mosquito

See text. The females of most mosquito species suck blood from other animals.

Mosquitoes are believed to have evolved around 170 million years ago during the Jurassic era (206–135 million years ago) with the earliest known fossils from the Cretaceous era (144–65 million years ago). Ancestral mosquitoes were about three times the size of the extant species and they are a sister group to the Chaoboridae (biting midges).

Mosquitoes are principally nectar feeders with only the females requiring a meal of blood, except for the Toxorhynchites, which never drinks blood. This family includes the largest of the extant mosquitoes (colloquially referred to as "mosquito eaters"), the larvae of which are predatory on the larvae of other mosquitoes. These mosquito eaters have been used in the past as mosquito control agents with variable success.

The female mosquito (in almost all species) sucks the blood of mammals, including humans. Mosquito bites often swell up hours after happening, causing a red ringed white bump about a centimeter in diameter. Mosquito bites can transmit diseases, such as malaria and West Nile Virus, so authorities in many areas take measures to reduce mosquito populations through pesticides or more organic means. An easy way to reduce mosquito populations in a residential area is the removal of standing water (where mosquitoes breed), and the use of repellents, such as DEET.

Natural history

In most female mosquitoes, the mouth parts form a long proboscis for piercing the skin of mammals (or in some cases birds or even reptiles and amphibians) to suck their blood. As opposed to a syringe's typically smooth needle, the mosquito proboscis is highly serrated, which leaves a minimal number of points of contact with the skin being pierced — this reduces nerve stimulation to the point where the "bite" is not felt at all, which is generally the case (see the Mosquitoes and health section below for an explanation on the swelling).

The mosquito undergoes complete metamorphosis, going through four distinct stages in its life cycle: egg, larva, pupa, and adult — a process that was first described by the Greek philosopher Aristotle. Many species of mosquito live their adult stage in roughly two weeks to two months. Most larvae feed on microorganisms, but a few are predatory on other mosquito larvae.

Most mosquito species outside of the tropics overwinter as eggs, but a significant minority overwinter as larvae or adults. Empirical studies of mosquito bites suggest that the risk of being bitten follows an approximately negative binomial distribution.

Mosquitoes and health

In much of the world, mosquitoes are a major public health problem; In the United States, Australia, New Zealand, the UK, Scandinavia, and other temperate countries, mosquito bites are mostly just a nuisance.

The mosquito genus Anopheles carries the malaria parasite (see Plasmodium). Most species of mosquito can carry the viral diseases yellow fever, dengue fever, epidemic polyarthritis, Rift Valley fever, Ross River Fever, and West Nile virus.

A mosquito's period of feeding is often undetected; When a mosquito bites a human, she injects saliva and anti-coagulants. Some adults can become desensitized to mosquitoes and have little or no reaction to their bites, while others can become hyper-sensitive with bites causing blistering, bruising, and large inflammatory reactions.

Mosquitoes in flight emit a distinctive high-pitched buzz, which can interrupt sleep.

Mosquito control and integrated mosquito management

There are two kinds of mosquito control: large, organized programs to reduce mosquito populations over a wide area, and actions individuals can take to control mosquitoes with respect to themselves and their own property.

Organized mosquito control programs today draw on the principles of integrated pest management. An integrated mosquito control program typically includes the following measures, all guided by surveillance of mosquito populations and knowledge of the mosquito life cycle:

Since many mosquitoes breed in standing water, source reduction can be as simple as overturning an old tin can, or can be as complex as permanently draining marshes. Eliminating such mosquito breeding areas can be an extremely effective and permanent way to reduce mosquito populations without resorting to insecticides.

Habitat modification, such as ditching or diking marshes or manipulating daily water flows can be effective at reducing mosquito populations by disrupting the mosquito life cycle, but experience has shown that such large-scale programs can be harmful to the ecosystem if not undertaken carefully. One example of a successful approach to habitat modification, open marsh water management, involves the use of shallow ditches to connect the shallow waters where mosquitoes breed to deeper waters where natural predators live. Simply giving the predators access to the mosquito larvae can result in long-term mosquito control.

