Wild Silk Production: Cocoon Quality and Host Plant Influence

Last Updated: January 28, 2026
Estimated reading time: ~7 minutes
Word count: 1,290

The economic viability of wild silk production—encompassing Tasar, Fagara, and Moon moth silks—hinges on the quality and quantity of the cocoons harvested. While traditional sericulture focuses on Bombyx mori, the “Vanya” or wild silk sector relies on Saturniid moths like Antheraea mylitta, Attacus atlas, and Actias selene. This detailed analysis explores the commercial parameters of wild silkworm cocoons, evaluating how specific host plants and new subspecies variances directly impact silk yield, shell ratio, and filament denier, based on biosystematic studies from Western Maharashtra.

Key Takeaways

• Superior Shell Ratio: Attacus atlas cocoons demonstrated the highest shell ratio (19.32%), indicating significant potential for spun silk (“Fagara”) production.
• Host Plant Hierarchy: Terminalia tomentosa consistently yielded heavier cocoons and higher shell ratios compared to Terminalia arjuna and Terminalia catappa.
• Subspecies Variation: New Antheraea mylitta subspecies exhibit wide denier variation, from fine (8.28 in jujubi) to coarse (13.89 in sathei).
• Alternative Hosts: Terminalia catappa proved to be a commercially viable host, producing cocoons with satisfactory shell weights (~1.09 g) for indoor rearing.
• Silk Quality: The study characterizes wild silk not just by weight but by “denier” (fiber thickness), crucial for textile applications.

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Quantitative Analysis of Wild Silk Production

Defining Cocoon Quality Metrics

To standardize wild silk production, sericulturists must look beyond simple survival rates and analyze the physical properties of the cocoon. The thesis establishes a framework for characterizing these “yield attributes,” which determine the market value of the silk.

Key Metrics Evaluated

1. Single Cocoon Weight (SCW): The total weight of the pupa and the silk shell. This indicates the general health of the larva.
2. Shell Weight (SW): The weight of the silk layer alone after removing the pupa. This is the raw economic yield.
3. Shell Ratio (SR%): Calculated as $(Shell Weight / Cocoon Weight) \times 100$. A higher percentage means more silk per unit of biological effort.
4. Filament Length & Denier: The total length of the reelable silk thread and its thickness. Denier is a unit of linear mass density of fibers.

“The qualitative and quantitative characters of the cocoon greatly vary and much depends upon the type of food plants used… The commercial Character of both male and female cocoons when reared on primary food plants indicate that the cocoons of A. selene are having sericultural importance.” (Kavane, 2010, p. 198-199)

Student Note: Denier is a measure of fiber thickness. A lower denier number (e.g., 8) implies a finer, more delicate silk, while a higher number (e.g., 12+) indicates a coarser, more durable fiber often used in furnishing fabrics.

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Performance of Antheraea mylitta Subspecies

One of the most significant contributions of this research is the quantitative profiling of nine newly identified subspecies of the Indian Tasar silkmoth (Antheraea mylitta). These subspecies, found in diverse ecological pockets of the Western Ghats, show distinct commercial traits that can be exploited for specific breeding programs.

Yield Comparisons

• High Yielders:
  • A. mylitta sahyadricus: Produced significantly heavy cocoons with a shell ratio of 11.76% and a denier of 8.96.
  • A. mylitta sathei: Exhibited a very high denier of 13.88, suggesting it produces exceptionally strong, thick silk fibers suitable for heavy textiles.
• Fine Silk Producers:
  • A. mylitta jujubi: Recorded a denier of 8.28 and a shell weight of 0.95 g.
  • A. mylitta indica: Showed a denier of 8.31 with a filament length of 292 meters.

These variations suggest that rather than relying on a generic “Tasar” stock, sericulturists can select specific subspecies to target different sectors of the textile market (fine sarees vs. upholstery).

