Mosquitoes

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Mosquitoes
Yellow fever mosquito (Aedes aegypti)

Yellow fever mosquito ( Aedes aegypti )

Systematics
Class : Insects (Insecta)
Order : Fly (Diptera)
Subordination : Mosquitoes (Nematocera)
Partial order : Mosquito-like (Culicomorpha)
Superfamily : Culicoidea
Family : Mosquitoes
Scientific name
Culicidae
Meigen , 1818
Subfamilies

Mosquitoes (Culicidae) are a family of insects within the order of the fledglings . There are more than 3,600 mosquito species worldwide. There are 104 species in Europe, almost all of which can also be found in Central Europe.

With the help of a specialized mouth tool , the stinging- sucking proboscis , female mosquitoes can pierce the skin of their hosts and suckle blood . The proteins (especially from hemoglobin and albumin ) and iron (from porphyrin compounds such as heme ) absorbed with the blood meal are essential for the production of eggs . Otherwise, female mosquitoes as well as males feed on nectar and other sugary vegetable juices. Different mosquito species can specialize in different hosts or host groups. Certain mosquitoes are important carriers of infectious diseases such as malaria or dengue fever .

The genetically oldest mosquito known to date is preserved as an inclusion in an amber fossil that is around 79 million years old . A more original sister species of the mosquito is found in 90 to 100 million year old amber.

In large parts of Austria mosquitoes are called gels , in parts of Switzerland and southern Germany Staunsen , Stanzen or Schnaken . The latter is in contrast to the name Schnaken in zoology, under which the species of another family of the two-winged birds are summarized, which do not suck blood. The name mosquito, which is now quite frequently used, is derived from the Spanish and Portuguese word mosquito (literally: little fly ), which also means mosquito . Other blood-sucking insects should be distinguished from mosquitoes .

Occurrence

Mosquitoes are widespread all over the world, they are only absent in Antarctica and on some isolated oceanic islands, such as Iceland . Large swampy areas in particular, such as the tundra and taiga, are ideal breeding grounds for the mosquito. However, the different species have very different ranges. In Germany, Austria and Switzerland, besides other occurring species, the common mosquito and the somewhat larger marigold are particularly common .

features

The yellow fever mosquito Stegomyia aegypti , a member of the subfamily Culicinae . On the left the male, on the right the female. The male has bushier antennae and longer palps . On the right a resting yellow fever mosquito - normally the animals sit on vertical surfaces with the head up, the hind legs are always raised in this species when sitting. At the top left, a schematic diagram of a flying couple during mating.

Adult mosquitoes are slender, two-winged insects of different sizes, depending on the species and diet of the juvenile stages, but rarely larger than 15 millimeters. Their wings are membranous, partly scaly, and as two-winged birds they have two swinging bulbs or holders . Their antennae are medium-long and multi-jointed, they have a proboscis about as long, a slender body and long legs. Mosquitoes weigh about 2 to 2.5 milligrams.

The males are usually smaller than the females. You can recognize them mainly by their bushier antennae. Female representatives of the subfamily Culicinae also have palps , which are considerably shorter than the proboscis. In representatives of the subfamily Anophelinae , the palps are about as long as the proboscis in both sexes.

Mix-ups

There is a possibility of confusion with other two-winged birds , especially midges , tufted mosquitoes and meadow flies , which look like mosquitoes but do not suck blood.

Flight characteristics

Mosquitoes can fly at speeds of around 1.5 to 2.5 kilometers per hour. The flight altitude of a mosquito generally depends on the species in question, on the altitude of its location above sea level, on the weather, the air pressure, the temperature and the light conditions. The mosquito's activity is greatest in warm, windless weather with light cloud cover and no direct sunlight. Then some species can also reach great flight altitudes by being carried by thermal updrafts at heights of over 100 meters above the ground. In cool or rainy weather, many mosquitoes only fly short distances and tend to stay close to the ground. If there is clear wind and temperatures in the freezing point range , they completely stop flight activity.

Researchers at the Georgia Institute of Technology found that mosquitoes, thanks to their small mass, can survive collisions with raindrops . They can cope with accelerations between 100 and 300 g , according to the study "the highest accelerations in the animal kingdom".

nutrition

Enlargement of a blood-sucking mosquito with the short mouth probes typical of the female representatives of the subfamily Culicinae . The red-orange bundle of stinging bristles, in the picture to the right of it the lower lip, compressed backwards and not penetrating the
skin .

After being fertilized by the males, the females must have a meal of blood to produce eggs ; The uptake of blood and the protein it contains is therefore essential for the reproduction of most mosquitoes. The blood meal is taken with the help of a proboscis . Different mouthparts form a structure of pierced bristles (upper lip or labrum , paired upper and lower jaw or mandible and maxilla as well as pharynx or hypopharynx ). This bundle of stinging bristles can penetrate the host's skin and forms two channels inside. One can inject saliva and the other can suck up blood. In the rest position, the piercing bristles are hidden in a sheath formed by the lower lip labium . When you prick, the lower lip itself does not penetrate the skin, but is compressed and bends backwards.

The males, on the other hand, do not suck blood. Your piercing bristles are shortened, unsuitable for a prick and only serve to suck up exposed liquids.

Sugary plant juices are consumed by both females and males to meet their energy needs. The most important source of carbohydrates is nectar , with certain sources of nectar being preferred to others. So far, however, they have only been described as effective pollinators of plants for two species: the orchid habenaria (Platanthera) obtusata and the clove herb Silene otites , a carnation plant . Certain fragrances produced by the flowers also seem to be attractive to mosquitoes.

An exception to the rule that female mosquitoes need blood for the production of their eggs are the females of the genus Toxorhynchites , whose mouthparts are not suitable for the bite of a blood host. The larvae of this genus eat other mosquito larvae and are therefore able to take in and store enough protein for egg production as an adult female as early as a youth. Also with other strains or species such as Culex pipiens molestus it can happen that females produce a first clutch without a blood meal (autogeny) in which the number of eggs is significantly reduced. In some cases it is even possible that more than just one autogenous clutch is produced.

Finding the food source:

Laboratory and field experiments have shown that mosquitoes mainly find their blood hosts through exhaled carbon dioxide and body odors (e.g. various fatty acids and ammonia ). Depending on the species and host specificity, individual substances can be of particular importance. For example, in the case of the human-specialized yellow fever mosquito ( Aedes (Stegomyia) aegypti ), the lactic acid appearing on the human skin is a central stimulus for finding a host.

When finding a host, the mosquitoes follow the scent plume of their host to their source. In addition to the chemical composition of the odor plume, its size, structure and shape apparently give the mosquito important information about the host and its removal. At close range, visual cues and body heat also play a role.

Copulation

Many mosquito species mate in stationary swarms that are formed at certain times of the day (often at dusk). These mating swarms can consist of thousands of individuals; this also depends on the species. The individual participants fly in loops or zigzag movements and usually orient themselves on conspicuous landmarks. The swarms are mostly made up of males. Species-specific fragrances ( aggregation pheromones ) may play a role in the formation of swarms and in attracting the females .

Approaching females fly into the flock and are mated. The males orientate themselves mainly on the humming sound of the females, which they perceive with the help of special hearing organs at the base of their bushy antennae ( Johnston organ ). Although the antennae of the females seem to be less suitable for receiving sounds, it has meanwhile been shown that the females also react to the flapping sound of the wings of the males - both partners adjust the height of their flight tones as they approach each other.

A large number of other insects also form mating swarms. Most swarms found in summer are formed by mosquitoes, for example.

development

The life of a mosquito is divided into four different stages: egg , larva , pupa and imago (the adult animal).

egg

Depending on the species, the eggs are either laid individually ( e.g. Aedes or Anopheles ) or in egg packets or boats ( e.g. Culex ). They are placed on the surface of the water or near the water. Most species prefer stagnant water. Sometimes even the smallest amounts of water, such as in tree hollows, rock hollows, bromeliads or similar reservoirs, are sufficient. Often the eggs of mosquitoes with such egg-laying biotopes are drought-resistant and can survive drying out (for example yellow fever mosquito or Asian tiger mosquito ). The genus Wyeomyia also lays its eggs in the catchers of insectivorous pitcher plants, representatives of the genus Deinocerites usually use the water accumulations at the end of the burrows of certain land crabs.

Many representatives of the mosquito lay their eggs in moist or swampy biotopes, the larvae then hatch in a flood (for example the meadow or alluvial forest mosquito Aedimorphus vexans and Ochlerotata sticticus or other native representatives of the genus). In this case, the egg is usually the hibernating stage.

larva

Lateral view of mosquito larvae , hanging from the surface of the water in their
feeding position : A: Anopheles (subfamily Anophelinae); B: Culex (subfamily Culicinae)

There are four larval stages . Mosquito larvae live exclusively in water, but breathe atmospheric air. Representatives of the subfamilies Culicinae have a more or less long breathing tube on the eighth segment of the abdomen, through which they breathe while hanging on the surface of the water. As an exception, larvae of the genus Mansonia tap into the air-filled intercellular spaces of plants with their tooth-reinforced breathing siphons and are thus independent of the water surface. In the subfamily Anophelinae , the larva hangs horizontally under the surface of the water and breathes through an opening that is also located on the eighth segment of the abdomen.

Detritus and microorganisms serve as food, which is swirled in with the help of brush-like mouthparts and then eaten. The larvae of the genus Toxorhynchites , on the other hand, live predatory on other mosquito larvae. If there is a shortage of food, these larvae even develop cannibalism , which is why there is rarely more than one fully grown larva of a type of Toxorhynchites in the narrow breeding grounds - mostly bamboo stumps in the tropics .

In the event of a disturbance, mosquito larvae quickly emerge from the surface of the water. They move in a meandering or twitching manner and with the help of row-shaped tufts and fans of hair.

The duration of the larval stage depends on the species, the temperature and the nutrient content of the larval biotope.

Depending on their juvenile habitats, certain mosquito species can overwinter as larvae (for example Mansonia ).

Doll

With the fourth moult, the pupa hatches , which does not eat any food as it is resting. At this stage the animal breathes, usually also on the surface of the water, through two horns on the prothorax . The genus Mansonia is the exception here; their pupae also draw air from plants.

Mosquito pupae are mobile and can quickly submerge and flee from the surface of the water in case of danger.

The pupa rest is usually short, after a few days the adult animal hatches.

Imago

The imago (the adult insect) hatches from a dorsal crack in the pupal skin within a few minutes and is able to fly after about an hour. Males often hatch earlier than the females.

Many Anopheles species and the genera Culex and Culiseta overwinter in our latitudes as mated females in cool, moist and protected places, for example in cellars, caves or cattle sheds. The males die in autumn.

Mosquitoes as carriers of disease

In the case of a bite, pathogens ( viruses , bacteria and single-cell or multicellular parasites ) that the mosquito has ingested during a previous meal can also be transmitted with the mosquito's saliva . It is important that the pathogens also multiply in the mosquito after being bitten by an infected host and get into the salivary glands. To do this, the pathogens or their specialized intermediate stages must also infect the mosquito. This is why not every mosquito can transmit every pathogen. In mosquitoes and other disease vectors, the time between ingesting a pathogen and being able to pass it on is called the “ extrinsic incubation period ”. It depends on the temperature and usually lasts between 10 and 14 days. If an infected vector stings a host before the extrinsic incubation period has expired, the disease cannot yet be passed on.

As with all vectors, mechanical transmission through pathogen adhesion (contamination) of the mosquito's proboscis is also potentially possible if the insect is disturbed while feeding on an infected person and immediately continues to suckle on another uninfected person. In practice, however, a significant amount of pathogen is required for infection. It is questionable whether this minimum amount can be achieved on its own, for example in the event of contamination of the proboscis. Epidemiologically, there are no clear indications of this type of transmission, at least among mosquitoes.

The most important pathogens transmitted by mosquitoes include plasmodia ( malaria ), parasitic worms living in the lymphatic or blood vessel system ( filariasis , dirofilariasis ), viruses ( yellow fever , dengue fever , West Nile fever , Chikungunya fever , Rift Valley fever ) or bacteria ( Tularemia ).

Mosquito-borne diseases are also common in Europe. West Nile fever and chikungunya fever are among the best known. The less prominent mosquito-borne viral diseases include the Sindbis virus found in Scandinavia and Karelia , which can cause skin rashes and persistent joint pain. Depending on the subtype of the virus, the resulting disease is called Ockelbo's disease in Norway and Sweden, Pogosta's disease in Finland and Karelian fever in the Russian part of Karelia. Due to climate change, it can be assumed that there is an increasing risk of infection by mosquitoes in Germany.

Human body reactions caused by the sting

Sensation of pain

When a mosquito bites, a very slight pain sensation can occur if the proboscis (proboscis) penetrating the skin hits or grazes a pain nerve and the food victim in question is aware of the bite. However, in humans with regard to the case then perceived pain intensity play in this regard in the brain of the sting witnessed stored prior experience and emotional evaluations a role.

Body reactions and treatment

A short time after the sting, an allergic reaction usually limited to the puncture site occurs . This is usually associated with more or less severe itching . Both are caused by the proteins, which injects the mosquito into the suction point to the clot to prevent blood. Often forms at the injection site for a few hours a wheal . These wheals arise after the bite through the release of the body's own histamine .

Antihistamines applied to the irritated area have no proven soothing effects. However, several scientific studies have shown that prophylactic administration of oral antihistamines can suppress the allergic reaction. In the case of a high mosquito load, such preventive treatment can be useful for high-risk patients.

Fighting the mosquito

A hand stung by mosquitoes
A back stung by mosquitoes

The fight against mosquitoes has a long tradition. It began as a side effect of draining wetlands in prehistory. It has also been known for a long time that a film of oil on the breeding waters leads to asphyxiation of the larvae. This environmentally harmful method is still used today. Extensive spraying with the pesticide DDT , which is banned in industrialized countries, is also used in many countries to combat malaria.

The bacterium Bacillus thuringiensis israelensis (BTI) has been used along the Upper Rhine by the communal action group to combat the snake plague (BTI) to control mosquitoes (especially Aedimorphus vexans , which is also known as the Rhine Schnake in this area). The agent is applied over a large area with a helicopter as ice granules and leads to the death of the mosquito larvae by damaging the digestive tract. This type of control is now also used in other regions of Germany (for example on the Chiemsee ).

The most important procedure in normal housing estates is the regular emptying of rain barrels or small pools of water or their covering. In the garden pond, the development of mosquitoes can be hindered, for example, with fish. However, fish also eat other water dwellers that are desirable in a garden pond that is as diverse as possible and that in turn are predators of mosquitoes. Adult dragonflies (Odonata) also hunt adult mosquitoes; Dragonfly larvae can have a decreasing effect on the number of mosquito larvae. The larvae and adults of the back swimmers (Notonectidae), the swimming beetles (Dytiscidae) and certain water friends (Hydrophilidae) also eat mosquito larvae.

There are also various individual insect protection measures that can be used to protect yourself from mosquito bites.

Ecological aspects

A laboratory study showed that the first and second larval stages of the harmless mosquito Chironomus riparius in particular were affected by concentrations of the biological mosquito larvicide Bti that are significantly below the concentrations used in the field. Mosquitoes are an important source of food for other insects and vertebrates because of their widespread distribution and high population numbers in floodplain areas.

In the tundras of the world, the enormous swarms of mosquitoes play a role in the annual migration of the reindeer by causing the animals to climb higher and higher into the mountains. Without these cyclical migrations, the delicate tundras of the far north would be overgrazed very quickly. A presumed great importance of the pollination function, especially in the flower-rich and mosquito-rich, but bee-poor tundras of the north has not yet been conclusively investigated.

Genetic Approaches

With the help of genetic engineering , various approaches to combating mosquitoes have been developed. One strategy is the release of genetically sterile males who, after mating with females, produce non-viable offspring ( autocidal or sterile insect technique). Another strategy involves introducing disease-insensitive genes into mosquito populations so that they can no longer transmit diseases.

Species and genera (selection)

Subfamily Anophelinae

Subfamily Culicinae

See also

literature

  • N. Becker et al: Mosquitoes and their Control . Kluwer Academic / Plenum Publishers. New York / Boston / Dordrecht / London / Moscow 2003, ISBN 0-306-47360-7 .
  • Heiko Bellmann, Klaus Honomichl, Werner Jacobs, M. Renner: Biology and ecology of insects: A pocket dictionary . 4th, revised edition. Elsevier Spektrum- Akademischer Verlag, Heidelberg 2007, ISBN 978-3-8274-1769-5 .
  • M. Chinery: Parey's Book of Insects . Kosmos, Stuttgart 2004, ISBN 3-440-09969-5 .
  • JD Gillett: The Mosquito: Its Life, Activities and Impact on Human Affairs . Doubleday, Garden City 1972, ISBN 0-385-01179-2 .
  • W. Lechthaler: Culicidae - Key to Larvae, Pupae and Males from Central and Western Europe. Determination software on CD-ROM. Eutaxa self-published, 2005, ISBN 3-9501839-2-2 .
  • E. Martini: About mosquitoes, especially their European species and how to control them. JA Barth, Leipzig 1920.
  • Werner Mohrig: The culicids of Germany. Studies on the taxonomy, biology and ecology of the native mosquitoes (= Parasitological series of publications. Issue 18). G. Fischer, Jena 1969.
  • F. Peus: Mosquitoes. (= Die Neue Brehm - Bücherei. Volume 22). Hohenwarsleben 2003, ISBN 3-89432-516-X . (Reprint of the 1951 edition by Westarp-Wissenschaften-Verlagsgesellschaft)
  • A. Rose, M. Geier: Why it is useful to lure the enemy: Mosquitoes led astray. Mosquitoes as carriers of disease. In: W. Fürst, J. Bauernschmitt (Ed.): Biotechnology in Bavaria. Media Mind, Munich 2004, pp. 64–68 (PDF file 145 kB).
  • F. Schaffner among others: The Mosquitoes of Europe / Les Moustiques d'Europe. Determination software on CD-ROM. IRD Éditions, Paris & EID Méditeranée, Montpellier 2001, ISBN 2-7099-1485-9 .
  • A. Spielman, Michael D'Antonio : Mosquito: A Natural History of Our Most Persistent and Deadly Foe . Hyperion Press, New York 2001, ISBN 0-7868-6781-7 .
  • R. Réaumur: The mosquitoes. In: J. Soentgen, M. Schweiger (ed.): René-Antoine Ferchault de Réaumur 1683-1757: Insects. A selection. Translated and compiled by Friedrich Koch. University of Augsburg, Augsburg 2014, pp. 64–85 ( PDF file; 1987 kB )

Web links

Commons : Mosquitoes  - Collection of images, videos and audio files
Wiktionary: Gelse  - explanations of meanings, word origins , synonyms, translations
Wiktionary: Mosquito  - explanations of meanings, word origins, synonyms, translations

Individual evidence

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  2. Culicidae in Fauna Europaea
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