472 INSECTA. 



forming themselves more into the nature of tubes, but not ramifying 

 into smaller and smaller ones : I suspect that it is only the air-vessels 

 dilating for flight when they come to the moth-state. 



The digestive canal in the silk-moth is not changed into a future 

 canal for digestion and absorption of the chyle, as in other insects; 

 therefore the change in this part is not to be given as illustrative of 

 such change in other insects. This canal is divided into oesophagus, 

 stomach, and short gut. In the stomach is often a fine yellow mucus : 

 the principal part of the contents of the stomach and gut is squeezed 

 down the gut to the bag at the anus, which is increased in size and is 

 full of this yellowish-brown mucus. Tbe long yellow tubular bodies, 

 like threads, that lie on the stomach and guts, are now detached from 

 these parts, and are larger or more completely formed. They open into 

 the stomach close to the beginning of the gut, and they are filled for 

 some way with the same substance. The parts of generation are 

 becoming more and more complete. 



The new-formed skin, or moth-skin, becomes thicker and thicker, 

 and in about eight or ten days it begins to separate itself from the 

 external or chrysalis skin, which begins first at the tail. While the 

 chrysalis is enclosed, its external surface is wet; therefore we may 

 conclude that the chrysalis-shell does not readily admit of evaporation ; 

 yet they lose in weight ; for, in one which I weighed, I found it had 

 lost 22 grains. To observe their future operations, it is necessary to 

 remove them out of their silk-cell or pod. On the fore-part of the 

 head, between the eyes, the chrysalis is always wet. 



They are about twenty days in the chrysalis state, and then they 

 begin to shed their chrysalis-coat. The skin opens on the fore-part 

 of the head and allows the body of the moth to be free, and then they 

 begin to make their way out ; but as they cannot escape from the chry- 

 salis-coat while in the silk-pod, we find them at the same time throwing 

 a juice out of their stomach, which had been secreted while in the 

 chrysalis state, wetting the silk where they are to pass through, and 

 then working with their feet to scratch and loosen the cement of the 

 silk, and pushing themselves through it, leaving the chrysalis skin 

 behind. For I observed that the silk in some degree sticks together 

 where it touches, which sticky matter is softened by this juice ; and, in 

 unravelling the silk, the same means is employed with water. This 

 woidd make us suppose that the exterior surface of the silk had on it a 

 mucus capable of being softened by water, for the silk itself is not. 

 As soon as the head emerges from the pod, we find the moth throwing 

 out of its mouth some of the clear water before mentioned ; therefore 

 their oesophagus is still existing ; and, just as they leave the cell, they 



