almost resist complete unwinding. Depending on sex and species, the cocoons measure from one to 1.5 inches long and 0.5 to one inch in diameter.
Harvested cocoons are sorted; all thin-shelled and unreelable ones are artificially heated overnight at 86 degrees centrigrade to kill the pupae.
A dried cocoon produces a light throbbing sound when shaken and weighs only half of the 2.5 gram weight of a fresh cocoon.
After drying, the cocoon are soaked in hot water with soap and acetic acid for 10 -12 minutes to soften the natural gum (sericin) holding the filaments together. After this stage, the cocoons are ready for reeling.
The center accomplishes this task with three manually operated, metal reeling machines, and one reeling machine, all of Japanese design.
To reel, the cocoons are first placed in a basin filled with warm water. Behind the basin is the reeling apparatus which is fixed on a table-high platform. The technician takes the loose end of a filament, threads this through the “eye” of the reeling machine, carries the filament up over two small wheels, and fastens it to a reel. When the reel is turned, the filament is drawn up and wound in one lightly twisted strand. The cocoon bobs up and down in the water as it is unwound.
“Then we remove the strands from the reels,” says Solano, “rewind it through the rereeling machine and twist it into skeins of raw silk.”
About three-fourths of a cocoon can be reeled the remainder in surface floss and husk. The reelable portion of cocoons ranges from 500 to 1,200 meters in length. The thread is usually thicker and stronger toward the middle of the reeled portion than at the end . One can produce one pound of silk from 1,500 to 2,500 cocoons.
“To propagate silkworms we select big cocoons, open these and take out the pupae,” says Solano. “We usually get 100 males and females. A male pupa has horizontal segments running across its body; a female has two line indentations at its posterior end.
‘We place the pupae in a room with a temperature of 24 degrees centigrade. These turn into moths seven days later. We let the months mate immediately. This takes four to five hours. After this, we separate the males and burn them. We put the females on sheets of bond paper and cover each with a funnel made of galvanized iron to prevent it from scattering its eggs. A moth produces 450 to 500 eggs each time it lays, Egg laying takes 12 hours after which we remove the funnels and burn the female moths. Fifty-four hours later we refrigerate the eggs at five degrees centigrade.”
To increase cocoon production, a new silkhouse is being built. It is designed to accommodate 180,00 worms,. In addition, more mulberry cuttings are being planted to increase leaf production.
The center has been conducting training sessions on sericulture methods since May 1974 and has, so far, oriented 94 individuals in all the phases of sericulture. At the end of each training period, all the participants are given mulberry cuttings so they can launch their own projects.
“We plan to convince people in other parts of the country to go into sericulture,” says bartlome.
Recently , PTRI opened another center in Cagayan de Oro city. And the Bureau of Plant Industry is now propagating mulberry cuttings in NOvaliches, Quezon City.
Source: Greenfields, 1976