Fig: Cocoon Parameters of Select New Antheraea mylitta Subspecies

Subspecies	Cocoon Weight (g)	Shell Weight (g)	Shell Ratio (%)	Denier
A. m. indica	8.42	1.12	13.30	8.31
A. m. jujubi	9.42	0.95	10.08	8.28
A. m. arjuni	10.42	1.20	11.51	11.04
A. m. kolhapurensis	9.35	1.40	14.97	8.81
A. m. sathei	11.42	1.65	14.44	13.88

Professor’s Insight: The A. mylitta kolhapurensis subspecies is particularly notable for its high Shell Ratio (14.97%), making it a prime candidate for commercial exploitation in the Maharashtra region.

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thesis quotes remain cited; remaining content is original and educational.

Impact of Host Plants on Silk Yield

The nutritional quality of the host plant leaves is the single most important factor influencing wild silk production. The thesis compared the cocoon metrics of silkworms reared on three primary hosts: Terminalia arjuna (Arjun), Terminalia tomentosa (Asan), and Terminalia catappa (Indian Almond).

Comparative Results

• Terminalia tomentosa (Asan): Consistently produced the best results. For A. selene (Moon moth), rearing on Asan yielded a shell ratio of 16.88% and a shell weight of 1.41 g.
• Terminalia arjuna (Arjun): Performance was slightly lower but still commercially viable. A. mylitta kolhapurensis reared on Arjun yielded a shell ratio of 11.66%.
• Terminalia catappa (Indian Almond): Although considered a tertiary host, it supported successful cocoon formation. A. selene reared on T. catappa produced cocoons with a 12.53% shell ratio.

Implications for Production

While forest-based T. tomentosa yields the highest quality silk, T. catappa offers a unique advantage: it is abundant in urban and semi-urban areas. This allows for wild silk production to extend beyond deep forests into accessible indoor rearing facilities, utilizing readily available fodder.

Fig: Effect of Host Plant on Actias selene Cocoon Quality

Host Plant	Cocoon Weight (g)	Shell Weight (g)	Shell Ratio (%)
T. tomentosa (Asan)	8.35	1.41	16.88
T. arjuna (Arjun)	8.05	1.20	14.90
T. catappa (Badam)	7.42	0.93	12.53

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Non-Tasar Wild Silks: Atlas and Moon Moth Potential

Beyond the traditional Tasar moth, the thesis highlights the untapped potential of other Saturniids.

Attacus atlas (Fagara Silk)

The Atlas moth produces a distinct silk known as “Fagara.” The study found that A. atlas spins an open-type cocoon (lacking a continuous filament for reeling), which is ideal for spinning like cotton or wool.

• Outstanding Metric: It achieved a massive Shell Ratio of 19.32%, the highest among all species studied.
• Production: A single cocoon contributes 1.82 g of shell weight. The silk is noted for its durability and light brown/tan color.

Actias selene (Moon Moth Silk)

Often ignored in sericulture, the Moon moth showed promising traits. Its cocoon is reelable, though the filament is not as continuous as Tasar.

• Quality: The silk is whitish-grey. The study confirmed that pure, white, and lustrous silk can be obtained from A. selene, especially when reared on T. tomentosa.

Professor’s Insight: While A. atlas cocoons cannot be reeled into a single thread due to their open structure (peduncle), their high silk mass makes them perfect for spun silk industries, which blend short silk fibers into yarn.

Real-Life Applications

1. Textile Product Diversification: The distinct denier values of the new subspecies allow the textile industry to categorize wild silks for specific uses—fine silk for garments (jujubi variety) and coarse silk for furnishing (sathei variety).
2. Urban Sericulture: Validating Terminalia catappa as a productive host plant enables small-scale silk farming in villages and towns, reducing dependency on forest rights and access.
3. Genetic Breeding Stock: The identification of high-SR% ecoraces like kolhapurensis provides valuable genetic material for breeding programs aimed at improving the national silk yield.
4. Waste Silk Utilization: The high shell weight of Attacus atlas supports the development of a “spun silk” cottage industry, utilizing cocoons that cannot be reeled.

