D  
  
 
 Reference number  
DRS 357: 2017  
© RBS yyyy 
© RSB 2017  
 
 RWANDA 
STANDARD  DRS 
357 
 
First edition  
2017 -mm-dd 
 
Silk cocoon production  — Code of practice  
  DRS 357: 2017  
©RSB 2017  All rights reserved                  ii 
 
 In order to match with technological development and to keep continuous progress in industries, 
Standards are subject to periodic review. Users shall ascertain that they are in possession of the latest 
edition  
 
 
 
 
 
 
 
 
 
 
© RSB 2017  
All rights reserved. Unless otherwise specified , no part of this publication may be reproduced or utilized 
in any form or by any means, electronic or mechanical, including photocopying and microfilm, without 
prior written permission from R SB. 
Requests for permission to reproduce this document should be  addressed to  
Rwanda Standards  Board  
P.O Box 7099 Kigali -Rwanda  
KK 15 Rd, 49  
Tel. +250 252 586103/582945  
Toll Free: 3250  
E-mail: info@rsb.gov.rw  
Website: www.rsb.gov.rw  DRS 357: 2017  
iii                 ©RSB2017  All rights reserved  
 
 Contents  Page 
Foreword  ................................ ................................ ................................ ................................ ...................  iv 
1 Scope  ................................ ................................ ................................ ................................ .............  1 
2 Terms and definitions  ................................ ................................ ................................ ..................  1 
3 Requirements  ................................ ................................ ................................ ................................  3 
3.1 General  ................................ ................................ ................................ ................................ ..........  3 
3.2 Specific requirements  ................................ ................................ ................................ ..................  3 
3.2.1  Major requirements  ................................ ................................ ................................ ......................  3 
3.2.2  Minor requirements  ................................ ................................ ................................ ......................  7 
3.2.3  Recommendations  ................................ ................................ ................................ .......................  8 
4 Assessment  Criteria  ................................ ................................ ................................ .....................  9 
Annex  A (informative)  Illustration of silk cocoon  ................................ ................................ ...............  10 
Bibliography  ................................ ................................ ................................ ................................ .............  18 
 DRS 357: 2017  
©RSB 2017  All rights reserved                  iv 
 
 Foreword  
Rwanda Standard s are prepared  by Technical Committees and approved by R wanda Standards Board (RSB) 
Board  of Directors in  accordance with the procedures of RSB, in compliance with Annex 3 of the WTO/TBT 
agreement on the preparation, adoption and application of standards.  
The main task of technical committees is to prepare national standards.  Final Draft Rwanda S tandards adopted 
by Technical committ ees are ratified by me mbers of RSB Board of Director s for publication and gazettment as 
Rwanda Standards.  
DRS 357 was prepared by Technical Committee RSB/TC 029, Textiles and Leather  Engineering , 
In the preparation of this standard, reference was made to the following standard  
Thai Agricultural Standard  TAS 8201 -2012  
The assistance de rived from the above source is hereby acknowledged with thanks.  
Committee membership  
The following organizations were represented on the Technical Committee on Textiles and Leather  Engineering 
(RSB/TC 029) in the preparation of this standard.  
C&H  
Consumer Association (ADECOR)  
National Agricultural Export Board (NAEB)  
National Industrial Re search Institute (NIRDA)  
Rwanda Development Board  (RDB)  
University of Rwanda - College of Science and Technology ( UR -CST)  
UTEXRWA  
Rwanda  Standards Board  (RSB) – Secretariat  
 DRS 357: 2017  
1                 ©RSB2017  All rights reserved  
 
