Life cycle of Honeybee and Silkworm and their economic importance

1. SOME INVERTEBRATES
Silkworm and Honeybee
Study of Insects = Entomology

2. Silkworm
• The art of rearing silkworm for commercial benefit is called Sericulture
• Silkworm produces silk thread which is used to make silk cloth.
• It is the caterpillar of a moth whose cocoon is used to make silk.
• Silk is obtained from larvae of silkworm so it is called silkworm.
• It is believed that the origin of silkworm was from China.

3. Silkworm in Nepal
• In Nepal, two families of silkworm are being reared:
• Bombycidae : Seri-silkworm (Bombyx mori)
• Saturnididae : Eri-silkworm ( Attacus ricini)
• Bombyx mori produces mulberry silk and feeds on
mulberry leaves.
• Also k/a mulberry silkworm or seri-silkworm.
• Silk produced is white or light yellow and of good
quality.
• Attacus ricini feeds on castor leaves and yields
creamy white silk.

4. External Structure
• The adult moths are 25 mm in length and the span of wings
is 40-50 mm.
• The female silkworm moths are larger than the males.
• Usually whitish in color and in some forms specially the
males have grey marks on their wings.
• The body is distinctly divisible into three segments—head,
thorax and abdomen.
• The head contains distinct eyes and feathery antennae, the
latter being larger in males.
• Three pairs of legs and two pairs of wings are present in the
thoracic region. Abdomen is hairy and wider.
• Female moths do not have any mouth. They rarely move.
• The entire body is covered by minute scales.

6. Egg
• Egg is the first stage of a silkworm’s life cycle.
• The female moth lays an egg about the size of an ink
dot during summer or the early fall.
• The warmth of the spring stimulates the egg to hatch.
• Female lays about 300 - 400 eggs on mulberry leaves
• Eggs stick to leaves with gelatinous secretion
• Creamy yellow first, after few days they change into
gray
• In about18°C to 25°C larva hatches within 10 to 12
days.
• Egg laying is completed in 1-24 hours.

7. Larva/Caterpillar
• The larva is the vegetative stage where growth takes
place.
• After hatching the larva is extremely hairy.
• It feeds on mulberry leaves and grow very quickly.
• After four to five days it becomes inactive.
• Goes through five growth stages called ‘Instars’.
• First instar molts. Such molting occurs four times
• The enzyme secreted by the salivary gland comes on
contact with air and becomes a hard and fine thread
which is known as silk which later becomes cocoon.
• The larval stage lasts about 27 days

9. Pupa
• It is inactive stage and doesn’t take food.
• The silk cocoon serves as protection for the pupa and
growth takes place inside the cocoon.
• Cocoons are shades of white, cream and yellow
depending on silkworm genetics.
• After a final molt inside the cocoon, the larva develops
into the brown, chitin covered structure called the
pupa.
• If the silkworms are allowed to mature and break
through the cocoon, the silk would be rendered useless
for commercial purposes.
• The end of the silk is then located and the cocoon
unwound onto a spindle to be made into thread.

10. Pupa (Cocoon)
• Cocoon is the stage in which the larva spins silk threads
around it, to protect itself from its predators.
• The color of the cocoon varies, depending upon what the
silkworm eats.
• It can range from white to golden yellow.
• The second molting occurs inside the cocoon, when the
larva turns into a brown pupa.
• It takes about 2-3 weeks for the pupa to metamorphose
into an adult moth.
• For obtaining silk, the cocoon are treated with hot water or
placed in hot oven to kill the pupa inside. The silk is
unwounded from the cocoons and twisted into the ground.
• A single cocoon gives about 1000 feet of unbroken silk
• 454 gm silk is obtained from 25,000 cocoons.

11. Adult/Imago
• The adult stage completes the life cycle of Bombyx
mori.
• It is the reproductive stage where adults mate and
females lay eggs.
• Moths are flightless and lack functional mouth parts,
so are unable to consume the food/nutrition.
• Once the adult moth comes out of its cocoon, its only
purpose is to find a member of the opposite sex, and
mate.
• Males are larger than females and more active.
• They flap their wings rapidly to attract the females.
• Within 24 hours of mating, the male moth dies, while
the female lays abundant eggs

12. Life cycle

13. Economic importance
• Silkworms are useful because they produce
high quality silk fiber which is used to weave
clothes, shawls, sari, tie and expensive
clothing.
• Similarly, silk is used to prepare parachute,
special type of tyre for cars, the outer covering
of telephone wires.

