Nourishment is, of course, a very important item for the growing worms, and the best form of food for the _Bombyx mori_ is the leaf of the white mulberry, which must be young, fresh and dry, but never withered. For this purpose mulberry tree raising has become an important by-industry in itself. Three varieties are found, classified according to the time of budding—early, medium and late. The leaves, therefore, can be found in the correct condition for the various stages in the growth of the worm. The late budding trees are cultivated in more abundance, as the worms are larger at that time and consume more leaves. The soil in which the trees grow is important, as it has been found that one which is rich in certain minerals provides leaves that keep the worms in better physical condition. A cold winter followed by a warm spring develops the leaves well, and the condition of the leaves is one of the most important factors in the whole process. [Sidenote: _Early Development_] Careful selection of the eggs is another matter of prime importance. When the leaves are almost ready, the eggs are brought out of cold storage and subjected to heat for about a month before they hatch out. When the worm hatches it is about the diameter of a hair and less than three-fourths of an inch long. It gnaws a hole through the end of the egg from which it issues. Nourishment at first is taken by sucking the sap of the leaves, which are at this stage chopped into fine pieces; later the leaves are consumed without the necessity of their being chopped up. [Sidenote: _Spinning the Cocoon_] The development is very rapid, the worms consuming their own weight daily. During this period, as has been stated, they shed their skins four times, and after the fourth molt—about one month after hatching—they have assumed their full size. From then on hunger lessens, restlessness grows, and the lifting of the fore part of the body indicates the desire to climb and spin cocoons. For this purpose brush and twigs are provided in the trays, to which the worms attach themselves and begin the spinning process. The silk thread is expelled in a semi-liquid form from two openings underneath the mouth, hardening as it comes in contact with the air. The first threads issued are coarse and rough, having the necessary strength to serve as supports and guys for the cocoon. Gradually the worm is enclosed in the cocoon after three days of continuous spinning, during one of which it is visible and then slowly disappears, though it can be heard working inside. [Illustration: _Worms Feeding_] The worm wastes away as its silk glands are exhausted, and becomes a chrysalis, from which the moth escapes after fifteen to twenty days. [Illustration: _A Nest of Cocoons_] [Sidenote: _Cocoons for Breeding_]