Mosquitoes

Brief:

Mosquitoes are best known for the blood sucking habit of the female and their potential as a threat to health and comfort of humans and livestock. The characteristic buzzing in the quiet of the night and ‘bites’ that lead to irritating lumps are also well known.

Habits

The mosquitoes pest status is best known for their irritating ‘bites’ which is the term applied to the piercing and sucking feeding action of the adult females. ‘Biting’ can be so irritating and annoying it can lead to reduced yield in animals; humans find the noise of flying mosquitoes annoying and some individuals react severely to bites which become swollen, itchy lumps.

Mosquito eggs are usually laid on the surface of water and hatch into larva, which are aquatic and usually referred to as wrigglers. Larvae feed on organic matter, which they filter from their environment.  The larvae undergo four moults before pupating. The adult emerges from the pupal case onto the surface of undisturbed water. The life cycle from egg to adult may be as short as a week, or much longer depending upon temperature, food supply, species etc.

Males have a short life and feed on honeydew, nectar and other plant secretions. Females may live for several weeks and may pierce the skin of a variety of animals in order to suck blood.

Habitat

Mosquitoes are very skilled at finding and exploiting a range of water bodies, which include but are not confined to natural and artificial water bodies, of permanent or temporary nature and can be fresh, brackish or saline (depending on the species of mosquito). They may include lakes, streams, pools, swamps, dams, irrigation ditches and channels, tree holes, non-draining roof guttering, septic tanks, drainage pits, rock pools and water captured in almost any vessel including tins, cans, old rubber tyres, drip trays of pot planes etc. and all may serve as larval habitats.

Adults may stay close to breeding sites or may disperse over several kilometres depending upon the species and other factors. One of the driving factors is the female’s need for a blood meal, to obtain protein before egg production.

Threats

Mosquitoes pose a significant threat to the health and comfort of humans and their animals.

The irritation from the bite arises from the injection of mosquito saliva into the skin that acts as an aesthetic and anticoagulant. The injection of saliva is also import, because it is the route of disease vectors that enter humans and animals; it is this act that causes millions of human deaths each year. A female mosquito ingests the transmitted diseases during a previous blood meal, from an infected person or animal. Once inside the female’s body the disease causing organisms multiply before being passed on to another individual at the next blood meal.

Of the diseases transmitted by mosquitoes, malaria is the greatest killer of humans with the majority of deaths occurring in countries outside Australia (e.g. Papua New Guinea, throughout South East Asia, India, a few countries in the Middle East and Africa).

Malaria is not common in Australia; however the Australian population is often threatened with lesser epidemics such as hemorrhagic Dengue Fever, ‘ordinary’ Dengue Fever, Ross River Fever, and Murray Valley Encephalitis.

The following table shows some of the disease vectors transmitted by mosquitoes and where they breed and when the females are active.

Prevention

The greatest impact individuals can have on mosquito prevention is the disruption of the insect’s life cycle by preventing incidental water accumulation sites that accumulate in rubbish (old tins cans, tyres and any other receptacle that can hold water; blocked roof guttering is another potential water source that can be addressed by homeowners). Where ever possible water accumulated should be drained or avoided.  Where large-scale water bodies are involved governments should have a thorough understanding of the water and mosquito ecology to minimise the opportunity for mosquitoes to breed. Biological control may also be involved through the use of insect eating fish such as Gambusia.

Protection against adult mosquitoes may be afforded by erecting of screening of doors, windows, vents and other openings in buildings.

Others

Pictures and information are provided by Bayer & FMC Australia.

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