Understanding the Unique Needs of Chawki Worms in Sericulture

In sericulture, the quality of the final silk cocoon is determined not at harvest time, but in the very first days of a silkworm’s life. Silkworms pass through five developmental phases called instars before they are ready to spin cocoons, and the first two of those instars demand a level of care that is categorically different from everything that follows. These early-stage larvae – known as chawki worms – are so small, so delicate, and so sensitive to their environment that rearing them successfully is considered both an art and a science. Getting this stage right is not just about keeping the worms alive; it sets the trajectory for cocoon yield, silk quality, and the farmer’s profitability for the entire crop.

What are chawki worms? 🔗

Young silkworms up to the end of the second instar are called chawki worms. To the naked eye, they resemble tiny ants – dark-coloured, hairlike, and barely visible. This is not merely a descriptive observation; chawki silkworms are also commonly called “ant silkworms” because of how closely they resemble small brown ants at hatching. At this stage, Bombyx mori larvae are at their most fragile. Their bodies are small, their mouthparts are weak, their immune defences are minimal, and any mishandling – rough transfer, exposure to unfavourable temperatures, or a drop in leaf freshness – can lead to mortality or stunted growth.

The chawki phase typically spans about eight days, covering the first and second instars. Robust growth and development during the chawki stage makes silkworms more resistant to diseases and more stress-tolerant during the later stages of development. This is why so much focus in sericulture is placed on getting chawki management right.

Why chawki worms have unique environmental needs 🔗

Silkworms are cold-blooded organisms, which means their body temperature and physiological processes are directly governed by the environment around them. Maintaining the recommended temperature, relative humidity, light, and ventilation for every stage of rearing is of utmost importance for successful silkworm production. For chawki worms specifically, these requirements are more demanding than for older larvae.

Temperature and humidity requirements 🔗

A temperature of 27-28°C and a relative humidity (RH) of 80-85% is required for first and second instar larvae. These figures are noticeably higher than what is recommended for third to fifth instar worms (24-25°C and 60-65% RH). The higher humidity is not incidental – it serves a critical function. Chawki worms receive all of their moisture through the leaves they eat. If the rearing environment becomes too dry, leaves wilt and lose succulence, and the worms, unable to compensate, become dehydrated quickly. The tiny larvae have to eat within four hours of hatching, or they die of dehydration – a stark reminder of how little margin there is for error at this stage.

For maintaining the temperature and humidity, a small and compact room is required to rear young age silkworms. This smaller space is easier to control and keeps conditions stable. Unnecessary opening of doors should be avoided, as it causes fluctuations in both temperature and humidity and increases the risk of contamination.

The wrap-up rearing method 🔗

One of the most effective techniques for maintaining the microclimate around chawki worms is wrap-up rearing. Worms are maintained on a paraffin paper in the rearing tray, and after feeding, the bed is covered with another sheet of paraffin paper, with the edges of both sheets folded together – this is what is meant by “wrapping up.” Where paraffin paper is unavailable, polythene sheets of 400 gauge thickness can be used. This wrapping traps moisture around the leaves and worms, preventing the rapid drying that ambient air would otherwise cause. All chawki rearing methods aim to prevent the drying of mulberry leaves by maintaining proper temperature and humidity in the rearing bed.

Leaf quality: the cornerstone of chawki rearing 🔗

The food a chawki worm receives is inseparable from its health outcome. Being too small and tender, young silkworms feed only on the surface of mulberry leaves. They require tender, soft, and succulent leaves with around 80% moisture content and high nutritive value. Mulberry leaves with approximately 27% protein, 11% carbohydrates, along with minerals and vitamins, are considered good for rearing.

Selecting the right leaves from the shoot 🔗

Not all mulberry leaves on a shoot are equal. On a mulberry shoot, the four leaves below the largest glossy leaf are well suited for first instar larvae, and the next four leaves below those are suitable for second instar worms. This means the farmer must actively identify and select leaves by position, not just pluck whatever is most convenient. Young larvae have small, weak mouthparts and cannot chew coarser leaves effectively. Feeding them mature or hardened leaves results in poor feeding rates, delayed moulting, and elevated mortality. Mulberry varieties like S-36 and V-1 are commonly preferred for chawki gardens because of their superior moisture content and leaf tenderness.

