- Mosquitoes are two-winged flying insects that suck blood from humans and other animals.
- They are found all over the world but are mostly common in humid and temperate climate.
- They are generally found in the dark places such as bushes, holes in the trunk of the trees, corners of the room, bookcase, near ponds and ditches.
- Nowadays they are also found at the higher altitudes than the mild hilly regions due to climate change.
- They are carriers of a number of diseases, mostly in the tropics, causing illness and death on a large scale.
- They are nocturnal in feeding habit but in day time biting also occurs.
- Some species prefer biting at certain hours, at dusk and dawn or in the middle of the night.
- Female generally feeds on blood of humans and animals and male feeds on fruits and flower juices.
- For that reason female mosquitoes are only responsible for causing diseases not the male.
- Female mosquito has piercing and sucking type of mouth parts while male has only sucking type of the mouthparts.
- They can fly a long distance in a single day, about 20-30 km in a night and about 2 to 3 hours continuously without rest.
- Culex tarsalis and Anopheles freeborni are the two main types of mosquitoes which are common in Nepal.
- They have a small, soft, slender body, long jointed legs, needle shaped piercing and sucking mouth parts and body covered with minute scales.
- It measures about 3-4mm in length and the body is grayish-black in colour.
- The body is divided into three regions: head, thorax and abdomen.
- The head of the mosquito is very small and almost spherical which is connected to the thorax by means of short and narrow segment or neck.
- It bears a pair of kidney shaped compound eyes, a pair of antennae and the mouth parts called the palps and the proboscis.
- The eyes are comparatively big in proportion to the head.
- Each of the antennae is made up of 13 segments with whorls of hairs.
- The second segment of each antenna possesses the hearing organs called Johnston’s organs.
- Male has long hairs as compared to female on their antenna.
- The thorax consists of three regions: very small prothorax, large mesothorax and small metathorax.
- Each segments of thorax consists of a pair of long jointed legs and mesothorax consists of a pair of wings with halters or balancers.
- The wings are larger in the female than in the male.
- The vibration of wings results in buzzing sound.
- The abdomen is slender and made up of 9 segments.
- An anal opening and a genital opening is present in abdomen.
- The 9th segment of male bears an anal style that helps in copulation.
- Mosquitoes have four distinct phases in their life cycle: egg, larvae, pupae and an adult.
- They show complete metamorphosis in their life-cycle as they have all phases.
- The two sexes copulate during flight in the evening where the male gets attracted to the female by her high-pitched whine.
- The female usually mates only once but produces eggs at intervals throughout their life.
- In order to be able to do so, female requires blood meal.
- A female mosquito lay about 30-300 eggs depending upon the species at a time.
- The female anopheles lay about 30-100 eggs at a time which are laid separately and horizontally on the surface of water.
- The eggs are spindle shaped having lateral air floats.
- Similarly, a Culex lays about 200-300 eggs at a time which are glued together to form a small floating raft.
- The eggs of Culex are cigar-shapede. their upper end is narrow and pointed while the other end is broad and rounded.
- The eggs are hatched into larvae within 2-3 days under suitable condition.
- These are transparent and emerge from the lower end of each egg.
- They show caterpillar-like movement so they are also called wrigller.
- The body of larva is divided into head, thorax and abdomen.
- The head bears of a pair of compound eyes and mouthparts.
- The front part of the mouth possesses feeding brushes which help to feed.
- The thorax is broad, un-segmented and has no appendages.
- On the lateral sides, three pairs of tufts of hairs are present.
- The abdomen is made up of nine segments each of which bears bristles.
- The dorsal side of eighth segment possesses a siphon which bears a pair of
- Spiracles help in respiration.
- Tracheal gills are present in ninth segment around the anus.
- This stage lasts for about 2 weeks during which it moults three to four times enlarging its size with each moulting.
- The larva of culex at rest hangs at an angle from the surface of water whereas the larva of an anopheles lies parallel to the surface of water.
- The fully grown larva lives in water and develops into pupa.
larvae of Culex larvae of Anopheles
- Commonly known as tumbler.
- Body is comma shaped and can be divided into anterior swollen part called cephalothorax and the posterior elongated hook-like abdomen.
- The pupa is enclosed in transparent membrane called puparium.
- Pupa of mosquito is very active as compared to other insects.
- It always swims with the help of its paddle.
- Mouthparts are absent so it does not feed on anything.
- It respires with the help of respiratory trumpets.
- It lasts for about 2-7 days during which the adult organs are developed.
pupa of Culex pupa of Anopheles
- The pupal stage lasts for short duration.
- The pupa develops the body organs inside it after the completion of the metamorphosis.
- Thus, a perfect adult insect, an imago is formed.
- The mosquito is completely young in this stage which emerges when the pupal skin splits.
- The wings get dried by vibrating after which the mosquito flies in air within 5-10 minutes.
- The male and female mates and the female gets ready to lay eggs again.
- In this way the life cycle of mosquito continues.
adult Culex adult Anopheles