Stenus

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Stenus
Biguttatus stenus

Biguttatus stenus

Systematics
Class : Insects (Insecta)
Order : Beetle (Coleoptera)
Subordination : Polyphaga
Family : Kurzflügler (Staphylinidae)
Subfamily : Steninae
Genre : Stenus
Scientific name
Stenus
Latreille , 1797

The genus Stenus belongs to the short-winged family (Staphylinidae) and, with over 2,700 recent species worldwide, is one of the most species-rich species in the entire animal world. In Europe, 309 species and subspecies are distributed, 120 of them in Central Europe.

features

Stenus impressus

The beetles reach a body length of 1.7 to 7.5 millimeters and have a typical Staphyliniden habitus . Her compound eyes are very large, stand out clearly and take up the entire sides of the head. The elongated, dark-colored body is often strongly and densely structured in punctiform fashion. The antennae are freely positioned between the compound eyes on the forehead. The temples are not clearly formed. The head, including the eyes, is usually wider than the pronotum . This is neck-like at the back. The tarsi are five-part. The anal segment lacks the two long bristle hairs, at most short eyelash hairs are formed. The individual species look very similar to one another and are difficult to distinguish from one another. An unambiguous identification of the species of the beetle is often only possible by dissecting the male genital apparatus.

Occurrence and way of life

The way of life of the animals shows a wide range. There are species that live on the edge of water or in swampy habitats, others can be found in the litter layer in forests, in genist, on the edge of snow fields, in heaths or in ant nests. The animals are predatory and feed on collembola and other small insects. To grip the spoil the provided with adhesive pads may Labium very quickly after thrown forward in the prey animal and are then fed again with this.

Chemical ecology

Chemical defense

In order to protect the exposed abdomen , which is not covered by elytra , from attacks by predators and colonization by microorganisms, the representatives of the genus Stenus have potent chemical defense substances ( terpenes , pyridines , piperidine alkaloids ). These are produced in paired pygidial glands on the tip of the abdomen, picked up with the hind legs and distributed on the surface of the body through intensive cleaning. As a result, the entire animal is impregnated with the defense substances. If the beetle is attacked, it can also protrude part of the defense glands at the abdominal tip and, by bending the abdomen, apply the defense secretions directly to the attacker.

Spread swimming

In addition to the defense effect, the pygidial gland secretion can also be used to move on the surface of the water. During the so-called spreading swim, the beetle releases a small drop of its glandular secretion while standing on the surface of the water. This spreads over the surface of the water at a very high speed, where it forms a thin film of secretion, along the edge of which the beetle is carried away a little. If the secretion is released continuously, the animal can glide over the surface of the water at a speed of up to 75 cm per second without moving its legs. The direction of movement can be actively controlled by curving the abdomen.

The phenomenon of spreading swimming has so far only been observed in Stenus and some members of the Velia genus . The latter, however, do not use pygidial gland secretions, but salivary gland constituents for movement on the water surface.

Types (selection)

swell

Individual evidence

  1. ↑ THAYER KK (2005) July 11. Staphylinidae Latreille, 1802. In: Kristensen NP & Beutel RG (editor), Handbuch der Zoologie IV, Arthropoda: Insecta, Volume 38, de Gruyter Verlag, Berlin-New York.
  2. ↑ Stenus. Fauna Europaea, accessed May 3, 2010 .
  3. ↑ a b BETZ O. (1999) A behavioral inventory of adult Stenus species (Coleoptera: Staphylinidae). Journal of Natural History 33: 1691-1712.
  4. ↑ a b LINSENMAIER KE, JANDER R. (1963) The "relaxation swimming" by Velia and Stenus . The Natural Sciences 50 (6): 231

literature

  • Karl Wilhelm Harde, Frantisek Severa and Edwin Möhn: The Kosmos Käferführer: The Central European Beetles. Franckh-Kosmos Verlags-GmbH & Co KG, Stuttgart 2000, ISBN 3-440-06959-1 .
  • A. Horion: Faunistics of the Central European Beetles Volume IX: Staphylinidae 1st part: Micropeplinae to Euaesthetinae, Ph.CW Schmidt publishing house, Neustadt ad Aisch, 1963.
  • Edmund Reitter: Fauna Germanica - The beetles of the German Empire. 5 volumes, Stuttgart KG Lutz 1908–1916, digital library volume 134, Directmedia Publishing GmbH, Berlin 2006, ISBN 3-898-53534-7 .