Leaf preparation and feeding schedule 🔗

Because chawki worms feed on the surface of leaves rather than chewing through them, the size of leaf pieces offered must be appropriate for their stage. Chopped leaves of about 1 cm² size are provided at the start of chawki rearing to facilitate the tiny worms in reaching the leaf surface quickly. As the worms grow in size, the leaf pieces can be gradually increased. Chopping also has a secondary benefit: it loosens the bed and helps dry it out during aeration, reducing the build-up of pathogens.

Leaf harvest must be done in the morning and evening, and the leaves preserved in a cool place covered with wet gunny cloth. In dry seasons, sprinkling water over stored leaves and keeping them under damp cloth helps retain moisture. Silkworms are fed three to four times a day depending on the climate, with the general practice being three feedings per day at 8:00 am, 2:00 pm, and 8:00 pm.

Managing moulting in chawki worms 🔗

Moulting is the process by which silkworms shed their old skin to allow for continued growth. It occurs four times across the larval period. During chawki rearing, two moults take place – at the end of the first instar and at the end of the second instar. During moulting, the larvae stop feeding and become inactive; special care is required for the moulting worms.

Feeding should stop when more than 90% of worms have settled for moult, and should resume only when 95% of worms have come out of moult. During the moult period, the polythene or paraffin cover is removed to allow aeration. Temperature and humidity should be kept slightly lower during moult – around 26°C and 65-70% RH – to ensure a dry bed that reduces the risk of disease. Lime powder is sometimes dusted on the bed to absorb excess moisture. Disturbing worms while they are moulting – whether by feeding or physical handling – can cause them to fail the moult and die, which is why this period requires restraint as much as active intervention.

Sanitation and bed management 🔗

Because chawki worms are highly susceptible to bacterial and viral infections, hygiene during this stage is not optional – it is a primary defence. Bed cleaning is done once in the first instar and twice in the second instar. Cleaning nets are placed over the bed, fresh chopped leaves are fed on top, and the worms – which naturally crawl upward toward food – are transferred to a new tray after about two hours, leaving litter and leftover material behind. If cleaning nets are not available, the topmost layer with worms can be carefully lifted with a feather.

Bed disinfectants should be dusted to avoid secondary contamination – around 50g after the first moult and 100g after the second moult for every 100 disease-free layings (dfls). Overcrowding is another risk to manage actively. Uniform distribution of larvae in the bed is essential; crowded conditions lead to uneven growth, poor feeding, and higher disease transmission. Hands must be washed with disinfectant solution before entry into the rearing house, after picking diseased worms, and after bed cleaning.

The case for centralised chawki rearing 🔗

Given the intensity of care required during the chawki stage, many sericulture programmes in India promote the concept of community chawki rearing centres (CRCs). The concept of community chawki rearing under expert supervision and special care is being promoted, with a viable centre rearing from 2,500 to 5,000 layings per batch over a period of eight days. This model allows individual farmers – who may lack the infrastructure or expertise to maintain precise environmental controls – to receive healthy, well-developed second instar larvae ready for late-age rearing on their own farms. The rearing practices of young worms in chawki centres are completely different from late age rearing and require a controlled environment that most small farmers cannot maintain independently.

The Karnataka Department of Sericulture and the Central Silk Board both provide standardised guidelines for chawki rearing, emphasising that the success of any cocoon crop is built on the foundation laid during these first eight days. When chawki rearing is done well – with the right leaf, the right environment, and strict sanitation – the worms that emerge from the second moult are robust, disease-resistant, and ready to deliver the silk yields that make sericulture economically viable.

What do you think? Given that chawki worms are so sensitive to leaf quality and microclimate, do you think most small-scale sericulture farmers have realistic access to the resources needed to rear them optimally on their own farms? And how might centralised chawki rearing centres be better integrated with individual farmer operations to close that gap?

References

1. https://www.agrifarming.in/silkworm-rearing-methods-beginners
2. https://egyankosh.ac.in/bitstream/123456789/9168/1/Unit-2.pdf
3. https://www.wormspit.com/tinymasters.htm
4. https://dacollege.org/uploads/stdmat/seri-sem-II-Unit-I-CSB-MODEL-REARING-HOUSE.pdf
5. https://wikieducator.org/Silkworm_Rearing
6. https://connectjournals.com/file_full_text/1792802H_657-665.pdf
7. https://karunadu.karnataka.gov.in/Sericulture/english/Pages/Chawki-Rearing.aspx
8. https://silks.csb.gov.in/anjaw/wp-content/themes/Common_District/trs-frame.html