Japanese Tussah Silkworm

The Japanese Tussah silkworm, scientifically known as Antheraea yamamai, is a remarkable insect valued for its silk-producing capabilities. Unlike its domesticated counterpart, the mulberry silkworm, the Tussah silkworm thrives in wild, natural environments, predominantly in regions of China, Japan, and North Korea. This article delves into the life cycle, characteristics, and unique properties of this intriguing creature.

1. Life Cycle of the Japanese Tussah Silkworm

The Japanese Tussah silkworm undergoes complete metamorphosis. The following table outlines key stages and their approximate durations:

2. Adult Moth Characteristics

• Emergence: Adult moths typically emerge in August, with the emergence period spanning over 30 days. Optimal temperature for emergence is between 22-26°C. Males emerge earlier than females.
• Size & Appearance: The wingspan ranges from 12 to 15 cm. Females are larger, about 4.5 cm long, while males are around 3.7 cm. Moths exhibit varied colors, including orange, grey, auburn, red, tea, and blue.
• Mating: Mating usually takes place between midnight and 3 am. The ideal environment for mating is quiet, dark, cool (around 18°C), with high humidity (around 90%) and low ventilation. Orange-yellow moths have the highest mating rate. Artificial mating is difficult.
• Egg Laying: Female moths lay eggs on side branches, typically in clusters of 10-20, with each moth laying 150-250 eggs. Embryos develop into ant silkworms in about a week but overwinter in their egg shells.

3. Egg Characteristics

The eggs are dark brown with a strong, dark brown glue coating over a milky white shell. They are flat and oval-shaped, measuring approximately 280-290 mm in long diameter and 250-280 mm in short diameter. Weighing approximately 120-140 eggs per gram, the eggs have a thick shell (3-4 times thicker than mulberry silkworm eggs) and can withstand temperatures as low as -20°C.

4. Larval Development

• Hatching: Larvae hatch in early to mid-May in Northeast China. The ideal temperature for hatching is 18°C, with 75-85% relative humidity. Under these conditions, the hatching rate can reach around 90%.
• Appearance: The newly hatched ant silkworm weighs about 5-6 mg and is around 0.76 cm in length. It’s yellow-green with five black-cyan body lines. Larvae undergo color changes, becoming green by the third instar.
• Growth: The 5th instar larva weighs 17-20 grams, reaching lengths of 7-9 cm. Larval body weight increases approximately 4,000 times during development.
• Diet: The larvae primarily feed on Tussah plant leaves, such as Liaodong Tussah, Mongolia Tussah, and Acephalocustria leaves.

5. Silkworm Rearing and Disease Management

• Natural Rearing Challenges: In the wild, silkworms face numerous natural enemies, resulting in a cocoon formation rate of only about 35%.
• Indoor Rearing: To combat natural predators, young silkworms can be raised indoors, fed fresh branches with leaves. Ideal conditions include temperatures of 25-28°C, 70-75% humidity, and appropriate water supply.
• Disease: Common silkworm diseases include pussy, softening, particle, and sclerosis, with softening disease being the most prevalent. Germplasm-related diseases and environmental factors contribute to disease. Disinfection of egg surfaces and improved rearing techniques can help reduce disease incidence.
• Behavior: Larvae are solitary and tend to scatter. Older larvae (3-5 years old) tend to crawl more frequently, especially in hot or dry conditions. It is crucial to raise them in environments with fresh feed, ample moisture, low temperatures, and good ventilation. Larvae drink after rainfall and, in dry weather, benefit from morning or evening water spray. They also tend to eat their molted shells.

6. Cocoon Formation and Characteristics

• Cocooning: At the end of the 5th instar, the silkworm loses its appetite, its body shrinks, and it starts to spin a cocoon by wrapping itself in 2-3 tussah leaves. The cocoon has a thin floating silk layer and a stalk attaching to the leaf vein.
• Harvesting: Cocoons are harvested 7-8 days after cocooning. It’s best to harvest the cocoons still wrapped in leaves to minimize pupa damage.
• Cocoon Appearance: Cocoons are oblong, with a long diameter of 45-53 cm and a short diameter of 23-27 cm. They can be dark green, light green, or dark golden yellow but most are green with darker and lighter sides. Captive cocoons tend to be yellow-green.
• Cocoon Weight: Female cocoons weigh around 8 grams, while male cocoons weigh approximately 6 grams. Female cocoon layers weigh about 0.7 grams, while male cocoon layers are about 0.6 grams. Female cocoon layer rate is around 8.8% and male cocoon layer rate is around 10%.
• Silk Properties: The silk from these cocoons is unique. One cocoon can yield 600-700 meters of silk. It is naturally beautiful, soft, and has a natural green color and luster. It is also thicker (5-6 denier) and stronger (2.5 times stronger than mulberry silk). It boasts an elongation of about 40-50% (1.8 times that of mulberry silk). It can be woven into gorgeous, high-class fabrics. The high quality of Tussah silk makes it ideal for blending with other fibers, offering manufacturers a unique material for luxury textiles.

The Japanese Tussah silkworm, a wild silk producer, offers a valuable alternative to the domesticated silkworm, particularly when sustainability and unique characteristics are considered. Its rearing and harvesting techniques differ, requiring knowledge of its natural environment and behaviors. The resulting silk is of exceptional quality, making it a sought-after material in the textile industry. PandaSilk, a well-known brand, is one of the leading producers of sustainable silk fabrics, including Japanese Tussah.