There are different races of Bombyx mori (silkworm) based on their voltinism (number of generations per year) and moulting. Races can be univoltine (1 generation/year), bivoltine (2 generations/year), or multivoltine (more than 2 generations/year). They also differ based on whether their eggs are diapausing (dormant) or non-diapausing. Bivoltine races lay both types of eggs, while univoltine races only lay diapausing eggs and multivoltine only lay non-diapausing eggs. Races also vary in their larval stage duration, cocoon characteristics,

1. Races of
Bombyx mori
Based on voltinism &
moultinism

2. RACES:
A population within a species that is distinct in some way,
especially a subspecies.
Indigenous- originating in and characteristic of a particular
region or country; native.
Eg., Pure Mysore, Nistari.
Exotic- plant or animal species introduced into an area
where they do not occur naturally, non-native species.
Eg., E16, Daizo etc.,

3. Classification of Bombyx mori
Classification based on:
•Distribution
•Moulting
•Voltinism
•Cocoon color
•Rearing period
•Larval markings

4. Voltinism
It is the ability of many insect groups to produce from one
to several generations a year.
•Species producing one generation a year -univoltine
•Species producing two generations -bivoltine
•Species producing several generations -multivoltine

5. Voltinism in Bombyx mori

6. Univoltine races:
• produce ONE generation per year.
• larval weight is comparatively higher and
cocoons are heavy.
• Denier of the silk filament is above 2.3.
• not suitable for summer & winter rearings,
since the larvae are weak against
unfavourable conditions.
• They lay only diapausing eggs.
• All European races are univoltines eg.,E16

7. Bivoltine races:
• produce TWO generations per year.
• length of the larval stage is short.
• The leaf consumption to cocoon production
is less, and the quality of the cocoons inferior
to that of Univoltine races.
• cocoon weight, shell weight, silk % &
filament length lesser than uni/mono
voltines.
• Most of the temperate races are bivoltines
• Lay both non hibernating and non
hibernating eggs
• eg.,NB4D2, NB18, KA, NB7 etc

8. Multivoltine races:
• produce more than 5-6 generations per year.
• length of the larval duration is short.
• In most of the polyvoltine races the leaf
cocoon ratio is high
• the length of the filament is short
• cocoon filament is fine and clean with
little lousiness; but with more lustrous.
• the larvae are robust and can tolerate
fluctuating environmental conditions and
hence best suited for tropical climates
• they lay only non diapausing eggs.
• eg.,pure mysore, c.nichi, hosa mysore.

10. How do they differ?
Diapausing eggs
• Also called as “Kuradone eggs”.
• Eggs remain in dormant stage
• It is produced by the 2nd generations of
univoltine silkworms & 3rd generations
of bivoltine silkworms.
• Eggs are dark brown before entering
to diapause stage
• Diapause can be broken by some
treatments such as acid treatment.
Non diapausing eggs
• Also called as “Nomadane eggs”.
• Eggs are not dormant.
• It is produced by the multivoltine
silkworms
• No color change, but turns bluish
black before hatching.
• No treatment required

11. How do they differ?
Bivoltine race
• Eggs may be diapausing or non
diapausing
• Loose egg production is mostly done
• Relatively poor disease resistant
• Cannot tolerate beyond 28⁰C
• Completes lifecycle in _______ days
• Eggs can be preserved upto 6-10
months
• 1500-1700 eggs/ gram
• Shell ratio of 20-25
• Filament length 1000-2600m/ cocoon
Multivoltine race
• Non diapausing eggs are produced
• Flat card sheet method is done
• Relatively disease resistant
• Can tolerate beyond 28⁰C
• Completes the lifecycle in 26-27 days.
• Eggs cant be stored for more than 20
days
• 1800-2100 eggs/gram
• Shell ratio of 12-14
• Filament length 400-500m/ cocoon

12. Moultinism
It is the classification based on number of moultings
throughout the lifecycle.
Silkworms can be classified into:
•tri moulters
•tetra moulters
•penta moulters
•hexa moulters (very rare)

13. Trimoulters:
• They moult three times during larval period.
• The larval growth is limited
• Short larval duration ranging from 15-18 days.
• Pupae & moths are small.
• Cocoon weight is less, cocoon filament is fine & denier of the silk filament ranges
from 1.6 to 1.7.

14. Tetramoulters:
• They moult four times during their larval stage.
• Medium the larval stage ranging from 23-28 days.
• Medium larval growth and cocoon weight.
• Denier is 2-2.5.
• Tetra moulters are cosmopolitan in their distribution.
• Most of the commercial silkworms belong to this group.

15. Pentamoulters:
• They moult five times during their larval stage.
• The length of the larval stage is long
• Larval weight is high and cocoons are heavy, filament length is more.
• Denier of the silk filament is very high.