[Illustration: Fig. 211.--Lozenge-shaped net.]
During the third age the number of the meals is kept to four, the first being given towards five o'clock in the morning, and the last between ten and eleven o'clock at night. The leaf is cut into much larger pieces, and distributed as equally as possible. The _délitement_ and the _dédoublement_ are proceeded with as in the preceding age. One begins to find pretty often during this period of the life of worms, some _luisettes_--that is to say, worms which have not strength enough to moult. They are larger than those just woke up, and that have not as yet eaten, and are shiny. They must be carefully removed, for they will not be long before they die, and infect the air of the room.
During the fourth age they no longer cut the leaves, but give them a great deal more at once. The result is that the litters increase in thickness, and that the _délitement_ must be performed oftener; for the rest, four meals are always necessary. Many _luisettes_ may be seen during the fourth age. The moult which follows the fourth age is the most critical phase in the life of the silkworm. During their sleep they are a prey to acute suffering, and are plunged into a state of lethargy which resembles death. The dryest and cleanest litters diffuse very soon a sickly smell. This moult lasts from thirty-six to forty-eight hours. During this time the room should be kept to at least 22° Centigrade.
When they awake out of this last sleep the attendant should continually be on his guard, as it is then that diseases break out. The worms suffering from these different diseases have received different names. There are besides the _luisettes_ the _arpians_--that is to say, worms that have exhausted all their energy in the work of the last moult, and have not even strength to eat--the _yellow_, or _fat_ worms, which are swollen, of a yellowish colour, and which very easily die; the _flats_ or _mous_, the soft or indolent ones which, after having eaten a great deal and become very fat, die miserably, and enter into a state of putrefaction. And lastly, it is at this age that the _muscardine_, which hardly shows itself at any other age of the insect, appears with great intensity.