomhyx mori, and in some of the Psyehidae. The eggs 



Fig. 199. — Larva of Bonibyx mori. 



are usually laid on such plants as the larvae, when hatched, feed 

 upon. The larvae are commonly known as caterpillars ; these 

 bear three pairs of five-jointed thoracic feet, and, in addition. 



Pio. 200. — Head, pro-leg, and leg of Bombyx mon, larva. 



two to five pairs of unjointed pro-legs, which may occur on the 

 third to the sixth abdominal segments, and on the last. These 



