PROCESS OF MOULTING 611 



worm is about to moult. Every 10 days the same operation is repeated. From 

 the fourth moulting to the time of beginning the cocoon the period is about 

 10 days. (Amer. Naturalist, i, pp. 37, 38.) 



Little has been recorded as to the exact mode of casting the larval skin in 

 Coleoptera. Slingerland states that Euphoria inda when pupating sheds the 

 larval skin off the anal end in the same way as in caterpillars, while in Pelidnota 

 punctata the larval skin splits down the whole length of the back, retains the 

 larval shape, and forms a covering for the pupa which remains inside. (Can. 

 Entomologist, xxix, p. 52.) The old larval skin in the Coccinellidee and certain 

 Chrysomelidae is retained crumpled up at the end of the body, while in Dermes- 

 tes, Anthrenus, etc., it cloaks the pupa. 



Not only is the integument, with its hairs, setae, and other armatures, as well 

 as the cornea or facets of the eyes, shed, but also all the lining or intima of 

 those internal organs which have been originally derived by an ingrowth or 

 invagination of the ectoderm are likewise cast off, with the probable exception, 

 of course, of the mid-intestine, which is endodermal in its origin. Even so early 

 an observer as Swammerdam noticed that the internal lining of the alimentary 

 canal comes away with the skin. He states that the larva of Oryctes nasicornis 

 sheds both the lining of the colon, and of the smaller as well as the larger 

 branches of the tracheae. 



Careful observations are still needed on the internal changes at ecdysis of 

 most insects. Newport seems to have observed more closely than any one else, 

 notwithstanding the great number who have reared caterpillars but have not 

 carefully observed these points, the extent of the process internally. He informs 

 us: "The lining of the mouth and pharynx, with that of the mandibles, is 

 detached with the covering of the head, and that of the large intestines with 

 the skin of the posterior part of the body, and besides these also the lining of the 

 tracheal tubes. The lining of the stomach itself, or the portion of the alimentary 

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

 the so-called biliary vessels, is also detached, and becomes completely disinte- 

 grated, and appears to constitute part of the meconium voided by the insect on 

 assuming its imago state." (Art. Insecta, p. 876.) Newport states on another 

 occasion that he had "noticed the remai-kable circumstance [now explained 

 by the fact that the mid-intestine is of endodermal origin] that the mucous 

 lining of the true ventriculus was not cast off with the rest, but was discharged 

 with the fecula." J Burmeister also observed that the smaller tracheae as well 

 as the internal tunic of the colon of Libellulse are shed. 



In the apodous larvae of Hymenoptera which live in cells, as we have observed 

 in those of Bombus, during the process of moulting, the delicate skin breaks 

 away in shreds, probably owing to the tension due to the unequal growth of the 

 different parts of the body. " Thus after the skin beneath has fully formed, 

 shreds of the former skin remain about the mouth-parts, the spiracles, and anus. 

 Upon pulling upon these, the lining of the alimentary tube and tracheae can be 

 drawn out, sometimes, in the former case, to the length of several lines." 2 We 

 then added, " As all these internal systems of vessels are destined to change 

 their form in the pupa, it may be laid down as a rule in the moulting of insects 

 and Crustacea, that the lining of the internal organs, which is simply a continua- 

 tion of the outer tegument, or arthroderm, is, in the process of moulting, 

 sloughed off with that outer integument." We have satisfied ourself that in 

 the larvae of the Lepidoptera (e.g. Datana) the tracheae at the time of ecdysis 



J Trans. Ent. Soc. London, iii, p. xv. See also Ashton, R. J., Trans. Ent. Soc. 

 London, iii, 18H-1.'!, pp. 157-159. 



2 Proc. Bust. Soc. Nat. Hist., x, 18<>6, p. 283. 