14. Characteristics of Silk
• Silk is natural fiber. It is also called queen of fiber
because it is soft shiny, strong and durable as
compared to other artificial fiber.
• Silk has a smooth, soft texture that is not slippery,
unlike many synthetic fibers.
• Silk is one of the strongest natural fibers, but it
loses up to 20% of its strength when wet.
• It has a good moisture regain of 11%. Absorbs
water easily and dries easily.
• Its elasticity is moderate to poor: if elongated
even a small amount, it remains stretched

15. Introduction:
 Apiculture (Bee keeping) is the maintenance of honey bee colonies, by
humans in order to collect products like honey, beeswax, propolisetc.
 A location where bee colonies are kept is called an apiary or "beeyard’’.
 In Nepal, Apis mellifera and Apis cerena are honey producing bees in
Nepal.
 Honey bees are highly organized social insects and their
systematic position is as follows –

16. Anatomy

17.  Species of Honey bees:
1. Apis dorsata (The rock- bee)
 This is the largest honeybee.
 Builds single large open comb on high
branches of trees and rocks.
 Produces large quantity of honey, but this
bee is difficult to domesticate.
2. Apis cerana (The Indian bee)
 Medium – sized.
 Hive consists of several parallel combs in
cavities of tree trunks, earthen pots, etc.
 This bee is not so ferocious and can be
domesticated.
 Found at altitude of 60-3500 m and
produces twice a year.

18. 3. Apis florea (The little bee)
 Small – sized.
 Builds single small combs in bushes,
hedges, etc.
 Honey yield is poor.
4. Apis mellifera (The European bee)
 Somewhat look likes the Indian bee
(Apis indica).
 This has been introduced in many
parts of the world including Nepal.
 It is easily domesticated.

19. The Bee colony
A honey bee colony has
three castes –Queen, worker
and drone.
Queen: Fertile female
• Queen bee is the only fertile female in colony
• She is largest in size.
• No wax glands.
• Live for about 3 - 4 years.
• May lay eggs at the rate of 1500-2000 perday

20. Drones: Fertile male
• Drones are the male member of colony.
• Larger than workers but smaller than queen.
• Drones can live up to about 60 days.
• Sting and wax gland absent.
• Develops from unfertilized egg.
• The sole duty of drone is to fertilized the virginqueen.
Worker: Sterile female and smallest
•Have well-developed sting and Hind legs have “pollen basket”
for collecting pollen.
 They perform different duties depending upon their age which
are as follows:
 Day 1-14: Activity inside the hive such as cleaning the hive,
feeding the larvae, etc.
 Day 14-20 :Guard the entrance of the hive
 Day 21- 35: Foraging, i.e. collecting the nectar and pollen
from the surrounding.

22. Life cycle
• The lifecycle of a honey bee consists of four main
stages: Egg, Larva, Pupa, and Adult.
• Within a normal hive situation, a single queen
bee lays fertilized and unfertilized eggs.
• Fertilized eggs can hatch worker and queen bees,
unfertilized eggs hatch drone bees.
• Eggs hatch after about 3 days, but development
rates and processes vary among bees within the
hive, as well as between species in the genus.

23. Egg
• An egg is laid by the honey bee queen in a wax,
hexagonal egg cell. The egg is about the size of a
grain of rice and initially stands upright in the cell,
but falls onto its side by the third day. The honey
bee queen may lay between to 2000 and 3000
eggs per day.
• Fertilized eggs will become females (workers or
potential queens). Unfertilized eggs will become
drones (male honey bees) and are laid in 'drone
cells' which are larger cells than those of worker
bees.
• A potential future queen honey bee is laid in a
special cell, called a 'queen cell'

24. Development of castes

25. Larva
• After 3 days, the egg develops into a larva, which looks like
a small white grub. It has no legs and is blind.
• The larvae are fed by young worker bees that have not yet
left the hive or nest. Initially, all the larvae are fed royal
jelly for three days, and after this they are fed bee bread,
which is a mixture of honey and pollen.
• A larva destined to be a queen is fed only on royal jelly,
which is a special substance made in special glands in the
head, and the salivary glands in the mouth. Royal jelly is
sometimes called 'bee milk' and is produced by young
nurse bees (worker bees of between 5 and 14 days
old). Royal jelly contains protein, vitamins, fats (lipids), and
sugar.
• As the larva grows, it will moult (shed its outer skin) several
times. After about 6 days (depending on whether the bee
is a worker, drone or queen), the egg cell is covered with a
layer of wax by the worker bees.

26. Pupa
• Inside the sealed egg cell, the larva begins to spin a cocoon around
itself and pupate. During this phase, the larva develops into a
recognizable bee, with wings, legs, head, thorax and abdomen.
Adult
• Eventually, a young adult bee will emerge from the egg cell, by
chewing its way through the wax capping.
• All in all, from the time the egg was laid, it takes new queens about
16 days to emerge from the egg cell, whereas workers require
between 18 and 22 days to fully develop, and drones need 24 days
• As soon as new queen comes out, the old queen leaves the hives
with workers. This is called primary swarming. Then the queen
takes nuptial flight (It is the flight in which virgin queen mates
with the drone males) and the process continues.

27. Metamorphosis

31. Economic importance
• It is involved with the collection valuable products such as honey ,
wax , royal jelly etc.
• Provides honey which is the most valuable nutritional food.
• Provides bee wax which is used in many industries, including
cosmetics industries, polishing industries, pharmaceutical
industries, etc.
• Plays an excellent role in pollination. Honey bees are the best
pollinating agents which help in increasing the yield of several
crops. It is responsible for the one- third population of the world
food by the pollination
• According to the recent studies, the honey bee’s venom contains a
mixture of proteins which can potentially be used as a prophylactic
to destroying the HIV virus that causes AIDS in humans.
• If bees disappeared from the earth, Human beings would have only
four years to survive.