METAMORPHOSIS IN LEPIDOPTERA. 7 



dermal origin (see, vol. i., p. 19) throw off their outer covering at each 

 moult as exuviae. Thus the integument, hairs, and setae are accom- 

 panied by the .eye-facets, the lining of the mouth, pharynx, mandibles 

 and the lining of the tracheal tubes, whilst Newport adds that " the 

 lining of the large intestines is detached with the skin of the posterior 

 part of the body," and that " the lining of the portion of the alimen- 

 tary canal which extends from the termination of the oesophagus to the 

 insertion of the so-called biliary vessels, is also detached and becomes 

 completely disintegrated." Packard notes that in the larva of Datana, 

 the tracheae at the time of ecdysis undergo a complete histolysis, and 

 arise de novo from hypodermal cells, the so-called spiral threads 

 originating from elongated peritracheal nuclei. This, he adds, is " also 

 undoubtedly the case with the salivary ducts, which are strengthened 

 and rendered elastic by taenidia like those of the trachea?. As the 

 urinary tubes are diverticula of the proctodeum, itself an ectodermal 

 invagination, they may also, though not lined with a chitinous intima, 

 be renewed. With little doubt the intimae of the ducts of poison, 

 spinning, and most, if not all the other, glands, though certainly the 

 dermal glands, are exuviated." 



Howgate noticed (under the microscope), whilst observing a small 

 immature transparent Geometrid larva, peculiar internal movements, 

 " each segment, commencing at the head, becoming elongated within 

 the outer skin, whilst the next ones remained in their former state. 

 Each segment in its turn behaved in this manner until the last was 

 reached, when the motion was reversed and proceeded towards the head, 

 when it was again reversed. . . . The whole proceeding appeared 

 as if the larva was gliding within itself, segment after segment, the 

 outer skin remaining as if held by the other segments, whilst the parti- 

 cular one in motion freed itself within. After remaining motionless 

 for a short interval, the skin near the head swelled and burst open at 

 the back. . . . Presently the head of the new caterpillar came 

 out, pushing forward the old one. . . . After a short struggle 

 the new true legs appear, pushing off and treading under foot the old 

 ones, then, by a violent wriggling movement, the abdominal legs are 

 extricated. After this all is clear, and the larva, quite exhausted, coils 

 itself up and literally pants for breath " [Naturalist, 1885, p. 366). 



Chapman notes that when the larva of Gharaxes jasius moults, the 

 head of the larva retreats from the effete head to the prothoracic seg- 

 ment, leaving only the mouth parts within the old head. He says that 

 this is easily observed in many species of larvae, but it struck him as 

 being curious in this species because the four horns or spines of the new 

 head were not directed backwards but laterally, two to either side, 

 under the skin of the prothoracic segment. The same observer writes 

 (Ent. Record, ix., pp. 217-218) : " In many Noctuid (and other) larvae 

 with transparent heads, it is easily seen at the period of moult, that 

 the old head is not entirely filled by the new head, but that the old 

 head is largely occupied by fluid which bathes the new skin beneath the 

 old one. At this stage, the head has really moulted, being chiefly 

 within the prothorax. This fluid contains some chitinous matter in 

 solution, and the dampness of the newly-changed larva dries up into 

 a superficial layer of chitinous material. . . . At the larval moults 

 of ( '. jasius (as with many other species) the head is cast entire, but at 

 the pupal moult it splits up. At a larval moult the larva eats the 