 Silk cocoon production — Code of practice  
1 Scope  
This Draft Rwanda Standard  establishes the production practices for fresh cocoon made by silkmoth caterpillar  
(bombyx mori) , fed on mulberry leaves. This  standard covers every activity of production from the rearing house 
to transport in order to obtain  good quality silk  
2 Terms and definitions  
For the purposes of this standard, the follow ing terms and definitions apply  
2.1  
Young larva or young stage silkworm  
larva from hatched egg to the full grown third  instar larva. (the third pre -moulting silkworm )  
- First instar larva means la rva from hatched egg to before the first moulting. At this stage,  the larva feeds on 
mulberry leaves 3 to 4 days then stops eating and begins to moult (Figure A.1).  
- Second instar larva  means larva after the first moulting to before the second moulting. At  this stage, the larva 
feeds on mulberry leaves 2 to 3 days then begins to moult (Figure A.1).  
- Third instar larva  means larva after the second moulting to before the third moulting. A t this stage, the larva 
feeds on mulberry leaves 3 to 4 days then begins to moult (Figure A.1).  
- Moulting:  the manner in which an animal routinely casts off a part of its body (often, but not always, an outer 
layer or covering), either at specific times o f the year, or at specific points in its life cycle  
2.2 
Grown larva or grown stage silkworm  
means larva from the fourth to the fifth instar.  
- Fourth instar larva means larva after the third moulting to before the fourth moulting. At  
this stage, the larva feeds on mulberry leaves 3 to 4 days then begins to moult (Figure A.1).  
- Fifth instar larva  means larva after the fourth moulting to pupa stage. At this stage, the  
larva feeds on mulberry leaves 6 to 8 days (Figure A.1).   
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 2.3  
Pre-moulting silkworm  
fully grown larva at each stage, stops eating, and its skin  becomes lustrous and ready to moult by shedding its 
skin. This can be observed from the  connected part between head and thorax  (Figure A.2)  with triangular shape 
(Figure A.3 ). 
2.4  
Post -moulting silkworm  
larva after moulting and start eating. The characteristics can be  described by bigger head and paler colour than 
that of the pre -moulting silkworm. The skin is also  wrinkled (Figure A.4).  
2.5 
Mature silkworm  
fully grown silkworm at the fifth instar larva that is ready to form its  cocoon (Figure A.5).  
2.6  
Mounting frame or cocooning frame  
material on which cocoon is formed.  
2.7  
Cocoon  
the outer protective shell spun by silkworm larva covering itself before transforming into pupa stage. Usually, 
cocoon for the market consists of pupa and slough inside.  
2.8 
Fresh cocoon  
cocoon that consists of a live pupa, shell, and slough including cocoon  with and without de -flossing.  
2.9  
Good cocoon or normal cocoon  
cocoo n that shall be characteristic of its variety, free  of stains, and no rough shell, with live pupa, and well -
formed silk filament.  DRS 357: 2017  
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 2.10 
Defect cocoon or poor cocoon  
Defect cocoon or poor cocoon means cocoon whose shape is deviated from its variety characteristics or 
abnormal characteristics i.e. double cocoon (Figure A.6), pierced cocoon (Figure A.7), inside soiled cocoon 
(Figure A.8), outside soiled cocoon (Figure A.9), thin -shelled cocoon (Figure A.10), loose -shelled cocoon 
(Figure A.11), thin -ended cocoon (Figure A.12), malformed cocoon (Figure A.13), printed cocoon (Figure A.14), 
crushed cocoon (Figure A.15), and mouldy cocoon (Figure A.16).  
2.11  
Pebrine disease   
protozoan disease of the silkworm, Bombyx mori  L. caused mainly by Nosema bombycis  Naegeli and can be 
transmitted via silkworm eggs  
NOTE  This disease  is prohibited.  
3 Requirements  
3.1 General  
Requirements of good practices for silk cocoon production are classified into 3 levels as follows : 
