When the moult is approaching, the young ones are made to climb on to boughs having tender leaves, so that they can be moved to litters as thin and clean as possible, and there sleep in a good state of health. When the mass of worms is well awake again, the next thing to do is to take them off the litter on which they moulted, and to give them food. If this problem were proposed to a person strange to the operation which is now occupying our attention--to separate the worms from the faded and withered food upon which they are reposing, without touching them--he would certainly be very much at a loss what to answer. The solution of this problem presented for a long time great difficulties, and occasioned numerous reverses in the rearing. Now-a-days, thanks to the employment of a net, the _délitement_, or taking them off their bed, has become an easy operation.
Over the worms, placed on a table, is spread a net, the meshes of which are broad enough to allow them to pass through. On this net are spread the leaves which are to compose a meal. The worms immediately leave the old food, and get on to the new leaves. They then lift the litter with the worms, and throw away the old leaves, now unoccupied, clean the table, and replace the net with the worms. At the next _délitement_ the first net is found under the litter. Figs. 211 and 212 represent two forms of these nets made of thread.
Thread nets, which were of great use, have been supplanted lately, with great advantage, by paper ones, which were invented by M. Eugène Robert. These are leaves of paper, of a peculiar manufacture, pierced with holes proportioned to the size of the worms which are to pass through them. The paper net can be used advantageously also for separating the worms that are too near together, or, as they say, for the _dédoublement_. Formerly, the _délitement_ and the _dédoublement_ were done by hand--a tedious work, and one that presented serious disadvantages. Now-a-days, as we have seen, the worms themselves perform these two perilous operations.
At the second age they still cut the leaves for the worms, but into larger pieces, and proportioned to their size. During the day the temperature of the room ought to be kept to 21° Centigrade, but it may be lowered by 1° or 2° during the night. Towards the end of this age they have only four meals. When the worms are on the point of going to sleep, their meals are decreased.