Life Cycle of Mosquito

Life Cycle of Mosquito

Published by: Nuru

Published date: 17 Jan 2022

Life Cycle of Mosquito in Grade 9 Science, Reference Notes

Mosquito

There are various kinds of animals in the earth. They are divided into vertebrates and invertebrates. In this topic, we study about invertebrates (Mosquito). Mosquitoes are found all over the world but they are mostly common in humid and temperate climate. There are 2,700 species of mosquito in Nepal.Carbon dioxide gives mosquitoes the signal that blood is nearby, and since we exhale CO2, we make it easy for mosquitoes to find us.

Classification of Mosquito are as follows:

Kingdom: Animalia
Sub kingdom: Invertebrata
Phylum: Arthopoda
Class: Insecta
Common name: Mosquito

Culex tarsalis and Anopheles freeborni are two main mosquitoes found in Nepal.

Structure of the mosquito:

The body of mosquito is divided into three parts: head, thorax and abdomen.

Head: 

The head of the mosquito is very small and almost spherical in shape which is joined to thorax by the means of a short and narrow segment. The head bears a pair of compound eyes called palps and proboscis. There are 13 segments in each antenna. The second segment of each antenna possesses hearing organs called Johnston’s organs.

Thorax:

The thorax consists of three parts: Prothorax, Mesothorax and Metathorax.

Abdomen: 

The abdomen of a mosquito is made of nine segments. The abdomen possesses an anal opening and a genital opening. The ninth segment of a male mosquito bears an anal which helps in copulation.

Difference between male and female mosquitoes are as follows:

Male Female
Male mosquitoes only feed on sap of plant. Female mosquitoes bite and suck blood.
Antenna is provided with long hairs. Antenna is provided with short hairs.
Mouthparts are adapted for sucking. Mouthparts are adapted for sucking and biting.
Abdomen is smaller. Abdomen is larger.

Life Cycle of Mosquito are as follows:

  1. Egg
  2. Larva
  3. Pupa, and
  4. Adult

Egg

A mosquito lays egg usually in lakes, ponds, fields, puddles and in stagnant water. An anopheles mosquito lays 40 to 400 eggs at a time. Those eggs remain floated in water singly without being stuck to one another. On the other hand, a culex mosquito lays 300 eggs at a same time. Those eggs remain floated on water remaining attached together forming a shape of a boat.

Larva

Under favorable condition, eggs hatch out larva within 2 to 3 days. They are seen transparent and live on algae. At this stage, they are voracious. A larva has broad thorax with three segments joined together. The abdomen is also segmented. The head has a pair of compound eyes. The bristles are found on thorax and abdomen too. On the last segment of the abdomen, there are four gills and a respiratory siphon. Larva remains suspended near the surface of the water. An anopheles larva lies parallel to water surface whereas a culex larva lies making an angle with water surface.

Pupa

The larva develops into pupa within a week if it gets suitable temperature and sufficient food. This is in fact, a resting stage in many insects but a mosquito pupa is also very active.  It swims a lot and breathes through siphon. However, it does not eat any food. The duration of pupal stage is 2 to 7 stage. The head and thorax of a pupa are fused together called cephalothorax. The abdomen is curved.

Adult

A fully developed mosquito emerges out of the pupal case and flies away. The female one begins to lay eggs after it mates with the male one at maturity.

Differences between Culex and Anopheles are as follows:

1. In terms of egg:

Culex Anopheles
Eggs are vertically laid in clusters on the surface of the water. Eggs are laid singly and horizontally on the surface of the water.
Eggs are cigar shaped. Eggs are boat shaped.
Eggs of culex mosquito are not provided with lateral air floats. Each egg has two lateral air floats, which help them in floatation.
Eggs are laid on dirty water. Eggs are laid on clean water.

2. In terms of Larva:

Culex Anopheles
Larva of culex mosquito is bottom feeder. Larva of anopheles mosquito is surface feeder.
The respiratory siphon is long. The respiratory siphon is short.
It forms an angle inside water. It remains parallel with water surface.

3. In terms of Pupa:

Culex Anopheles
The pupa is colourless. The pupa is green.
The respiratory trumpets are long and narrow. The respiratory trumpets are short and wide.
The abdomen is less bent. The abdomen is more bent.

4. In terms of adult:

Culex Anopheles
Body is provided with stouter legs. Body is provided with delicate legs.
Wings are transparent and can fly for long distance. Wings are spotted and cannot fly for long distance.
There is presence of small palpi near proboscis. The proboscis and palpi have same length.
At rest body lies parallel to the surface. At rest body is inclined at an angle of 45 ͦ to the surface.
It transmits filarial parasite. It transmits malarial parasite.

 

Some important terms:

Moulting:

The periodic shedding of the outer layer of the skin of larvae of insects to allow further growth is called Moulting.

Histogenesis:

Differentiation of tissues inside the puparium of insects is called Histogenesis.

Metamorphosis:

Period of rapid transformation from larval to adult stage is called metamorphosis.