Mosquito Types and Lifecycle
Mosquitoes are classed as the most deadly animal in the world, responsible for around a million deaths a year. Happily for those of us in the UK, mosquitoes do not generally transmit deadly diseases here. But still, mosquitoes are irritating, quite capable of seriously reducing the enjoyment of a summer barbecue or a walk in the woods. There are also concerns about one species of mosquito, the Asian Tiger mosquito which transmits several diseases, becoming established in the UK.
Understanding a pest is key to finding the most effective way of controlling it. When it comes to mosquitoes, knowing about their life cycle is a good starting point.
And this is where we come in! Let’s start off with...
The life Cycle of a Mosquito
Female mosquitoes lay eggs after eating a blood meal. Eggs are laid singly or in groups known as rafts and either directly on the surface of still water, around water margins or sometimes in tree holes. The exact location and number of eggs laid depends on the species. When not placed directly on the water, eggs are placed in positions where they will be exposed to it through flooding, irrigation or rain. Eggs can remain dormant for months or even years until the right hatching conditions of sufficient moisture and the right temperature range are met. Many mosquito species overwinter as eggs.
When the right conditions are met, mosquito eggs hatch and larvae emerge. Larvae live in water but close to the surface as they need to breathe air. Most often mosquitoes larvae hang just beneath the surface suspended by water tension. As larvae mosquitoes feed and grow, they moult several times. The larval stage of the mosquito life cycle lasts between 4 and 14 days depending on the species, the temperature, and the availability of food. Some mosquito species overwinter as larvae, though this is less common than overwintering as eggs.
This third stage of the mosquitoes life cycle also takes place in water. The pupa still needs to breathe air but employ a 'tumbling' motion to move between the surface and to deeper water where they are safer from birds that prey upon them. The pupa stage lasts between 1.5 and 4 days, again depending on species and water temperature.
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When the pupa has matured, the casing enclosing it splits along the back and the adult mosquito emerges. Male mosquitoes generally emerge first and remain near the hatching ground to mate with the new adult females. It is only in the adult stage that mosquitoes bite humans, spread disease and wreak havoc upon humanity and other species.
Most mosquitoes don't live for very long. Their natural lifespan depends on the species and can vary from a few days to a few months. Some species only survive a single summer, the adults die as the temperature drops, leaving their eggs behind to restart the cycle the following year. In a few species, the adult female hibernates during the winter, seeking a sheltered location when the weather turns cold and entering hibernation with fertilized eggs inside them.
Few mosquitoes survive the full length of their potential lifespan, as the majority are eaten by predators. The main predators of adult mosquitoes include birds, dragonflies and spiders. Various species of fish, including goldfish, guppies, bass, bluegill, catfish and the Gambusia affinis, which is commonly called the mosquitofish, prey on mosquito eggs and larvae. Humans, of course, do their very best to reduce the population of mosquitoes employing a range of control measures at all stages of the mosquitoes' life cycle.
Male vs female mosquitoes
Any mosquito you can hear is female, their wings beat at around twice the rate of male wings and it's this high rate of movement which generates that annoying buzzing sound. The mosquito that just bit you is definitely female, as male mosquitoes don't bite. Males live for only around 7 to 10 days and feed entirely on plant nectar. Female mosquitoes also feed partially on nectar but need a blood meal in order to lay eggs.
There are a number of other differences between male and female mosquitoes. These are so marked that it's possible to distinguish the two by sight. Male mosquitos are only half the size of their female counterpart and their antennae are covered with fine hairs, to the extent that they look bushy to the naked eye. These fine hairs, correctly known as flagella are used by the male to hear the female which he's looking for her to breed.
Mosquito species in the UK
There are around 34 species of mosquito, which are native to the UK. Many, but not all, types of mosquitoes bite humans.
Asian tiger mosquito
As the name implies this species originates from Southwest Asia. It was introduced in Europe through the transport of goods and has spread through Southern Europe and, in our warming climate, has been gradually moving north at the rate of around 93 miles a year.
A few sightings of the tiger mosquito have been reported in the UK, though they do not as yet appear to have established breeding colonies. The tiger mosquito has a distinctive striped appearance but is by no means the only striped mosquito. It is sometimes confused with two native British mosquitoes, Culiseta annulata and Aedes geniculatus.
The tiger mosquito is capable of carrying parasites, which give rise to a range of serious diseases of both humans and animals. Tiger mosquitoes in the UK have the potential to act as a vector of Zika, dengue fever and the West Nile virus all of which affect humans and Eastern Equine Encephalitis.
While there is not, as yet, a problem with these diseases in the UK, the potential does mean that general mosquito control methods, such as eliminating standing water around the home, clearing blocked gutters, cleaning water butts regularly, changing the water in birdbaths frequently and ensuring that flower pots and wheelbarrows are stored dry are more important than they ever have been. Everyone should take measures to reduce breeding opportunities for mosquitoes, anyone suspecting sightings of Asian tiger mosquitoes is advised to contact a pest control expert so that a professional evaluation and, if necessary, an action plan for elimination can be made.
Common house mosquito
The mosquito generally referred to as the common house mosquito in the UK is Culex pipiens. This is a brownish insect with beige bands over the abdomen, and evenly coloured grey wings and dark legs. In size, the female is around 4-10 mm. The larvae of this species are capable of surviving in heavily polluted water, while the adults overwinter in homes.
The common house mosquito does have the potential to be a vector for disease, including West Nile disease. It should be emphasised that there have been no reported cases of anyone catching this disease as a result of a mosquito bite in the UK, though there have been outbreaks in humans in Southern Europe, notably Greece, Romania and Italy. Generally speaking, as our climate warms, the potential for insect-borne disease in general and mosquito-borne disease specifically increases and there are species of mosquito native to the UK, which are potential disease carriers.
Midge vs mosquito - What is the difference?
These two species are often mistaken for each other in the USA, and confusingly, if you look at USA information, it will often tell you that midges don't bite, or at least that midges don't bite humans. As anyone who has ever ventured outdoors in the Scottish Highlands in the summer can tell you, here in the UK, midges DO bite. There are in fact 35 different species of biting midges in the UK and their bite can be painful, causing intense redness, swelling and itching. The insects referred to as midges in the UK are smaller than mosquitoes, often around 2-3 mm, and unlike mosquitoes, which are solitary, midges attack in packs. However, while midge bites can be painful and while some few people can develop an allergic reaction to them, midges do not carry diseases.
- There are over 30 species of mosquitoes in the UK, not all bite humans, but many do.
- Basic mosquito control measures centre around not providing breeding grounds for them by eliminating standing water.
- Some species of mosquito, which are not native to the UK, are becoming more prevalent here as our climate changes.
- The most concerning change centres around the growing prevalence of Asian tiger mosquitoes.
- There is not currently a significant problem with a mosquito-borne disease in the UK, but the potential for this to develop exists.
- If your own mosquito control methods fail or if you suspect you have tiger mosquitoes local to you, seek advice from a pest control professional.