a) Major requirements mean the mandatory provisions  that shall be complied with. In case of  non-compliance, 
it will directly or seriously affect the quality of silk cocoons. It also includes the  requirements under relevant 
laws and regulations  as per the Sericulture centre regulations . 
b) Minor requirements mean the provisions  that should be complied. In case of non  compliance,  it will indirectly 
affect quality of silk cocoons.  
c) Recommendations mean the provisions  that are recommended for practices to help achieve  the objectives 
of this Good Practices for Silk  Cocoon Production.  
3.2 Specific requirements  
Requirements of Good Practices for Silk Cocoon Production shall be as per clauses 3.2.1- 3.2.3. 
3.2.1  Major requirements   
3.2.1.1  Silkworm rearing  house  
3.2.1.1.1 Keep  distance from the area prone to risk causing adverse health effect on silkworms such as  area 
of pesticide application and air -polluted source. In case of risk, there shall be preventive measures in place.  
3.4.1 .1.2 Clean, and not be disease harbourage aff ecting the health of silkworms  
3.4.1 .1.3 Availability of good ventilation   
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 3.4.1 .1.4 Availability of adequate space for rearing silkworms  
3.4.1 .1.5 Availability of preventive measures for direct sunlight onto silkworms  
3.4.1 .1.6 Availability of preventive measures from rain  
3.4.1 .1.7 Availability of a treatment plan when pests attack the silkworms  
3.4.1 .1.8 Availability of preventive measures for disease carrying pests  
3.4.1 .1.9 Availability of preventive measures for pests of silkworms and cocoons e.g. Uzi  fly (Exorista  
bombycis Louis), spider, ant, lizard, gecko, and rat  
3.2.1.2  Production inputs  
3.2.1.2.1  Silkworm eggs  
3.2.1.2.1 .1 Eggs are from the source that female moths have been inspected and certified for the absence 
of pebrine disease.  
3.2.1.2.1 .2 Come from sources with good transport management, temperature not higher than 25 oC, 
relative humidity not less than 80%, and not be affected by light  
3.2.1.2.2  Third instar larva (in case that farmer does not rear the first and second instar larva)  
Silkworm eggs shall come from the source that female moths have been inspected and certified for the absence 
of pebrine disease. The preventive measures for disease in young larva rearing house shall be available . 
3.2.1.2.3  Mulberry leaves  
The mulberry plot shall be kept distance from the pesticide application area or air -polluted source. In case of 
risk, there shall be preventive measures in place . 
3.2.1.2.4  Moisture absorbent  
Availability of moisture absorbent e.g. lime and burned paddy husks (burned paddy husks shall be in their 
original raw shape, and not in powder)  
3.2.1.2.5  Cleaning agent and disinfectant  
Availability of effective cleaning agents and disinfectants for eliminating mould, bacteria, virus, and protozoa on 
equipment and rearing house  DRS 357: 2017  
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 3.2.1.2.6  Materials, tools and equipment  
3.2.1.2.6.1  Materials, tools and equip ment for silkworm rearing, mounting, and storage of mulberry leaves, 
e.g. feathers, rearing trays, leaf containers, knives, cutting board, flat baskets, mounting frames shall be clean 
and disinfected.  
3.2.1.2.6.2  Availability of nets or materials to enable  discarding silkworm excreta and to be appropriate to 
silkworm stages  
3.2.1.2.6.3  Any mounting frame shall be well ventilated and shall not cause silkworm waste accumulation 
affecting cocoon quality and efficiency of silk reeling.  
3.2.1.2.6.4  Cocoon contai ners shall be airy and well  ventilated . 
3.2.1.2.6. 5 Availability of properly working thermometer and relative humidity devices  
3.2.1.2.7  Silkworm management and rearing  
3.2.1.2.7.1  General managemen t 
3.2.1.2.7.1.1  Enlarged area of silkworm bed shall be provided in correspondence with each stage of the 
silkworm development.  
3.2.1.2.7.1.2  Collect, exterminate, and dispose of abnormal, weak, scrubby, and diseased silkworm properly.  
