Key Technical Points for Silkworm Rearing, Cocoon Harvesting and Cocoon Selling

I) Cocoon harvesting

1. Proper time for cocoon harvesting: After the mature silkworm finishes spinning its cocoon, it molts and pupates. As the pupa develops, the body skin hardens and darkens in color. When the skin color turns yellow, it is the proper time for cocoon harvesting. In the spring silkworm season, it is 6-7 days after mounting on the cocooning frame. In the summer-autumn silkworm season, it is 5-6 days after mounting, and in the late-autumn silkworm season, it is 7-8 days after mounting; generally the cocoons can then be harvested. If cocoons are harvested too early, the silkworm has not yet pupated, and "hairy-foot" cocoons are difficult to dry evenly and suitably during cocoon drying, lowering cocoon quality; moreover, when such cocoons are boiled, the impurities in the silkworm body readily seep out into the cocoon layer, worsening the color of the raw silk. When pupation has just occurred, the tender pupa's body skin easily breaks, and bleeding contaminates the cocoon layer, causing "inner-stained" cocoons; also, during cocoon drying, fat readily seeps out and contaminates the cocoon layer, forming oily cocoons and lowering silk quality. If cocoons are harvested too late, and if the silkworm larva is parasitized by @#@261@#@, the number of maggot-pierced cocoons will increase; in addition, there is the possibility of the silkworm pupa turning into a moth, increasing moth-emergence cocoons.

2. Cocoon harvesting method: When harvesting cocoons, first pick out dead silkworms and rotten cocoons from the frames, and remove grass debris, silkworm droppings and other foreign matter, so as not to contaminate good cocoons. Harvest according to the order of mounting: those mounted first are harvested first, and those mounted later are harvested later. Harvesting movements should be gentle: pick gently and place gently, and keep each type of cocoon separate. After harvesting, spread the cocoons thinly in trays in good time; they must not be piled too thickly, lest heat build up and affect cocoon quality. After harvesting is finished, promptly clean the mounting room and mounting tools, and do a good job of "four-mountain disinfection" to prevent pathogens from spreading and contaminating the environment.

(II) Cocoon selection and cocoon transport

1. Cocoon selection: When harvesting, the good cocoons, inferior cocoons, secondary cocoons and double cocoons should be harvested and placed separately, but some mixing is unavoidable. Therefore, before selling good cocoons, strict cocoon selection work must be carried out to raise the proportion of good cocoons. The cocoon selection site should be bright.

2. Cocoon transport: When transporting fresh cocoons for sale, air cages or dry rice straw should be inserted in the middle of the baskets or creels used for holding cocoons, packed loosely and transported quickly. Plastic bags must never be used to hold cocoons. Movements during transport should be gentle, reducing vibration as much as possible; during transport, protect against sun exposure and rain.

(III) Cocoon selling

Silkworm cocoons can be divided into two categories, reelable cocoons and inferior cocoons, with the following classification standards:

1. Reelable cocoons: refers to cocoons from which raw silk of lower grade can be reeled; it includes most good cocoons and a small portion of secondary cocoons. Good cocoons have normal cocoon shape, cocoon color, cocoon layer thickness and shrinkage wrinkles, with no defects; those with defects but not reaching the standard for inferior cocoons can be reeled into low-grade silk, with a large reeling loss and poor raw silk quality; for example, multi-layer cocoons, lightly yellow-spotted cocoons, lightly wood-marked cocoons, lightly cottony cocoons, lightly malformed cocoons, water-colored cocoons and the like belong to this type of cocoon.

2. Inferior cocoons: refers to cocoons with serious defects that cannot be reeled or are very difficult to reel, and can be used as silk spinning raw material or to make silk floss. Double cocoons, cut cocoons, yellow-spotted cocoons, wood-marked cocoons, oily cocoons, contaminated cocoons, thin-shelled cocoons, shriveled cocoons, rotten cocoons, soft cottony cocoons, stained-head cocoons and the like all belong to inferior cocoons.