Why this matters: Quantitative characterization transforms wild insects from forest curiosities into measurable economic resources, providing a scientific basis for pricing and grading wild silk.

MCQs

1. Which Antheraea mylitta subspecies recorded the highest denier value (coarsest silk) in the study?
A) A. mylitta indica
B) A. mylitta sathei
C) A. mylitta jujubi
D) A. mylitta kolhapurensis
Correct Answer: B
Difficulty: Moderate
*Explanation: According to the descriptions in the thesis results, *A. mylitta sathei* has a denier of 13.88 (or ~14), indicating very thick silk fibers.*

2. Which host plant consistently produced the highest Shell Ratio (%) for both A. selene and A. mylitta kolhapurensis?
A) Terminalia catappa
B) Ziziphus jujuba
C) Terminalia tomentosa
D) Ficus carica
Correct Answer: C
Difficulty: Easy
*Explanation: Tables 5 and 6 consistently show that *T. tomentosa* (Asan) yields the highest shell ratios (16.88% and 13.66% respectively).*

3. What is the distinguishing feature of the Attacus atlas cocoon that affects its processing?
A) It is white and soft.
B) It has a peduncle and is open-type.
C) It has the lowest shell weight.
D) It is double-layered and green.
Correct Answer: B
Difficulty: Moderate
*Explanation: The thesis notes that *A. atlas* spins an open-type cocoon with a long stalk (peduncle), making it suitable for spinning rather than reeling.*

4. How is the Shell Ratio (SR%) calculated?
A) (Cocoon Weight / Shell Weight) × 100
B) (Shell Weight / Pupa Weight) × 100
C) (Shell Weight / Cocoon Weight) × 100
D) (Pupa Weight / Shell Weight) × 100
Correct Answer: C
Difficulty: Easy
Explanation: Shell Ratio is the percentage of the total cocoon weight that is actual silk shell.

FAQs

Q: What is “Fagara” silk?
A: Fagara silk is the name given to the silk produced by the Atlas moth (Attacus atlas). It is durable, light brown/tan, and typically spun rather than reeled.

Q: Does Terminalia catappa produce good quality silk?
A: Yes, while slightly lower in yield than primary forest hosts, T. catappa produces commercially acceptable cocoons (Shell Ratio ~10-12%) and is viable for indoor rearing.

Q: Why is Denier important in wild silk production?
A: Denier measures the thickness of the silk filament. Knowing the denier helps weavers decide whether the silk is suitable for delicate saris (low denier) or heavy drapes and upholstery (high denier).

Q: Which wild silkmoth had the highest overall silk content per cocoon?
A: The Atlas moth (Attacus atlas) had the highest Shell Ratio (19.32%) and a very high single shell weight (1.82 g), making it a heavyweight in silk production potential.

Lab / Practical Note

Calculating Shell Ratio: In the lab, weigh the whole cocoon (with pupa) first ($W_c$). Then, cut the cocoon open, remove the pupa and shed larval skin, and weigh only the silk shell ($W_s$). Use the formula $\text{SR\%} = (W_s / W_c) \times 100$. Ensure cocoons are harvested on the 6th day after spinning to allow full drying and hardening.

External Resources

• International Sericultural Commission – Global data on silk statistics and wild silk varieties.
• ScienceDirect – Wild Silk Properties – Academic papers on the physical properties of non-mulberry silks.

Sources & Citations

Kavane, R. P. (2010). Biosystematics of wild silkmoths from Western Maharashtra. (Doctoral dissertation, Shivaji University, Kolhapur). 1-304.

Source Note: Cocoon metrics, weights, and ratios were derived from Tables 4, 5, and 6, and the taxonomic descriptions in Chapter IV.

Correction Invitation: If you are the author of this thesis and wish to provide updates or corrections to this summary, please contact us at contact@professorofzoology.com.