www.kleine-wesen.org
www.kleine-wesen.org
A dragonfly is a flying insect belonging to the infraorder Anisoptera below the order Odonata. About 3,000 extant species of true dragonflies are known. Most are tropical, with fewer species in temperate regions. Loss of wetland habitat threatens dragonfly populations around the world. Adult dragonflies are characterized by a pair of large, multifaceted, compound eyes, two pairs of strong, transparent wings, sometimes with coloured patches, and an elongated body. Many dragonflies have brilliant iridescent or metallic colours produced by structural coloration, making them conspicuous in flight. An adult dragonfly’s compound eyes have nearly 24,000 ommatidia each. Dragonflies can be mistaken for the closely related damselflies, which make up the other odonatan infraorder (Zygoptera) and are similar in body plan, though usually lighter in build; however, the wings of most dragonflies are held flat and away from the body, while damselflies hold their wings folded at rest, along or above the abdomen. Dragonflies are agile fliers, while damselflies have a weaker, fluttery flight. Dragonflies are predatory insects, both in their aquatic nymphal stage (also known as “naiads”) and as adults. In some species, the nymphal stage lasts up to five years, and the adult stage may be as long as 10 weeks, but most species have an adult lifespan in the order of five weeks or less, and some survive for only a few days. They are fast, agile fliers capable of highly accurate aerial ambush, sometimes migrating across oceans, and often live near water. They have a uniquely complex mode of reproduction involving indirect insemination, delayed fertilization, and sperm competition. During mating, the male grasps the female at the back of the head, and the female curls her abdomen under her body to pick up sperm from the male’s secondary genitalia at the front of his abdomen, forming the “heart” or “wheel” posture. Dragonflies make use of motion camouflage when attacking prey or rivals. Fossils of very large dragonfly-like insects, sometimes called griffinflies, are found from 325 million years ago (Mya) in Upper Carboniferous rocks; these had wingspans up to about 750 mm (30 in), though they were only distant relatives, not true dragonflies. Dragonflies are represented in human culture on artefacts such as pottery, rock paintings, statues, and Art Nouveau jewellery. They are used in traditional medicine in Japan and China, and caught for food in Indonesia. They are symbols of courage, strength, and happiness in Japan, but seen as sinister in European folklore. Their bright colours and agile flight are admired in the poetry of Lord Tennyson and the prose of H. E. Bates.
Dragonflies, belonging to the infraorder Anisoptera, have hindwings that are broader than their forewings. They are similar in structure to a group called the griffinflies, which include the largest insect that ever lived. There are about 3,012 known species of dragonflies, spread across every continent except Antarctica. Dragonflies are heavy-bodied insects with horizontal wings and have distinctive characteristics such as large compound eyes, strong wing muscles, and a long abdomen. They are preyed upon by birds, wasps, frogs, fish, and water spiders, and can also be affected by parasites like water mites, gregarine protozoa, and trematode flatworms.
Die Großlibellen (Anisoptera) sind eine Unterordnung der Libellen und umfassen weltweit etwa 2800 Arten, die in elf Familien untergliedert werden. In Deutschland sind 51 Arten der Großlibellen verbreitet.
Großlibellen, auch bekannt als Libellen, gehören zur Ordnung der Odonata. Sie sind größer und kräftiger gebaut als kleinere Libellenarten und haben größere Facettenaugen, die oft in der Kopfmitte zusammenstoßen. Ihre Flügel sind breiter als bei anderen Libellenarten und können teilweise bunt getönt oder dunkel gefleckt sein. Großlibellen sind sehr geschickte Flieger und können auch lange Strecken zurücklegen. Die Larven der Großlibellen leben räuberisch im Wasser und können sich durch Ausstoßen von Wasser fortbewegen. Großlibellen werden in verschiedene Überfamilien und Familien unterteilt und sind Namensgeber des DragonFly BSD Betriebssystems.