350 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 Bombyx mori, and in some of the Psychidae. The eggs 
Fic, 199.—Larva of Bombyx 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, 
Fic, 200.—Head, pro-leg, and leg of Bombyx mort, 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 
