Blue blowfly ( Calliphora spec.)
|Linnaeus , 1758|
The two-winged (Diptera) form an order of the insects within the new winged (Neoptera). The two-winged species include almost 160,000 species from 226 families , with around 9200 species to be found in Central Europe. They reach an average height between 0.8 and 23 millimeters. The largest known species is Gauromydas heros with a body length of around 60 millimeters and a wingspan of 100 millimeters.
Construction of the two-winged aircraft
Two-winged birds are characterized by the fact that only two of the four wings usually found in insects are designed as such. These are the front wings, the rear wings, on the other hand, are transformed into so-called swinging arches ( holders ). These are considerably shorter and consist of a stem and a terminal, club-shaped thickening. The holders move when flying and are used to stabilize the flight by detecting Coriolis forces during rotations. A reduction in the hind wings can also be found in some male scale insects, whereas in the fan-winged (Strepsiptera) the forewings are converted into such holders. The shape of the two-winged species is very different, here the very filigree mosquitoes (Nematocera) are classically contrasted with the more compactly built flies (Brachycera).
Head: eyes and mouthparts
The compound eyes of the two-winged flies are usually well developed and lie on both sides of the head, whereby they can also touch on the upper side or, as in the peti-eyed flies, are far apart. Between these there are usually three point eyes ( ocelles ) in the forehead area . In the Schizophora there is also a very noticeable, horseshoe-shaped suture, known as the ptilinal suture . At this point, the flies that hatch from the pupa form a large bubble in the head to break off the pupal seam, which later disappears. Other head sections can also be particularly emphasized in individual groups, such as a crescent-shaped lunula above the antennae in the case of the hatchers (Cyclorrapha) or a conspicuous oculus triangle. The antennae have two basic members and in the mosquitoes carry a long, multi -jointed flagellum while in the flies this is transformed into a jointed remnant of the flagellum, usually consisting of only one to three segments. The bristling of the head (and other parts of the body) is also important for the identification and systematic classification of the animals. Here it is primarily the post-vertical bristles protruding from the vertex, the bristles on the eyes (orbital bristles and ocellar bristles) and the vibrissae or gag bristles on the mouth.
The mouthparts of the adults are either licking and sucking, as is the case with many types of flies, or stinging and sucking as with many types of mosquito. In a number of species, however, they are also completely regressed, so that feeding as an imago is not possible. The licking-sucking “lick-mouth trunk” of some flies consists of the pillow-like enlarged labial probes that form a closed channel through which liquids are sucked up. In many mosquito species, the mandibles and maxillae in particular are transformed into stinging bristles, and a saliva canal and a suction tube for ingesting food are also formed here.
Chest and limbs
The chest section ( thorax ) supports the legs as well as the wings and brackets. A large back plate, the mesonotum , can be seen on the upper side, which is adjoined by a smaller scutellum . A conspicuous transverse seam or, as in the case of the Schnaken (Tipulidae), a V-shaped seam can run on the mesonotum . On the sides of the thorax, the front humeri , which act like “shoulder pieces”, are particularly easy to recognize. This is followed by five side plates, which are called the pleuron. Two openings in the tracheal system ( spiracles ) open into the thorax, one in front of the mesopleurum and another directly in front of the holders in the hypopleurum. As with the head, in addition to the shape of the pleuras, various groups of bristles provide information on the species and system.
Like all insect legs, the legs are made up of a hip area ( coxa ), a thigh ring ( trochanter ), a femur , a tibia and a multi-part tarsus . On the last parts of the tarsus, especially in flies, there are so-called pulvillae and empodia . The empodium arises between the two claws and can also be claw-like or cushion-like. The pulvillae are adhesive flaps below the claws. Adhesion is made possible by excreted secretions and very fine hairs that arise from the pulvilla; in blowflies this is around 5000 hairs.
The wings are usually crystal clear and have clearly visible and specific wing veins . The arrangement of these veins and the field formation is a very important feature for determination and classification. In a few species, the wings can also be primary or secondary missing. The wing veins of the Diptera served the founder of the phylogenetic system , Willi Hennig , as an important working basis for his studies.
The abdomen, called the abdomen , consists of ten segments in the original species, which have been reduced to five to six in some taxa . The segments consist of clearly recognizable back and abdominal plates ( tergites and sternites ) with side plates ( pleurites ) and intersegmental membranes that are difficult to recognize . In most species there is a pair of stigmas of the tracheal system in each abdominal segment laterally on the edges of the tergites or between tergites and sternites. The rear end of the abdomen carries the sex organs, which in some species can be very prominent on the outside. In many males there is a hypopyg , which in addition to the actual mating organ (aedeagus) provides other auxiliary organs (e.g. holding forceps). The females have a sperm library for storing the sperm and not infrequently a laying tube ( ovipositor ), which can provide information about the potential oviposition location from its external nature.
Reproduction and development
Gender finding and mating
With the exception of the hermaphroditic representatives of the genus Termitoxenia , two- winged birds are bisexual. Optical and olfactory signals, but sometimes also acoustic signals, play a role in gender identification.
In many species there is a spatial or temporal coordination that makes it easier to find the sexual partner. The males of many coprophagous species wait for the females in the area of the oviposition sites on dung heaps. Pharynx collect on specific landmarks, mostly over mountain tops, and the closely related gastric brakes meet on rock faces. The fungus gnats are already forming as larvae a traveling chain of several meters length as armyworm is known and probably finding suitable Verpuppungsorte serves at which can also select the gender again after hatching. Temporal coordination can be found, for example, with the sea-living mosquitoes of the genus Clunio , which swarm in the evening hours only at the full moon and at the new moon .
