Notonectidae
Common backstroke swimmer ( Notonecta glauca )
Backstroke ( Notonectidae ) are a family of aquatic insects living in the subordination of the bugs ( Heteroptera) in the partial order of the water bugs ( Nepomorpha ). Worldwide there are about 350 known species. The special characteristic of these animals is that they always swim with the ventral side up - and below the water surface. This striking swimming position resulting from the ventral to the abdomen entrained air supply. Since they can sting sensitive, back floats are also popularly known as " water bees".
- 3.1 Types in Europe
- 4.1 Literature
- 4.2 Internet Resources
Features
Rückenschwimmer reach body lengths of about 13.5 to 18 millimeters. The body top is curved boat-shaped. The belly is always flat. The air supply of bugs is located mainly on the ventral side. The positive buoyancy in the water, the bottom of the animals turns up. The head is broad and bears strikingly large eyes. The eyes are designed as so-called double eyes. The back side ( posterior ) and ventral ( ventral ) part is different in the number of facets and the pigmentation. The light-facing part is more organized and allows an accurate vision. The side facing away from the light is less specialized and is used with a wide horizon as the viewfinder. The short sensor (antenna ) of the back swimmer lie at the bottom of the head and rest on a bubble, which is located in a pit between the head and prothorax ( prothorax ). The second and third links are hairy. The third antennal segment has special sensory hairs. The coat prevents beading of the bubble. The neural pathways of the sensory hairs on the antennae mediate muscle movements that function together with the upwardly mobile air bubble as an equilibrium organ. The wings are designed to be very strong and completely despite their aquatic lifestyle. With enough warm weather they crawl ashore to dry their wings (which can take up to 15 minutes ) and fly, mainly to seek new water points. In this they throw themselves with wings closed. New water points only with the help of the eyes found, where they respond to very bright surfaces. Rückenschwimmer move with their powerful legs rudder just below the water surface bursts forth. The proboscis is kept short and strong.
Way of life
Rückenschwimmer live in pools, ponds and lake shores. Even in larger, deep puddles, the animals can exist. They are adapted to a particular way of life in the water. Notonectiden are skilful swimmer. They are capable by their laterally compressed body, to cut through the water. The rear pair of legs is the rudder body. The rail and the foot are covered with long stiff wettable (hydrophilic) bristle hair. When you check the legs, the bristles splay off and zoom out to the rudder area.
Breathing
For breathing pierces the back float with the abdomen tip in the supine position the water surface. The middle and front legs support from the animal, which is easier through the air reservoir as water against the surface tension of the water. The hind legs keep the balance. The abdomen tip protrudes from the water. This is surrounded by a non-wettable ( hydrophobic ) Hair Wreath and can thus break through the surface film. When sticking out of the abdomen fold on the ventral side on two tunnel -forming rows of bristles and take in air on. This close again when diving. These supply channels associated with cavities on the chest and under the wings in conjunction. Rückenschwimmer are formally surrounded by air spaces. At the bottom of these channels are Tracheenöffnungen, so that oxygen can be used from this pool for respiration, that is, in the tracheae can diffuse into it. This air supply buoyancy is so strong that they have to row while diving violently with his hind legs or hold on to the two front pairs of legs.
Nutrition
In the supine position, the animal remains under the surface, waiting for its prey to come either to breathe at the surface or swims within reach. Notonectiden can also absorb surface vibrations into the water fallen insects. The prey is grabbed and sucked sure with the middle and front legs. Almost all Rückenschwimmer are predators. They feed on all the insects they overwhelm you. Even small fish and tadpoles are eaten.
Outside Europe, there are species in the family of Notonectiden which feed on plankton. So Buenoa margaritacea is a plankton feeder. The bug sets the front and middle legs close to the body. The hair on the leg forms a kind of reuse, through which the water is filtered. This microorganisms stick to the bristles.
Reproduction and Development
The pairing of backstroke swimmer may take several hours. Therefore, they must assume a position in which they can breathe. They hang side by side on the water surface. The male is slightly below the female. Egg-laying is different species-specific. Notonecta glauca lowers their oblong- oval, about 2 mm long eggs by means of a short ovipositor into the plant tissue. Similarly, Notonecta obliqua and Notonecta lutea behave. Notonecta viridis cements her eggs occasionally, Notonecta maculata always on stones. The times of oviposition are different as species specific. In Notonecta glauca is the end of March the pair and soon after oviposition a. Notonecta viridis extends the oviposition until the autumn. Notonecta maculata begins only in the fall to lay eggs and continues with it even in warm winter months. This results in different forms of wintering the back float types as full as an egg or insect.
Rückenschwimmer are like hemimetabol all bugs. They go through five larval stages, which merge into each other over molts. The larvae are doing the adult animal gradually more and more similar.
Dissemination
Backstroke swimmer of the genus Notonecta are particularly widespread in the Neotropics and diverse. While in the south of the Old World species of the genus Anisops are numerous, there are in the New World species of the genus Buenoa.
Species in Europe
- Anisops crinitus Brooks, 1951
- Anisops debilis Gerstaecker, 1873
- Notonecta ( Notonecta ) canariensis Kirkaldy, 1897
- Common backstroke swimmer ( Notonecta ( Notonecta ) glauca ) Linnaeus, 1758
- Notonecta ( Notonecta ) lutea Müller, 1776
- Notonecta ( Notonecta ) maculata Fabricius, 1794
- Notonecta ( Notonecta ) meridionalis Poisson, 1926
- Notonecta ( Notonecta ) obliqua Thunberg, 1787
- Notonecta ( Notonecta ) pallidula Poisson, 1926
- Notonecta ( Notonecta ) reuteri Hungerford, 1928
- Notonecta ( Notonecta ) viridis Delcourt, 1909
- Nychia marshalli (Scott, 1872)