3.2.1.2.7.1.3  Collect slower post -moulting or under grown silkworm than that of the same  development stage 
to rear separately.  
3.2.1.2.7.1.4  Availability of disposal measures for wastes e.g. silkworm excrete, mulberry branches and 
unconsumed leaves both inside and surrounding  
3.2.1.2.7.1.5  area of the rearing house.  
3.2.1.2.7.1.6  Adequate and  continuous feeding of mulberry leaves at each meal by keeping their freshness and 
maintaining unconsumed leaves at low level to facilitate air flow and prevent accumulation of heat and 
dampness that cause disease to silkworm  
3.2.1.2.7.1.7  Manage density o f silkworms not too crowded to prevent heat accumulation and insufficient 
feeding  
3.2.1.2.7.1.8  Prior to pre -moulting of silkworm, remove excreta and unconsumed leaves from rearing house 
and reduce moisture of such rearing house.  
3.2.1.2.7.1.9  After post -moulting of silkworm and before feeding of first meal of each development stage, there 
shall be prevention and disinfection from silkworm diseases . 
3.2.1.2.7.2  Rearing  of young larva  
3.2.1.2.7.2.1  Availability of clean material lining for rearing containers  
3.2.1.2.7.2.2  Properly prevent and disinfect the larvae from the disease that may be carried by the infected 
larvae.   
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 3.2.1.2.7.2.3  Collection of newly hatched larvae from egg sheets.  
3.2.1.2.7.2.4  Carefully transfer to avoid causing any harm to the larvae.  
3.2.1.2.7.2.5  Evenly spread of larvae for their healthy growth.  
3.2.1.2.8  Management of mature silkworms and cocoons  
3.2.1.2.8. 1 Silkworms laid down on mounting frame shall be mature.  
NOTE:  Maturity for silkworms is 55 days  
3.2.1.2.8.2  Quantity of silkworms shall b e proportional to the types and sizes of mounting frames to provide 
sufficient space for spinning with good air flow.  
3.2.1.2.8.3  Collect dead or non -spinning silkworms to exterminate and/or dispose properly.  
3.2.1.2.8.4  Harvest cocoons after larvae develo p to fully formed pupae and when their skins turn yellow 
brown.  
3.2.1.2.8.5  De-floss the outer part covering cocoon shells.  
3.2.1.2.8.6  Sort defect cocoons from the good ones.  
3.2.1.2.8.7  Keep cocoons waiting for transportation in a manner that they are not too densely overlaid 
causing accumulated heat and moisture that affect cocoon quality.  
3.2.1.2.8.8  Packing shall not damage cocoon.  
3.2.1.2.9  Transportation of cocoons  
Prevent damage of cocoons from accumulation of heat and moisture by good ventilation management.  
3.2.1.2.10  Hygiene and cleanness  
3.2.1.2.10.1  Availability of preventive measure for silkworm diseases that may be carried by persons 
entering the rearing house.  
3.2.1.2.10.2  Availability of cleaning and disinfecting measures for the surrounding area of r earing house.  
3.2.1.2.10.3  Availability of cleaning and disinfecting measures for transported vehicle for silkworm eggs and 
larvae.  
3.2.1.2.10.4  There shall be disposal measures for wastes e.g. silkworm excrete, mulberry branches and 
leaves after each rear ing cycle both inside and surrounding area of the rearing house to prevent the spread of 
diseases.  DRS 357: 2017  
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 3.2.1.2.10.5  In case of disease spreading in the rearing house, disinfection shall be carried out before 
moving tools, equipment, and remaining materials, in cluding silkworm excrete . 
3.2.1.2.11  Record keeping  
Record the following information:  
a) day-month -year of silkworm mounting ; 
b) daily temperature and relative humidity of silkworm rearing house ; 
c) keep records for at least 1 year ; 
d) day-month -year of harvesting fresh cocoon ; 
e) day-month -year of the first hatching  
f) application of substances used to prevent and control silkworm diseases ; and  
g) cleaning and disfecting the tools, equipment and materials used  
3.2.2  Minor re quirements  
3.2.2.1  Production inputs  
3.2.2.1.1  Silkworm eggs  
