🐛 Life Cycle of Philosamia ricini (Eri Silkworm)

Philosamia ricini, commonly known as the Eri silkworm, is a domesticated, multivoltine species used for producing Eri silk, a type of non-mulberry silk. It belongs to the family Saturniidae and is native to the northeastern and eastern regions of India. Unlike Bombyx mori, Eri silk is spun and not reeled, as the pupa is not killed during silk harvesting, making it Ahimsa silk (peace silk).

The life cycle of Philosamia ricini comprises four main stages: egg, larva, pupa, and adult moth. The complete cycle takes about 44–50 days, depending on environmental conditions.

🥚 1. Egg Stage: Female moths lay about 300 to 500 oval eggs on leaves or paper strips.  The eggs are creamy white and slightly larger than those of Bombyx mori. Under optimal temperature (25–28°C) and humidity (70–80%), the eggs hatch in 6–10 days. Hatching larvae are small and dark in color.

🐛 2. Larval Stage

The larval stage lasts for 15–20 days and includes five instars (molting stages). Eri larvae are polyphagous, meaning they feed on various host plants such as: Castor plant (Ricinus communis) – primary food source,  Kesseru (Heteropanax fragrans) and Payam (Evodia flaxinifolia). The mature larva is robust, creamy white with fine hair, and grows up to 8–10 cm in length. The silk glands develop during this phase and prepare the larva for cocoon spinning.

🧵 3. Pupal Stage (Cocoon Formation)

After reaching full size, the larva stops feeding and begins spinning a loose, open-ended cocoon around itself using coarse silk fibers. Unlike Bombyx mori, the cocoon is not compact and allows the moth to emerge without damaging the silk, hence suitable for spun silk production. The pupa develops inside the cocoon over 12–15 days, depending on temperature and humidity.

🦋 4. Adult Moth Stage

Adult moths are large, hairy, and brownish-white with reddish or gray markings on the wings.They emerge easily from the open-ended cocoon without the need for stifling.The adult lifespan is 5–7 days, during which mating and egg-laying occur.Moths do not feed; their primary purpose is reproduction.

🌿 Environmental Adaptability

Philosamia ricini is highly suited for: 

• Tropical and subtropical climates

• Regions with abundant castor plantations

• Year-round cultivation due to its multivoltine nature (up to 6–8 broods annually)

This adaptability makes it especially popular in Assam, Meghalaya, Nagaland, Odisha, and Andhra Pradesh.

📊 Summary Table

 

Stage	Duration	Description
Egg	6–10 days	Creamy white, oval eggs laid on leaves or paper
Larva	15–20 days	Feeds on castor and other host plants; 5 instars
Pupa	12–15 days	Inside a soft, open-ended cocoon; no stifling needed
Adult Moth	5–7 days	Large moth, mates and lays eggs, does not feed

Key Differences from Bombyx mori

Feature	Bombyx mori	Philosamia ricini
Silk Type	Reeled silk	Spun silk (Ahimsa silk)
Host Plant	Mulberry (Morus alba)	Castor and other leaves
Cocoon Structure	Closed, compact	Loose, open-ended
Use of Pupa	Usually killed (for silk)	Allowed to emerge
Commercial Name	Mulberry Silk	Eri Silk

📚 References

1. Ganga, G. & Sulochana, C. (1997). An Introduction to Sericulture. Oxford & IBH Publishing.

2. Srivastava, P.N. (2012). Textbook of Sericulture. Kalyani Publishers.

3. Central Silk Board India – https://csb.gov.in

4. FAO Sericulture Manual. (1999). http://www.fao.org

5. Bhattacharya, A. (2005). Eri Silk – A Potential Sericulture Enterprise for Tribal Development. Indian Journal of Traditional Knowledge.