Mosquitoes are annoying, swarming, hitting pests, and some are carriers of malaria, yellow fever, dengue fever, filariasis, and encephalomyelitis. Mosquitoes can be distinguished from other Diptera by their fragile, small appearance. Females have elongated mouth parts and a distinct proboscis well suited for piercing and sucking blood. Scales are present along the wing veins and along the lower wing margins.
The sexes can be distinguished by the antennae: in females they are long and slender with a few short hairs; in the male they are feathery and plumose. Close examination shows the antennae to be composed of 14 to 15 segments. The venation of the wings is also characteristic for mosquitoes and is helpful in species identification. Mosquitoes are particularly attracted to man and animals, especially to bright light and dark-colored clothing. The females are the blood suckers and cannot produce fertile eggs without ingesting blood. It is postulated that the blood supplies the serotonin and epinephrine necessary for production of gonadotropic hormone by the mosquito, required for ovulation. The eggs are laid on the surface of water and hatch into aquatic "wiggletails". These subsequently metamorphose into adults. Three genera-Anopheles, Aedes, Culex-transmit disease to man.
Mosquito control
1. Mechanical methods
Wire screens for windows and doors. Mosquito nets. Repellants; certain lotions or creams applied to the skin repel mosquitoes from bitting eg, citrignella oil, Indalone. Animal barrier: Placing farm animals between the breeding places and human habitations would deviate mosquitoes (particularly zoophilic) from biting man.
2. Natural or physical methods (ecological interference)
Changing the environment so as to become unsuitable for the mosquitoe eg, filling or drainage of the breeding place. Developing of hade if larvae require sunshine and vice versa. Changing of water level, water current, PH.
3. Biological methods
Introduction of a natural enemy (predator): a fish (Gambusia affinis) feed on larvae and pupae; release of sterilized males (X-ray or chemical agents) which compete with males in nature, mating with females. and resulting in reduction of the forth coming generation.
4. Chemical methods (insecticides)
Used the ones against adults (adulticides). Insecticides act on contact being absorbed through the cuticle (contact poison). These are applied as space spray with an insecticide, which causes immediate knockdown of mosquitoes eg. pyrethrum (active ingredient in Flit), but it has no residual action. And also by residual spray of resting places of adults (walls0 using an insecticide of long action (residual insecticide) eg, hydrocarbons as DDT and Gammaxane, Organophosphorous compounds as Malathion and Diphterex, carbamates as sevin. The dvelopment of resistance is a drawback of insecticides
Specific agents can be applied against aquatic stages. These agents are applied to water surfaces. Anopheline larvae are affected more than culicines, being surface feeders. Pupae are not affected, as they do not feed. Respiratory poison: applying non-volatile oils suffocates larvae and pupae by blocking the respiratory spiracles. Residual insecticides are sprayed on water surface mixed with dust or oil. They exert their effect by contact and ingestion. Practically no single method alone is efficient in control. The combined use of two or more methods (integrated control) would provide a higher and more efficient level of abatement. Insects escaped on method, are killed by other.
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