Known date (day/month/year)  of production  
3.2.2.1.2  Mulberry leaves  
3.2.2.1.2.1  The quantity of mulberry leaves shall be sufficient for feeding each lot of silkworms.  
3.2.2.1.2.2  Mulberry leaves should be fresh, clean, without damage from pests and diseases that affect 
the health of silkworms.   
3.2.2.2  Materials, tools and equipment  
Availability of clean, moisture preserved, and well ventilated covering materials used for young larva rearing 
tray or container  
3.2.2.3  Silkworm management and rearing  
3.2.2.3.1  General management  
Appropriate maturity of mulberry leaves should be suitable for each stage of the silkworm development in order 
to provide sufficient nutrients.   
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 3.2.2.3.2  Rearing of young larva  
3.2.2.3.2.1  Mulberry leaves for feeding shall be chopped to appropriate size and shape and spread evenly 
to help larva eat ing. 
3.2.2.3.2.2  Areas or shelves allocated for flat basket for newly hatched larvae shall be of temperature 
between 27 ºC and 28 ºC and relative humidity not lower than 90%.  
3.2.2.3.2.3  Areas or shelves allocated for flat basket for larvae of the second and  third instar larva shall be 
of temperature between 26 ºC and 28 ºC and relative humidity not lower than 80% except the times before pre -
moulting silkworm and during moulting . 
3.2.2.4  Management of mature silkworms and cocoons  
Place mounting frame of spinning silkwo rms in the area of relative humidity between 65% and 70%.  
3.2.2.5  Record keeping  
Record the following information regarding day -month -year of egg incubation (in case of farmer self -operation)  
3.2.3  Recommendations  
3.2.3.1  Production inputs  
3.2.3.1.1  Silkworm eggs  
3.2.3.1.1.1  Known source  of production  
3.2.3.1.1.2  Come from production source of not less than 90% hatching rate  
3.2.3.1.2  Third instar larva (in case that farmer does not rear the first and second instar larva)  
Come from the sources with good transport management, temperature not higher than 27 ºC, relative humidity 
between 75% and 85%. The transport should be done after moulting and feeding of the first meal. There should 
be preventive measures for pest in order to obtain the healthy third instar larva  
3.2.3.2  Materials, tools and equipment  
3.2.3.2.1 Availability of sieve for even dispersion of moisture absorbents and disinfectants  
3.2.3.2.2 Availability of scale for weighing mulberry leaves  DRS 357: 2017  
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 3.2.3.3  Silkworm management and rearing  
3.2.3.3.1  Hatching (in case of farmer self -operation)  
Control temperature to be maintained between 25 ºC and 26 ºC, relative humidity to be maintained between 80% 
and 85%, and manage light exposure in order to develop healthy embryo and to hatch concurrently on specified 
period of time.  
3.2.3.3.2  Rearing of Grown larva  
Areas or shelves allocated for flat basket for rearing shall be of temperature between 24 ºC and 25 ºC and relative 
humidity between 70% and 75% except the times before pre -moulting and during moulting, the relative humidity 
shall be reduced  
3.2.3.4  Management of mature silkworms and cocoons  
3.2.3.3.1  Place mounting frame of spinning silkworms in the area of temperature between 24 ๐C and 25 ๐C 
with good air flow.  
3.2.3.3 .2 Sort the infected cocoons from the other defectives to exterminate and/or dispose or utilise properly  
3.2.3.5  Record keeping  
Record the following information:  
a) date and time of pre -moulting and postmoulting  
b) description of abnormality of silkworm  
c) problems and obstacles of each lot of rearing  
4 Assessment  Criteria  
Assessment criteria for  compliance as detailed in clause 3 shall be as follows:  
a) All of the major requirements shall be fully complied with.  
b) The minor requirements shall be complied with not less than 60% of total number of minor  
c) requirements (the improvement up to 70% of all minor requirements shall be made within 2 years)  
   
