This slide share helps the sericulturist to maintain favourable environmental conditions for silkworm development and also to prevent disease attack as silkworms are delicate and sensitive to the environmental factors prevailing during silkworm rearing.

1. MAINTENANCE OF
ENVIRONMENTAL CONDITIONS
DURING REARING OF
SILKWORMS
KUNTAMALLA SUJATHA M. SAI ABHISHEK
Asst Prof., Sericulture Department, Project Officer,
Kakatiya University, BDL,
Hanamkonda, Warangal. Hyderabad.
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Dr. Kuntamalla Sujatha & M. Sai Abhishek

2. ENVIRONMENTAL CONDITIONS
The development of silkworm larvae and cocoon quality is effected by
environmental conditions such as temperature, humidity, light and air current. But the
influence of these conditions is not uniform during rearing period chawki period it requires
26 – 28, while during late age rearing it requires a temperature of 23 – 25o C. hence it is
needed to provide favourable climatic condition suitable for different stages.
Environmental conditions include –
1. Temperature
2. Humidity
3. Air
4. Light
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Dr. Kuntamalla Sujatha & M. Sai Abhishek

3. TEMPERATURE
Silkworm is a cold blooded organism which changes its body temperature. Temperature
influences the metabolic rate, enzyme activities, nutrient conversion, digestion,
assimilation, absorption, excretion and other physiological activities. The silkworm can be
grown in temperature varying from 15o C to 40o C by in-view of its effect on the
physiology of silkworm it is divided into three groups. 20 - 25o C  it is harmless for
silkworm growth. By higher and lower temperature than this range affects the physiological
activities of the silkworm. 23 - 28o C  favourable for healthy growth of late – age
silkworms. 26 - 28o C  good quality of cocoon. If temperature is raised above optimum
temperature  larval duration is shortened, low temperature  prolongation of larval
duration. If temperature is decrease in early age it  retards physiological activities 
worm do not feed  leads to starvation  weak worms  susceptible to diseases  poor
cocoon quality.
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4. Age Optimum temperature
1 27 – 28o C
2 26 – 27o C
3 25 - 26o C
4 24 - 28o C
5 23 - 24o C
Hence temperature during the early age should be higher than the late age worms.
IDEAL TEMPERATURE
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5. Regulation of temperature
Temperature varies according to seasons and places.
If lower temperature  temperature is raised with help of electric heaters or oven or charcoal
stoves.
•Charcoal stoves cause air pollution. It is better to use live cylinder covered with layer of ash
for better, regulated and uniform distribution of heat.
•Proper designing of rearing house can mitigate the higher temperature, hence it is always
advised to build the rearing house in North and South direction.
•In villages during summer, the windows are to be kept open at night while the doors and
windows are to be closed during day time or the doors and windows are to be opened during
early morning so the cool air from outside flows into the rearing room and brings the
temperature.
•Wet gunny cloths are hung to doors and windows to bring down the temperature.
•Air coolers or air conditioner, regulate the temperature, can be used by private rearer. But
not feasible for marginal Indian farmers.
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6. HUMIDITY
•The second climatic condition which is useful is the humidity which also effect the growth
and health of silkworm. High humidity causes prolongation of the rearing period by
accelerating the physiological activities leading to prolongation of the larval duration. The
pH value of blood is remarkably lower at high humidity than low humidity conditions.
•Humidity is increased by expiration of CO2 and evaporation.
Low humidity prolongs the length of growing period. The role of humidity is direct and
indirect.
•The optimum humidity for silkworm growth is 70 - -75%. Early instars are resistant to high
humidity, late age worms cannot withstand high temperature and humidity.
•In an extremely desiccated rearing room  the silkworm cannot eat mulberry leaves that
has withered  they become malnutritious humidity.
•When rearing house is humid it becomes favourable for pathogenic microbes and thus the
silkworms are affected by diseases.
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7. Age of worms Humidity %
1 90 – 95 %
2 85 – 90 %
3 80 – 85 %
4 75 – 80 %
5 70 – 75 %
The humidity is recoded using hydrometer or dry and wet bulb thermometer
along with a conversion chart is used.
DIFFERENT HUMIDITY
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8. Regulation of humidity
• Humidity changes from season to season and also within the day during certain seasons.
• Regulation of humidity is very necessary can be done using adapting box rearing
method and also by using paraffin papers and wet foam pads or wet news paper around
the rearing seat.
• Care is taken not to wet the feacal matter which can lead to occurrence of diseases.
• The humidity during moulting is also needed to be maintained in a proper way to avoid
unique and disease occurrence.
• If temperature is high, humidity has to be increased. If the leaves wither they can be
sprinkled with water or stored in leaf chamber.
• Humidity can also be increased by wetting the soil below the sand that is placed under
the rearing stands, but not by filling the room floor with water.
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9. AIR:-
The nine pair of spiracles which are present in first thoracic and 8 abdominal segments on both
sides of the body supply O2 to blood through tracheae while CO2 and water formed is exhaled out.
In rearing house, the air is polluted due to accumulation of CO2 released by rearers and mulberry
leaves and formaldehyde gas from disinfectants and ammonia from litter.
The young silkworms are less resistant to toxic gases. During late ages they tolerate the toxic
substances more than chawki worms, hence it is important to ventilate this air out as these toxic
gases can affect the rearing process.
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10. Regulation of air
•Fresh air is comparatively heavier than polluted air, hence proper ventilation is needed
for good yield and quality cocoons.
•Hence care should be taken to remove paraffin paper one hour before rearing.
•Rotation of trays in rearing stands.
•Opening of windows.
•Construction of windows and door in proper alignment.
•Provision of 1.0 m / sec air during V age rearing reduces the larval mortality and
improves digestion, larval weight, cocoon weight, pupation when compared to poor
ventilation.
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11. LIGHT
•Silkworms are found of dim light of 15 – 30 lux so avoid strong light and darkness.
•Light influences the health and survival of silkworm but influences the distribution of
larvae  18 hrs of photo periods affects the cocoon quality and quantity, appetite is
improved.
•Silkworms are reared in dim light of 15 – 30 luxs during day time and under complete
darkness at night.
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