Tussah originated in south-central Shandong Province, China, and its cocoon silk output is second only to that of silkworm. Tussah owners are mainly distributed in Liaoning, Shandong, Henan, Jilin, Heilongjiang, Inner Mongolia, Shanxi, Guizhou, Sichuan and other provinces, and there are also many countries such as Japan, South Korea, India and North Korea. It can be said that tussah is a characteristic industry in China. The annual output of tussah cocoons has reached 70,000 tons, of which the output of tussah in Liaoning Province accounts for 80% of the national share and 70% of the world share.
Four forms of tussah
Tussah is a completely deformed insect. In its 28 days, it experienced four forms: egg, larva (silkworm), pupa and adult (moth). It overwinters as a pupa.
(1) egg stage
Egg stage is the stage of embryo development and larval formation from fertilization to hatching. A fertilized egg is an egg fertilized by a mother moth and combined with sperm nucleus 150min(25℃) to form a fertilized egg. After the fertilized egg is formed, it begins to divide, producing many subnuclei, which move to the periphery of the egg, forming a monolayer cell embryo centered on each nucleus. The cells on one side of the ovule hole of the blastoderm thicken to form an embryonic zone, and then through the stages of germ layer differentiation and organ formation, larvae are formed and hatched.
(2) Larval (silkworm) stage
Larval stage is a feeding growth stage from hatching to pupation. Tussah larvae usually go through four growth molting and five growth stages. 1~3 instar larvae are called young silkworms, 4~5 instar larvae are called sleeping silkworms, and newly molted larvae are called present silkworms. At the end of 5th instar, the larvae stopped eating oak leaves, and their bodies were shortened to mature silkworms. Mature silkworms spin silk and form cocoons, and soon become pupae through morphological degradation and molting.
(3) Pupal stage
From pupa to emergence, it is the metamorphosis stage from larva to adult. The pupa's appearance remains the same, but its body is changing dramatically. The tissues and organs of larvae are free in the early pupa stage, and the tissues and organs of adults are formed in the middle and late pupa stage.
(4) Adult (moth) stage
The adult stage is from emergence to death, when sexual maturity mates, lays eggs and reproduces. In the later stage of pupa, the tissues and organs of adults form and then emerge into adults. Adults spit out weak alkaline liquid and cocoon-dissolving enzyme from their mouths, dissolve the cocoon head and then drill out. The female moths mate, fertilize and lay eggs, and then the silkworm moths die on their own in about 14 days, ending their lives.