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 Annex  A 
(informative)  
 
Illustration of silk cocoon  
 
Figure A.1  first to fifth instar lava of silk worm  
 
 
Figure A.2 Silkworm  
DRS 357: 2017  
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Figure A.3 Premoulting silkworms  
Illustrating the triangular shape at junction of head and thorax  
 
 
Figure A.4 Post moulting silk worms  
Illustrating bigger head and paler colour than those of pre -moulting with wrinkled skin and start eating  
 
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Figure A.5 Mature silkworm  
Illustrating transparent body with up -rising head and eagerly moving, ready for cocoon spinning  
 
Figure A.6 Double cocoon  
Double cocoon means a cocoon jointly built by at least two silkworms. Such cocoon, when reeling tends to 
break often because their silk baves intertwined with each other. The silk yarn is uneven and lower reeling 
efficiency. Double cocoon is caused by various reasons such as varieties, overcrowded silkworms per mounting 
frame, type of mounting frame is not proper for silk worms. Double cocoon is normally used as material for 
dupion  
(Dupion means silk reeled from defective cocoons. The yarn is large and suitable for warp for weaving)  
DRS 357: 2017  
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Figure A.7 Pierced cocoon  
Pierced cocoon means a cocoon pierced by Uzi fly maggot, or silkworm moth, or ants, or other animals, leaving 
a hole on the cocoon and causing silk yarn breaking and rather low reeling efficien cy 
 
Figure A.8 Inside soiled cocoon  
Inside soiled cocoon means a cocoon containing dead pupa or spinning by infected silkworm which dies inside 
either at larva or pupa stage, and causing stains. When reeling, will produce low quality silk yarn  
 
Figure A.9 outside soiled cocoon  
 
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 Outside soiled cocoon means cocoon stained by other silkworm excrete before cocooning or infected silkworm 
putrefied the cocoon, which makes it difficult to reel.  
 
Figure A.10 Thin -shelled cocoon  
Thin shelled cocoon means a cocoo n produced by ill -fed silkworm with poor spinning ability and cause thin 
shell. In other case, the mature silkworm is late in mounting, thus spinning on the side of rearing trays or corner 
of rearing table.  
 
Figure A.11 Loose -shelled cocoon  
Loose -shelled cocoon means a cocoon produced under an improper environmental condition. The cocoon is 
flossy and not compact. When reeled, the yarn often breaks.  
 
DRS 357: 2017  
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Figure A.12 Thin -ended cocoon  
Thin ended cocoon means a cocoon that due to the characteristic of some si lkworm varieties or caused by high 
temperature during egg incubation. Sometimes this occurs due to low temperature during cocooning. The 
cocoon is unusually thin at one end, and when boiled thinner part is soggy and broken and difficult to reel  
 
Figure A. 13 Malformed cocoon  
Malformed cocoon means a cocoon produced from silk worm in an inappropriate mounting frame, or from weak 
silkworm preventing the silkworms from completing the cocooning process and the cocoon shape becomes 
irregular. When boiled with no rmal cocoons, such cocoons are either soggy or harden depending on their 
characteristics.  
  
 
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Figure A.14 Printed cocoon  
Printed cocoon or cocoon with prints of mounting frame means a cocoon produced by a silkworm attached to 
the edge of mounting frame or  lining paper or improper mounting frame. The cocoon is too flat with some thicker 
parts due to overcrowded silkworms per mounting frame, leaving inadequate space for cocooning.  
 
Figure A.15 crushed cocoon  
Crushed cocoon means a cocoon caused by crushing to one another, over packing or inappropriate handling 
during transportation and storage.  
 
  
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Figure A.16 Mouldy cocoon  
Mouldy cocoon means a cocoon stored under poor ventilation causing moisture accumulation in the container 
or the storage room. This co ndition allows mould to grow on the cocoon shell.  
 
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 Bibliography  
[1] FAO Agricultural Services Bulletin 80. 1990. Sericulture Training Manual. FAO, Rome.  
[2] FAO Agricultural Services Bulletin 73/2. 1992. Silkworm Rearing. FAO, Rome.  
 DRS 357: 2017  
ICS 59.040  
 
©RSB 2017 All right s reserved