The silk glands of silkworms are modified labial glands that secrete silk thread. They are located below the alimentary canal and occupy most of the body cavity in the final instar. The glands have 3 regions - posterior, middle, and anterior. The posterior region contains folds that secrete fibroin proteins. The middle region stores and matures the fibroin. The anterior region is thin and guides the silk fibers through the spinneret opening. The 2 silk threads are called brims and bind together via secreted sericin layers to form the silk filament.

1. Course In-Charge
Mr.S.Srinivasnaik
Assistant Professor
Department of Entomology
LECTURE No.9
Sericulture- Brief history of sericulture in India, kinds of
silkworms, their systematic position, brief life cycle &
distribution, morphology and classification of mulberry
silkworm; silk glands
ENTO 332 (1+1):Management of Beneficial Insects

2. SILK GLANDS

3. The silk thread of the cocoon is secreted by a pair of
glands which are actually modified labial glands.
These glands are well differentiated in the 4th and
5th instar.
They lie below the alimentary canal.
They are large when fully grown and in final instar
they occupies most of the body cavity ventral to the
alimentary canal and accounts for 50 per cent of the
body weight.
The silk glands are tubular in nature and the width
of the tube varies in different regions of the glands.
The entire gland is formed by 3-layers
1) The outer tunica propria of uniform thickness
2) Middle grandular layer
3) Inner tunica intima

4.  The inner tunica intima is very thick in the anterior region
and it is shed at each moult.
 There are 3 distinct regions in the silk gland differing in
the structure and function. They are posterior region,
middle region and anterior region.
 The posterior most region is highly folded and the folds lie
in the mid of the dermo visceral muscle.
 They secrete major proteins of the silk viz., fibroin.
 The middle region is the most prominent region and is
also widest it is folded into ‘W’ shape structure and the
middle region acts as a reservoir of the fibroin secreted by
the posterior region.
 The fibroin matures in this region during the storage
period. The layer of the sericin secreted by posterior
limbs of the middle region is called Sericin- 1 that added
around the sericin-1 by the middle limb with the sericin-2
and that added around the sericin-2 by the anterior is the
sericin-3.

5. • The anterior region is of uniform thickness and is
very thin and does not secrete any material.
• It serves only to conduct the silk fibre assembles
in the middle region.
• The two sides are open at the base of the
median projection in the labium called Spinneret
which draws out silk in the form of fine filament.
• The silk is moulded as a thread as it passes
through silk press which resembles a typical
salivary pump.
• The threads of the two sides are called brims
and the sericin layer bind them together into a
single filament or bave.

11. https://youtu.be/A8Gs27xqIxo
DISSECTION OF SILK GLANDS

12. REFERENCES:
•Abrol, D.P.2010. Bees and Bee keeping in India. Kalyani Publishers, Ludhiana. Pp450
•David, B.V and Kumara Swami, T. 2016. Elements of Economic Entomology, Popular Book
Depot, Madras. Pp536
•Ganga, G and Sulochana Chetty, J. 2008. An introduction to sericulture. Oxford and IBH
Publishing Co.Pvt.Ltd., New Delhi. Pp160
•Gautam, R.D.2008. Biological Pest Suppression
•Ghorai, N. 1995. Lac culture in India. International Books & Periodicals Supply Service.
•Jolly, M.S. 1987. Appropriate sericulture techniques . International center for training and
research in tropical sericulture, Mysore. Pp209
•Krishnaswami, S., Narasimma, M.N., Suryanarayan, S.K and Kumararaj,S. 1995. Silkworm
Rearing. Sericulture Manual 2. Oxford and IBH Publishing Co.Pvt.Ltd., New Delhi. Pp150
•Mishra, R.C.1995. Honeybees and their management in India. ICAR, New Delhi.
•Patnaik, R.K.2008. Mulberry Cultivation
•Rangaswami, G., Narasimhanna, M.N., Kasiviswanatham, K., Sastry, C.R and Jolly, M.S. 1995.
Mulberry Cultivation. Sericulture Manual 2. Oxford and IBH Publishing Co.Pvt.Ltd.,New Delhi.
Pp150
•Sailesh Chattopadhyay. 2011. Introduction to lac and lac culture. Tech. Bulletin.FBTI:01/2011
•Abrol, D.P.2010. Bees and Bee keeping in India. Kalyani Publishers, Ludhiana. Pp450
•David, B.V and Kumara Swami, T. 2016. Elements of Economic Entomology, Popular Book
Depot, Madras. Pp536
•Ganga, G and Sulochana Chetty, J. 2008. An introduction to sericulture. Oxford and IBH
Publishing Co.Pvt.Ltd., New Delhi. Pp160
•Gautam, R.D.2008. Biological Pest Suppression

13. MARKS ALLOTMENT
1. Mid semester Examination : 50M
2. Final Practical Examination : 25M
3. Class Work : 25M
Record: 10M
Observation Notes: 5M
Attendance: 3M
Discipline and attentive and answering: 2M
Internal Tests: 5M
4. Assignment : 25M
Power Point Presentation:10M
Model preparation:5M
Photo frame/Laminations :5M
Internal Write ups:5M

14. “Strive hard to make farming profitable and sustainable for the prosperous Nation”