My weaving instructor has a bag of silk coccoons waiting to be boiled
the cocoons rattle when shaken because the worm is shriveled up and dead
inside. So cocoons themselves keep well long after the worm is a moot
point. A live worm in the cocoon is not a necessity for silk
production, but its my understanding that the worms body, in one form or
another still needs to be inside because creating an opening for the worm
runs the risk of tearing the fiber and makes silk strand production even
Continuous strands of silk for production are created when the cocoon
(with worm alive or dead) is boiled and the strand teased and drawn out
of the water using a stick. The entire length of the resulting fiber is
actually a varying degree of fine to coarse (fine being interior and
coarse being exterior, I believe. It could be the other way. I havent
done a lot of heavy studying on silk yet). The quality of the fiber is
based on the point the worm is at in spinning his cocoon and is based on
its metabolism as it winds out. So one end of any complete strand of
just boiled silk will be coarse and the other will be fine (relative to
the strand, not to other fibers).
As for the animal husbandry aspect of it, I imagine that it is possible
that there may be a way to harvest only the best specimens and keep them
in an environment more favorable for becoming moths, but if you think
about it, most caterpillars the world over dont make it from cocoon to
wings. Temperature, worm health and disease would play a big part into
it, I believe. A frost, a heat wave, a sudden storm and its all over.
Otherwise, the moths wouldnt need to lay several hundred eggs at a time.