Mosquitoes
Where do they come from?
Australia is the world’s largest island. It is a large country with many different climatic conditions ranging from arid to tropical to alpine. As such it is home to about 400 different mosquito species, which can be found across most of Australia. Ten species are commonly abundant and represent a serious pest threat because of their nuisance biting or their ability to transmit disease. Mosquitoes are members of the family Culicidae and evolved some170 million years ago during the Jurassic era. Ancestral mosquitoes were about three times the size of the current species. ‘Mosquito’ is a Spanish word meaning ‘little fly’ and its use dates back to about 1583. Before then, they were called ‘biting flies’ in English, but the term ‘mosquito’ was adopted to prevent confusion with the common house fly.
What do they look like?
Mosquitoes (colloquially called ‘mozzies’) have a slender body, six delicate legs and a pair of scaled wings. Its head is equipped with a projecting proboscis which conceals and protects the long piercing and sucking mouthparts. This biting insect has a complex life as its ’baby’ stage is aquatic and its adult life is spent on dry land with the female mozzie returning to the water in order to lay her eggs. On average the mozzie life span is 2-3 weeks. Both male and female will feed on nectar and plant fluids but it’s only the female that seeks a blood meal and regularly sucks blood because she requires it as a protein source for egg development.
Where are they found?
Mozzies are mostly nocturnal for a number of reasons. They could dry out during the middle of the day and their favourite blood source tends to be active at dawn and dusk. They breed during spring and summer but can breed all year round if the climate and surrounds are ideal. In Australia the weather, rain in particular, plays a significant role in the breeding of mozzies. Generally an increase in rainfall causes an increase in mozzie numbers. The female mozzie needs some water but breeding places vary with species. Foot path puddles, ditches, streams, rivers, flood waters, lakes, marshes, ponds, pools, bird baths, water tanks, dams, live stock water troughs, even play toys left outside in the yard can provide a breeding environment. In fact any implement that can hold standing water such as pot plant saucers, roof guttering and old tin cans can become the breeding ground for the mother mozzie!
How are mozzies born?
They are born because the female mozzie has had a ‘blood meal’. In other words she has bitten a human, animal or bird and sucked their blood. She uses their blood as a source of protein and as a source of energy to lay her eggs. She lays her eggs on top of any water surface, egg numbers ranging between 100- 400 eggs at a time. Eggs hatch within 72 hours. The larvae, depending on food, prevailing conditions and temperature take 7-10 days to mature and from the pupal stage they turn into adult mozzies within 3 days. They then feed, mate and go on to produce eggs for the next generation. The mozzie’s life span, depending on the particular species, can range from 20 days to 5 years
Why do mozzies bite?
If you are bitten the mozzie bite may swell and looks like a red ringed white bump. It can itch for days and over-scratching can cause it to bleed. If the bites become infected with bacteria a secondary infection can be initiated, especially on the lower limbs.
When the mozzie uses a human for her meal she will probe your skin for a blood capillary then inject a small amount of saliva containing chemicals which prevent your blood from clotting. This is how potentially dangerous pathogens such as viruses enter your bloodstream. After sucking on your blood, she will find a resting place to digest her meal and develop eggs before flying off to find the necessary pool of water in which she deposits her eggs.
How do I protect myself?
Avoid infested areas especially at dawn and dusk when mozzies are most active, use repellent that contains the chemical DEET reapplying it regularly and wearing long sleeved shirts and pants. The Queensland Institute of Medical Research and the NSW Department of Health recommend protecting yourself with a personal repellent such as RID which uses DEET.
Householders can ensure that their backyards do not contain water holding containers. A stiff breeze keeps the mozzies away so move your picnic or campsite to a windy spot. Mozzies hate the smell of fresh basil and citronella so consider planting these plants around the house.
Remember that preventing the transmission of disease is through reducing the threat of bites!
Why do some people not get bitten?
It is true that some people escape the biting female. The female mozzie uses receptors to locate carbon dioxide (CO2), a chemical given off by humans. She is very attracted to that chemical and can detect it on a human from a distance of 6 meters. The mozzie uses her sensitive receptors to also identify secondary attractants like body odour , scent and heat. These properties are all produced by people and are specific to the individual and are a result of muscle activities, perspiration and breathing. The mozzie is attracted to these specific signals that emanate from humans and animals and birds through skin and breath. Simply put, if you are breathing then you are attractive to the female mozzie. If she doesn’t fancy you just consider yourself lucky!
What diseases are transmitted by a mozzie bite?
Mozzie bites can transmit several diseases. The diagnosis of mosquito-borne diseases can only be confirmed with appropriate blood tests.
Mosquito vector (insect) borne diseases found in Australia are: