Mosquitoes

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Mosquitoes
Chironomus plumosus

Chironomus plumosus

Systematics
Class : Insects (Insecta)
Order : Fly (Diptera)
Subordination : Mosquitoes (Nematocera)
Partial order : Mosquito-like (Culicomorpha)
Superfamily : Chironomoidea
Family : Mosquitoes
Scientific name
Chironomidae
Newman , 1834
Subfamilies
  • Aenneinae †
  • Buchonomyiinae
  • Chilenomyiinae
  • Chironominae
  • Diamesinae
  • Orthocladiinae
  • Podonominae
  • Prodiamesinae
  • Tanypodinae
  • Telmatogetoninae
  • Usambaromyiinae

The mosquitoes (Chironomidae), also known as dancing mosquitoes or swarming mosquitoes , are a family of the two-winged mosquitoes ( Diptera) and belong to the mosquitoes (Nematocera). Around 5000 species of this group of animals live worldwide, around 570 species are known from Germany. These are mostly very small to medium-sized mosquitoes with a body length between two and 14 millimeters.

The mosquitoes are common worldwide and even occur in extreme habitats where other insects do not live. The representatives of the genus Clunio can be found on the oceans and the species Belgica antarctica permanently on the Antarctic continent.

Because of their massive occurrence, mosquitoes are very important in the food chain . Mosquito larvae are the main food for many fish . Adult mosquitoes are used by many birds as basic food for rearing their young.

Characteristics of the mosquito

Like the mosquitoes (Culicidae), the mosquitoes are soft-skinned and filigree. The mouthparts are not suitable for pricking and blood sucking , in many species they are also completely regressed. The antennae are hairy in whorls, so they are well suited for picking up vibrations. These are sent to the Johnston organ and processed there. The chest is highly arched, the wings are usually very well developed. However, they can also be regressed to a greater or lesser extent in one or both sexes (for example in the genus Clunio ).

Way of life of the mosquito

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Most species of mosquitoes feed on nectar and honeydew . The lifespan of the adults is a few days at most.

The mosquitoes owe their name to the fact that they always carry out twitching movements of the front legs, which are freely pointing forward, even when they are at rest (χειρονόμος gesticulator, conductor). The significance of these twitches is unknown. The wings are laid on the body like a roof.

Most mosquitoes form large swarms to find a partner, so-called dance swarms , which can be reminiscent of billows of smoke when they are in large numbers . A deployment of the fire brigade due to these swarms has been proven several times. The swarms consist predominantly - with some species also exclusively - of males and occur, depending on the species, at certain times of the day and predominantly when there is no wind or only weak wind. The males keep climbing up and down in the dance swarms. The species-specific frequency of the flapping of the wings leads to a buzzing sound that attracts females of the same species. These are captured and mated in flight. Simultaneous swarming of different species also occurs, but because of the different frequency within the swarms this does not lead to a mixing of the species, especially since they are at different heights above the ground. Finding a partner within the swarm has not yet been clarified. The selection of the location is also partly unclear, but in some types of swamp methane gases attract and swarm. A water surface is recognized based on the polarized light.

The flight altitude of a mosquito or a swarm is generally dependent on the respective species, on the altitude of its abode above sea level, on the weather, air pressure, temperature and lighting conditions. In warm, windless weather with light cloud cover and no strong direct sunlight, some species can reach a great flight altitude, because they also use thermal updrafts and can thus reach heights of over 100 m above ground in some places. In cool, windy or even rainy weather, many mosquitoes fly only short distances, if at all, and tend to stay close to the ground. This is why certain mosquitoes are considered invertebrate weather fairies, according to which the swallows adjust their flight altitude, as they mostly feed on mosquitoes.

The isolation of the species from each other often takes place through the seasonally different appearance of the adults. For example, seasonal occurrences could be registered at Lake Plön , according to which the animals can be classified. The early spring species (March / April) therefore include Chaetocladius and Trissocladius grandis , the spring species (April / May) are Stietochironomus crassiforceps and Microtendipes pedellus . The summer species (June to August) form Psectrocladius sordidellus and many other species, this is the main hatching time for mosquitoes. Chironomus plumosus was classified as a distinct autumn species (September / October) .

In order to reproduce, the females probably fly visually towards a swarm of males, whereupon the males become very excited. In some species the female is grabbed by a male with her forelegs, coming from above; the copulation begins in the air and is then usually accomplished on the ground. This behavior is also species-specific: in other species the entire copulation takes place in flight, in still others it only takes place on the substrate. Often females fly indiscriminately into a swarm of another species, but species-appropriate copulation is ensured by the fact that the reproductive organs are matched to one another according to the key-lock principle, which is typical for the species. As with most two-winged animals, the sperm is transmitted in the form of a spermatophore .

The females begin to lay eggs immediately after copulation, in some species parthenogenesis also occurs. The eggs are mostly laid at dusk or at night and the laying takes place differently depending on the species. In Chironomus plumosus and Chironomus anthracinus , the egg balls are thrown over the open water surface, the larvae develop in the oxygen-poor deep layers of the water. In other species, the egg balls are attached to any object at the water level or placed on the bank of standing or flowing water. Sometimes the eggs are laid on a moist substrate outside the water. Due to the strong swelling of the gelatinous shell of the eggs, typical egg balls form, which prevent them from drying out, even if they fall dry.

Mosquito eggs
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Mosquito spawn
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The same spawn as in the previous picture 5 days later. Many larvae have already hatched.
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Eggs captured with dark field microscopy .
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Extract from previous picture with higher resolution. The expansion of the germ line can be clearly seen.

Larval development

The larvae

The mosquito larvae are quite uniform in habit. They are all slender, worm-shaped larvae with a head capsule (eucephal). Specific type differently are mouthparts , especially the dentition of the labium and the powerful mandibles . Accordingly, these are mainly used for determination. The body consists of three breast and nine abdominal segments and has a pair of stumpy feet on the first breast segment. On the last segment there is a pusher which , like the stubby feet, can be covered with hooks and bristles, and for species in mountain streams even has a median suction cup. The stub feet and the pusher allow a relatively fast movement on the substrate. Breathing takes place through the skin, the trachea are always closed. In some species, especially those living in oxygen-poor waters, breathing is supplemented by filamentous tubules on the abdomen. Anal papillae for osmoregulation can also be formed around the anus .

To aid breathing, the larvae regularly perform serpentine movements that create a stream of water around the body. Species in oxygen-poor waters, in particular, are usually colored red, as they also use hemoglobin to transport oxygen in their hemolymph and can thus absorb the oxygen dissolved in the water even more effectively. Some species, such as Chironomus riparius , sometimes manage completely without oxygen (anaerobiosis).

Due to the very different way of life, the mosquito larvae are divided into two main groups according to their habitat, the water dwellers (aquatic larvae) and the ground dwellers (terrestrial larvae).

By far the largest number of mosquito larvae live in the water, and many species show an astonishing ability to adapt to the environmental conditions of this habitat. They can be found in fresh water as well as in salt water with up to 37% salinity, also on banks, in the depths of lakes, in glacial lakes, in thermal baths with up to 51 ° C warm water, in mineral springs and in tiny water accumulations in Leaf axils of plants ( Phytotelmata ). Some larvae endure prolonged drying out or freezing due to the storage of glycerine in the hemolymph .

Aquatic mosquito larvae
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The appendices at the rear end (left) are easy to see here.
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Head and front body
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Mosquito larva with hemoglobin in the "blood"
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This larva is about 1 cm long, the head is on the right. Cutouts show the rear end of the same animal. This larva wiggled and floated freely in the water.

Mosquito larvae mostly live in the substrate on the ground or in the growth of stones and plants in the water. Due to their sometimes massive occurrence, they play an essential role as a nutritional basis for predatory arthropods ( crustaceans , water mites and aquatic insects) and also for fish. Many species live in self-made webs, whereby the threads are formed in the salivary glands . Often these tubes, as in the caddis fly larvae (Trichoptera), are covered with substrate elements or stiffened by "skeletal" threads. The larvae of Lithotanytarsus emarginatus often live en masse in lime-rich mountain streams in tubes that are encrusted with lime due to the activity of lime-secreting algae (chironomid tuff).

Aquatic mosquito larvae mostly live on degradation substances in the water and on algae. They get this by grazing the substrate (often diatoms ), but often also by using their web as a safety net in which suspended matter gets caught. This web is then eaten along with its contents about every two minutes and regenerated. Some Psectrocladius species eat thread algae of the genus Spirogyra , the larvae of Cricotopus brevipalpis live as miners in the floating leaves of Potamogeton species, Cricotopus trifasciatus larvae live as deminers on the surface of various aquatic plants. Parachironomus tenuicaudatus eat the empty pupal shells of Chironomus species. Tanypus species and close relatives even live as predators and hunt other insect larvae.

Many midge larvae live on other present in the aquatic insect larvae, for example, where the mayflies , dragonflies , stoneflies , caddisflies , Big Wings or Fly . The interspecific interrelationships range from phoresia through symbiosis to parasitism . Symbiocladius rhitrogenae sits under the wing sheaths of mayfly larvae (Ephemeroptera), there sucks the host's hemolymph and pupates there too. Two Nanocladius species parasitize stoneflies of the species Pteronarcys biloba . Other species can only be carried around by the stonefly larvae in order to get to rich food sources.

Mosquito larvae can also live on or in snails , mussels , corals or sponges . The larvae of the genera Xenochironomus and Oukuriella colonize freshwater sponges and eat their way through the sponge tissue. The larva of Parachironomus varus builds a shell on the houses of the spring bladder snail ( Physa fontinalis ) and feeds on the snail's tissue. It can also spin the opening and thus kill the snail.

Given this ecological diversity, it is understandable that over a hundred Chironomid species (as larvae) can occur next to each other in a stream.

Only species of the subfamily Orthocladiinae live in the soil and in other terrestrial habitats, although they can also be aquatic. Characteristic for these species are shortened antennae, a partial regression of the stump feet and the push-up to hard bulges. The animals have different moisture requirements. Many species live in moist, sometimes even flooded moss cushions such as Pseudosmittia virgo and Bryophaenocladius subvernalis . Paraphaenocladius impensus can be found on flushing fringes and in meadow meadows; Dry moss cushions in roofs or cracks in the pavement are preferred by Bryophaenocladius muscicola and Pseudosmittia and Parasmittia species can be found in humus-rich meadow and forest soil. Finally, Camptocladius stercorarius lives as a coprophage in soft dung. The diet of these species consists of organic particles of various kinds mixed with grains of sand. The transition to rural life has certainly occurred several times in the mosquito species, since the species found there are not closely related to one another. In Pseudosmittia ruttneri a secondary returns to be accepted into the water, because all other species of the genus are country alive.

The dolls

The mosquito pupae are also built quite similarly. Pupation always takes place after four stages. They usually have horns as respiratory organs on the chest (prothoracic horns). These are completely absent in some species, especially in inhabitants of oxygen-rich water or the Clunio species living in seawater, as well as in many terrestrial species. Due to the way of life, the dolls are divided into freely movable forms and housing dolls.

The freely movable dolls have breathing horns with an open connection to the tracheal system. They hang on the surface of the water to breathe and, if disturbed, fall tumbling into the depths. A hair fan on the last abdominal segment serves as a swimming organ. These forms mainly include the members of the subfamily Tanypodinae.

In the dolls that live in housings, the breathing squirrels are simply fingered like tracheal gills, they are always closed against the tracheal system. Pupation takes place in the more or less modified living tube of the larva, whereby this is often shortened and somewhat expanded. In some species it is provided with a sieve-like lid for pupation, which allows the water to pass through. The water is supplied by rhythmic vibrations of the abdomen. Before the imago hatches, the pupa leaves the housing, supported by the movement of the end of the abdomen, and is carried to the bank with the water. In standing water, it swims actively to the surface with the help of the swimming fan or passively rises through an accumulation of air between the doll's skin and the imago. The Imago hatches within a few seconds and flies away. The terrestrial pupae have no problems with hatching. The species hatch at different times of the day. For example, Chironomus thummi hatches during the day, Chironomus plumosus only in the evening.

Most species of mosquitoes only have one generation a year, with the larval stage accounting for the longest and both the pupa and the imago stages only make up a few days. The overwintering takes place as a larva.

Special features of the marine species of the genus Clunio

The species of the genus Clunio and some closely related species develop in seawater, such as the species Clunio marinus , which can be found on the European Atlantic coast. The living tubes of the larvae are located on the rock or sand bottom of the lower intertidal zone. The females of the species are all wingless, the males of most species have well-developed wings, but there are also those with stunted or no wings. The males also have large genital forceps with which the female is grasped and dragged around. It is often pulled out of the doll's shell. However, the female can also hatch alone (except for Clunio aquilonius from Japan). However, reproduction can only take place within the first two hours after hatching from the pupal shell. The meeting is guaranteed by the fact that all adults only hatch on the days immediately after the full or new moon at the time of low tide, with the males a little earlier than the females. The hatching time is controlled by so-called biological clocks . As part of the research into these biological clocks, the genome of Clunio marinus was sequenced.

At Clunio aquilonius Tokun. the male looks for a female pupa on the surface of the water, which can only molt to its imago with the help of the male. This touches the doll with its forefeet, the doll's skin bursts in front and above and in a few seconds the male pulls it backwards with his hind feet and genital pincers. Mating and oviposition take place immediately afterwards, the female dies on the clutch.

Dissemination strategy

Adult swarm mosquitoes themselves can fly, but they only have a small flight radius of about one kilometer. They lose the wings again after a certain time. They expand the radius properly by flying as larvae in the intestines of migratory birds in order to be able to develop new habitats. This is what researchers from the Biological Station in Doñana discovered when examining the excrement of black godwit in a marshland (alluvial land) in Andalusia .

The black-tailed godwit prefers to feed on mosquito larvae and is a migratory bird. On the way south and back, the snipe rests in marshland. The larvae of the swarming mosquito Chironomus salinarius live in the brackish or salt water of the marshland - they are therefore tolerant of changes in the salinity of their surroundings. The researchers found larvae in half of the fecal samples from the birds that made it through the birds' digestive tracts unscathed. In this way, regardless of the season, the larvae get into areas that would otherwise not be accessible to them.

Fossil evidence

The oldest reliable evidence of fossil mosquitoes goes back to a find from a Triassic deposit ( rhaetium ) on the British Isles. However, fossils of this family are primarily known as inclusions in amber and can be found in finds from almost all significant amber deposits. The oldest evidence goes back to the Lower Cretaceous (approx. 130 million years old, Lebanon amber), the most recent to Dominican amber (Lower Miocene to Eocene , 25 to 40 million years old).

Most of the fossil mosquitoes come from the Eocene Baltic amber (40 to 50 million years old). In some significant collections of organic inclusions in Baltic amber, the Chironomidae account for up to 45% of all Nematocera.

Particularly noteworthy is the discovery of a female black fly in Baltic Amber, which is in copula with a mosquito. The antennae of the male mosquito were apparently infested with nematodes , so that the chosen sexual partner could no longer be identified exactly.

See also

Individual evidence

  1. ^ Norbert Becker, Paul Glaser, Hermann Magin: Biological mosquito control on the Upper Rhine. (Festschrift) 20 years of municipal action group to combat the snake plague, 1996, ISBN 3-00-000584-6 , p. 58.
  2. Yasue Inoue, Chiharu Komori, Tadashi Kobayashi, Natsuko Kondo, Ryuhei Ueno, Kenzi Takamura: Nanocladius (Plecopteracoluthus) shigaensis sp. nov. (Chironomidae: Orthocladiinae) whose larvae are phoretic on nymphs of stoneflies (Plecoptera) from Japan. In: Zootaxa. 3931, March 4, 2015, pp. 551-567.
  3. AW Steffan: Larval phoresis of Chironomidae on Perlidae. In: Nature. 213, 1997, pp. 846-847, doi: 10.1038 / 213846a0 .
  4. AW Steffan: Plecopteracoluthus downesi gen. Et sp. nov. (Diptera: Chironomidae), a species whose larvae live phoretically on larvae of Plecoptera. In: Canadian Entomologist. 97, 1995, pp. 1323-1344, doi: 10.4039 / Ent971323-12 .
  5. FO Roque, S. Trivinho-Strixino, M. Jancso, EN Fragoso: Records of chironomid larvae living on other aquatic animals in Brazil. In: Biota Neotropica. 4, 2, 2004, pp. 1-9.
  6. FO Roque, S. Trivinho-Strixino: Xenochironomus ceciliae (Diptera: Chironomidae), a new chironomid species inhabiting fresh water sponges in Brazil. In: Hydrobiologia. 534, 2005, pp. 231-238.
  7. FO Roque, S. Trivinho-Strixino, SRM Couceiro, N. Hamada, C. Volkmer-Ribeiro, MC Christ: Species of Oukuriella Epler (Diptera, Chironomidae) inside freshwater sponges in Brazil. In: Revista Brasileira de Entomologia. 48, 2, 2004, pp. 291-292, doi: 10.1590 / S0085-56262004000200020 .
  8. Tobias S. Kaiser, Birgit Poehn, David Szkiba, Marco Preussner, Fritz J. Sedlazeck: The genomic basis of circadian and circalunar timing adaptations in a midge . In: Nature . doi : 10.1038 / nature20151 ( nature.com ).
  9. ^ Krzeminski & Jarzembowski: Aenne triassica sp. n. the oldest representative of the family Chironomidae (Insecta: Diptera) . In: Polskie Pismo Entomologiczne . tape 68 . Gdynia 1999, p. 445-449 .
  10. George O. Poinar, Jr .: Life in Amber. Stanford University Press, Stanford (Cal.) 1992, ISBN 0-8047-2001-0 .
  11. Wolfgang Weitschat, Wilfried Wichard: Atlas of plants and animals in the Baltic amber. Pfeil-Verlag, Munich 1998, ISBN 3-931516-45-8 .
  12. Friedhelm Eichmann: From life in the amber forest. In: Working Group Palaeontology Hanover. Hanover 2003.

literature

  • K. Honomichl, H. Bellmann: Biology and ecology of the insects. CD-Rom, Gustav Fischer, Stuttgart 1994.
  • Heiko Leuchs: Behavioral activities and pumping capacities of Chironomus larvae (Diptera, Nematocera) as a function of temperature and oxygen supply , [Cologne] 1985, DNB 850752183 Dissertation University of Cologne 1985, 69 pages.
  • Heiko Leuchs, Dietrich Neumann : The behavior of Chironomus larvae (pumping, eating, resting) and its consequences for the exchange of water between sediment and open water. In: Negotiations of the German Zoological Society 78, 1985, p. 323.
  • DR Oliver: Life history of Chironomidae. In: Ann Rev Ent. 16, 1971, pp. 211-230.
  • LCV Pinder: Biology of freshwater Chironomidae. In: Ann Rev Entomol. 31, 1986, pp. 1-23.
  • R. Schwind: Reflection polarization: A signal to recognize the habitat for hydrophilic insects. In: Negotiations of the German Zoological Society 85.1, 1992, p. 42.
  • C. Wesenberg-Lund : Biology of freshwater insects. Berlin 1943.
  • W. Wichard, W. Arens, G. Eisenbeis: Atlas for the biology of water insects. Stuttgart 1994.
  • F. Lenz: Flight of swallows, mosquitoes and weather. In: microcosm. 43rd year / 5, 1954, pp. 97-99.
  • R. Röhrig, HJ Beug, R. Trettin, P. Morgenstern: Subfossil chironomid assemblages as paleoenvironmental indicators in Lake Faulersee (Germany). In: Studia quaternaria. 21, 2004, pp. 117-112.

Web links

Commons : Chironomidae  - Collection of images, videos and audio files