With a great number of mosquito species and also with dance flies , large swarms of males form, which are optically visible from afar to females and which they can head towards. Within these swarms, the females are recognized by the males and taken to mate. The courtship behavior of the male stilt flies , which perform rhythmic movements with their legs or the spreading of the wings in some long-legged flies, is also visually recognizable . Commercial flights also occur with many types of flies.
In the case of mosquitoes , the females are attracted by the noise of the flight of the males, something similar also occurs with tufted midges and midges . Chemical attractants, so-called pheromones, have been found primarily in butterfly mosquitoes and fruit flies .
Mating takes place differently depending on the species and can take a few minutes to several hours. It partly takes place in flight, but mostly on the ground, in vegetation or on other suitable structures. The exchange of sperm always takes place through copulation , in which the male mating organs are led to the female sexual opening and penetrate it.
The eggs are usually laid shortly after mating in a substrate suitable for larval development. In the nasal dassels , the eggs develop in the female's body until they hatch and are only "shot" shortly before under pressure into the nostrils of suitable hosts . The time it takes for the larvae to hatch depends on the species and can range from a few hours to several weeks.
The primary larvae are legless and without a head capsule ( maggots ), as in flies or with a head capsule and stubby legs in mosquitoes. There are no real limbs in the larvae of the two-winged birds. In many mosquitoes, the larvae are adapted to life in the water and have external mouthparts that are designed like pots and breathing tubes. Otherwise, both the larvae and the adult animals have populated almost every habitat and there are all forms of life among them, from flower visitors to hunters to purely parasitic animals.
Two-winged insects belong to those insects with complete metamorphosis, so they are holometabolic . They pupate after the last of the three to four larval stages . In the moderate latitudes in particular, overwintering can take place as a larva or as a pupa. The finished insect, the imago , hatches from the pupa .
Some species of the two-winged species have a form of asexual reproduction called parthenogenesis . The paedogenesis in which an asexual reproduction is laid already in a larval stage comes before. The larvae of various gall midges of the genera Miastor and Heteropeza each produce new generations of gall midges, which, like them, also live under bark. The winged adults only develop in unfavorable living conditions, such as the habitat drying out . The fungus-dwelling gall mosquito Henria psalliotae forms successor generations in the pupa, here too no adults are developed.
Significance in human and animal hygiene
In human and animal hygiene , some two-winged species are of particular importance as pests , parasites and carriers of diseases. For this reason, various measures to protect insects have been developed.
Systematics of the Zweiflügler
The two-winged animals represent a very large group of animals, and the systematics of these animals is correspondingly extensive. Since the animals are relatively rich in features for differentiation and thus also for the reconstruction of the natural relationships (see Willi Hennig ), the systematic and phylogenetic representation is still a highly topical research area.
Commonly the two-winged species are divided into the two sub-orders mosquitoes (Nematocera) and flies (Brachycera). The mosquitoes, however, are very likely not a natural group ( monophylum ), but a combination of several lines of development with a similar habitus . The " Nematocera " form a paraphylum to the Monophylum Brachycera . The representation under the two-winged systematics shows the most important families, in which the two-winged Central Europeans in particular are classified.
The oldest known fossils of this order were found in a sub-Triassic formation in France. The fossils belong to the extinct suborder Archidiptera and the suborder Nematocera (mosquitoes). The oldest evidence of the subordination of the Brachycera (flies) comes from layers of the German Jura . Further Mesozoic forms (Cyclorrapha) were found in the Cretaceous Lebanon amber and in the somewhat younger Canadian amber (family Bibionidae ). The Mesozoic forms, which are well documented, largely lack highly specialized species. In tertiary amber deposits, especially in the Eocene Baltic amber , dipteras are among the most common organic inclusions and are represented in a correspondingly rich manner.
- Pape T., V. & Blagoderov Mostovski MB 2011: Order Diptera Linnaeus, 1758. In: Zhang, Z.-q. (Ed.) Animal biodiversity: An outline of higher-level classification and survey of taxonomic richness. Zootaxa 3148: 222-229, http://www.mapress.com/zootaxa/2011/f/zt03148p229.pdf
- RA Crowson et al. a. in: W. B. Harland u. a. (Ed.): The Fossil Record. Geological Society, London 1967, pp. 499-534, cited in George O. Poinar: Life in Amber. Stanford University Press, Stanford 1992, ISBN 0-8047-2001-0 .
- Müller: Textbook of Palaeozoology. Volume II, part 3, Jena 1978.
- George O. Poinar: Life in Amber. Stanford University Press, Stanford 1992, ISBN 0-8047-2001-0 .
- Wolfgang Weitschat, Wilfried Wichard: Atlas of plants and animals in the Baltic amber. Pfeil, Munich 1998, ISBN 3-931516-45-8 .
- Joachim Haupt, Hiroko Haupt: Flies and Mosquitoes. Observation, way of life. Naturbuch, Augsburg 1998, ISBN 3-89440-278-4 .
- Erwin Lindner: manual. Schweizerbart, Stuttgart 1949 ( The flies of the Palearctic region. Volume 1).
- Harold Oldroyd: The Natural History of Flies. Weidenfeld & Nicolson, London 1964.
- H. Schumann, R. Bährmann, A. Stark (eds.): Checklist of Diptera Germany. Ampyx, Halle 1999, ISBN 3-932795-01-6 .
- Diptera working group , independent interest group of dipterologists in Germany.
- diptera.info : interactive site for dipterists from all continents dealing with all aspects of dipterology.
- The Diptera Site - A community driven site for authoritative information on Diptera.
- Nature walk, by Andreas Haselböck. Overview of the Diptera species portraits
- Systema Dipterorum - Biosystematic Database of World Diptera.