Invertebrates Class 10 | SEE Biology Notes

Useful Insects/ Invertebrates:-

• Silkworm
• Honeybee, etc.

Honeybee: It is a social insect because it has a division of labor. The queen workers and drones have distinct roles in honey-comb.

Apiculture: The cultivation of honey bees.

Sericulture: The cultivation of silkworm.

Life cycle: Completed in four stages:- 

Puparium: The outer coat of pupa is called Puparium.

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Classification of silkworm and Honey bee:-

Body is divided into three distinct parts:-

• Head:- Compound eyes, a pair of antenna, and the mouthparts.
• Thorax:- It contains three pairs of jointed legs.
• Abdomen:- The abdomen is segmented.

Metamorphosis:- The metamorphosis is the important events in the life cycle of insects. The change from eggs to adults is the result of metamorphosis.

Silkworm/ Silkmoth:

• Its body is white creamy and 15mm long.
• Eggs:- a) Female lays 300 to 400 eggs at a time on the mulberry leaves.
  b) At temperature 18°c to 25°c, eggs are hatched into larva after 10-20 days.
• Larva:- a) It lives on mulberry leaves and it changes its skin four times that is called molting.
  b) It wraps skill thread to its body and converted into the cocoon.
  c) The silkworm needs one month to complete larva stages, etc.
• Pupa:- a) It is an inactive stage of life cycle. This stage is completed in 12 to 14 days.
  b) The cover of the pupa is called puparium. The pupa stage is also called Cocoon stage.
  c) The cocoon is the pupa stage and it is an inactive stage. The silk is obtained from a single cocoon. We put a cocoon in warm water to kill larva present inside of a cocoon.
  d) Diagram:-
  
  
• Advantage:-
  a) Its thread is used to produce costly clothes.
  b) It is used in surgery to sticking cut.
  c) Improve the economic condition of the farmer.
  d) It is used in phishing, etc.
• Features of silk thread:-
  a) The thread is proteinous, light, and strong.
  b) It has a special shining.
  c) It can be colored easily.
  d) It absorbs water readily.
  e) Silk clothes are suitable for all seasons, etc.

Honeybee:-

• Development of Honeybee:-
  

  Honeybee	Eggs	Larva	Pupa	Total days
  Queen	3	5*1/2	7*1/2	16
  Workers	3	6	12	21
  Drones	3	6	14*1/2	23*1/2

• Work division:-
  

  Bee and age	Function
  Drone	It makes hive warm and copulates with the queen.
  Queen	The queen is responsible for laying eggs and managing the hive. It produces different types of smell for hive management.
  Worker (1-3 days)	In this stage, these bees are called baby-bees. They are very weak, so they start to walk, attack with the hive, provide warmth to eggs, larva, and pupa. They eat surrounding foods and clean beehives.
  4-6 days	They feed honey and bee bread to developing larva and they eat themselves too.
  7-10 days	Head glands developed and produce Royal jelly. Young larva and Queen bee feed on Royal Jelly and they eat themselves too.
  12-17 days	a)Head gland become dry. b) Four pairs of wax glands are produced in the abdomen to produce wax. c) Wax is used to the male hive.
  18-20 days	a) Wax gland become dry. b) Poison glands are developed to protect the hive.
  21 days	They start to emerge from the hive for the collection of nectar and water.

• Mating flight/ Nuptial fight:- The mating of the queen with the drone in the air is called mating/ nuptial flight in which eggs are fertilized. After fertilizing eggs, drones die.
• Drone cell:- The queen lays eggs in drone cells for new drones.
• Worker cell:- The queen lays eggs in worker cell for future workers.
• Queen cell:- The egg laid in queen cell is developed in queen.
• Chromosome:- In honey bee, there is a 32 (16 pair) chromosome. The chromosome some carries genetic material from generation to generation.
• Royal jelly:- A substance secreted by bees to aid in the development of immature or young bees supplied in an extra meal to those that will become queen bee. It is secreted by Hypohyrax of nurses bee.
• Bee-bread:- A mixture of nectar and pollen made by workers bee and used as food for larva.

Answer these questions:

a) What is sericulture? What kind of silkworms are reared in Nepal?

Ans: The cultivation of silkworm is called sericulture. There are two types of silkworm reared in Nepal i.e Eri-silkworm and Seri-silkworm, etc.

b) Describe the structure of a silkworm with a diagram.

Ans:

Silkworm is midsized insect-like butterfly having white creamy color and 2-3 cm length. Its body is divided into three parts:- Head, thorax, and abdomen. It has a pair of antenna, wings and three pairs of legs.

c) In which phase does the silkworm produce silk fibers?

Ans: In the pupa stage the silkworm produces silk fibers.

d) How are eggs kept in the safe way when mulberry leaves are not available?

Ans: When mulberry leaves are not available then eggs can be store to keep in safe.

e) What is an instar? How many times does a silkworm molt in its larval stage?

Ans: The hatched larva is called the first instar. Five times silkworm molt in its larval stage.

f) What is Cocoon? Why is it kept in hot water or air to obtain silk fibers?

Ans: The pupa stage is called cocoon. It is kept in to obtain silk fibers because to kill pupa.

g) Explain the economic importance of silkworm.

Ans: Following are the economic importance of silkworm:
i) Silk is the use to make clothes.
ii) It improves the economic condition of farmers.
iii) Intestines of silkworms are extracted to make strings are extracted to make strings (gut), etc.

h) Mention the features of silk fibers.

Ans: Following are the features of silk fibers:-
i) Silk is a shining, light and durable fiber.
ii) It is longer and more elastic.
iii) It can be colored easily, etc.

i) Draw the life cycle of the silkworm.

Ans: 

j) How do eggs of silkworm get stuck with leaves?

Ans: Egga of silkworm get stuck with leaves due to that they are covered by gelatinous secretion.

k) Mention the systematic position of the silkworm.

Ans: Following are the systematic position of silkworm:
Kingdom: Animalia
Sub-kingdom: Invertebrata
Phylum: Arthropoda
Class: Insecta
Type: Silkworm