Biological control or "biocontrol" is the use of natural enemies to manage mosquito populations. There are several types of biological control including the direct introduction of parasites, pathogens and predators to target mosquitoes. Effective biocontrol agents include predatory fish that feed on mosquito larvae such as Gambusia affinis and other minnows and killifish. In particular, there is no documented study that establishes that bats or purple martins consume enough mosquitoes to significantly control mosquito populations (see Kale 1968).

Like all animals, mosquitoes have their own set of diseases. Microbial pathogens of mosquitoes include viruses, bacteria, fungi, protozoa, nematodes, and microsproidia (Davidson 1981, Jahn 1986)

Also used as biological control agent are the dead spores of varieties of the natural soil bacteria Bacillus thuringiensis, especially Bt israelensis (BTI). A chemical commonly used in the United States is methoprene, considered slightly toxic to larger animals, which mimics and interferes with natural growth hormones in mosquito larvae, preventing development.

Adulticide, the ground or aerial application of chemical pesticides, is less effective than the other methods of mosquito control and is generally considered a method of last resort. For example, ultra low volume (ULV) spraying of Malathion has been used in metropolitan areas like New York City to decrease the mosquito population and prevent the spread of West Nile Virus.

The most effective solutions for malaria control efforts in the third world are: mosquito nets (klamboe), mosquito nets treated with insecticide (often permethrin), and DDT. Insecticide-treated nets (ITN) are estimated to be twice as effective as untreated nets in preventing mosquito bites. Untreated mosquito nets are less expensive, and they are effective in protecting humans when the nets do not have any holes and are tightly sealed around the edges.

The role of DDT in combating mosquitoes has been the subject of considerable controversy. While some argue that DDT deeply damages biodiversity, others argue that DDT is the most effective weapon in combatting mosquitoes and hence malaria.

Mosquito repellents and personal mosquito control

Mosquito repellents generally contain one of the following active ingredients: DEET, catnip oil extract, nepetalactone, citronella, or eucalyptus oil extract.

Other popular methods of household mosquito control include use of small electrical mats, mosquito repellent vapour, and mosquito coil, all containing a form of the chemical allethrin. Mosquito repellent candles containing Citronella oil is another method to keep mosquitoes at bay. Some lesser known methods use the cultivation of plants like wormwood or sagewort, lemon balm, lemon grass, lemon thyme and the mosquito plant (Pelargonium) which act against mosquitoes.

There are several widespread theories about mosquito control such as the assertion that Vitamin B, in particular B1 Thiamine, garlic, ultrasonic devices, incense, bats, purple martins and bug zappers can be used to repel or control mosquitoes . Whether these methods are effective at deterring mosquitoes or significantly reducing mosquito populations remains disputed.

Although bats can be prodigious consumers of insects, many of which are pests, less than 1% of a bat's diet will consist of mosquitoes; Similarly, bug zappers kill a wide range of flying insects including many beneficial insects as well as mosquitoes;

Some newer mosquito traps emit a plume of carbon dioxide together with other mosquito attractants such as sugary scents, lactic acid, octenol, warmth, water vapor and sounds. By mimicking a mammal, these factors draw female mosquitoes toward the trap, where they are typically sucked into a net or holder where they collect. According to the American Mosquito Control Association , "these devices will, indeed, trap and kill measurable numbers of mosquitoes," but their effectiveness in any particular case will depend on a number of factors such as the size and species of the mosquito population and the type and location of the breeding habitat.

Treatment of mosquito bites

Visible, irritating bites are due to an immune reaction, i.e., hypersensitivity. Some of the sensitizing antigens are common to all mosquito species, whereas others are specific to certain species. III) and delayed hypersensitivity reactions (Type IV) to mosquito bites (see Clements, 2000).

Cultural Views

Japan

According to the “Mosquitoes” chapter in Kwaidan: Stories and Studies of Strange Things, by Lafcadio Hearn (1850-1904), mosquitoes are seen as reincarnations of the dead, condemned by the errors of their former lives to the condition of Jiki-ketsu-gaki, or "blood-drinking pretas".