Stenus
Stenus biguttatus
The genus Stenus Latreille 1779 belongs to the family of rove beetles ( Staphylinidae ) and, with 2,246 worldwide extant species one of the most species-rich genera of the entire animal world while Europe there are 309 species and subspecies distributed, 120 of them in Central Europe.
- 5.1 Notes and references
- 5.2 Literature
Features
The beetles reach a body length of 1.7 to 7.5 millimeters and have a typical Staphylinidenhabitus on. Their compound eyes are very large, are easily visible and occupy the entire side of the head. The elongated, dark-colored body is often strong and dense point-like structure. The sensors are turned in at the end freely between the compound eyes. The temples are not clearly developed. The head is inclusive of the eyes usually wider than the pronotum. This is tapered rear neck -like. The tarsi are five-membered. The Analsegment missing the two long bristles, there are at most short cilia formed. The individual species look very similar and are difficult to distinguish from each other. A unique species identification of the beetle is often only possible by the preparation of the male genital tract.
Occurrence and life
The way of life of the animals has a large bandwidth. There are species that live on the margins of rivers and lakes or in marshy habitats, others can be found in the litter layer in forests, in Genist, on the edge of snow fields, in heathen or in ant nests. The animals are predators and feed on Collembola and small insects. To grip the prey the labium provided with adhesive pads can be quickly thrown forward on the prey animal and then drawn with this again.
Chemical Ecology
Chemical Defence
To protect the exposed, not covered by elytra abdomen from attacks by predators and the colonization by microorganisms, have the members of the genus Stenus on potent chemical defense substances ( terpenes, pyridines, Piperidinalkaloide ). These are produced in paired Pygidial Glands at the abdomen tip, taken with the hind legs and spread through intense brushing on the body surface. Thus, the complete animal is impregnated with the defense substances. If the beetle is attacked, he can also evaginate a part of the defense glands of the Abdominalspitze and apply by curving the abdomen the defense secretions directly at the attacker.
Spreitungsschwimmen
In addition to the repellent effect the Pygidialdrüsensekret can also be used for locomotion on the water surface. The so-called Spreitungsschwimmen the beetles are on the water surface standing from a small drop of his glandular secretion. This is distributed at very high speed on the water surface and forms a thin film of secretion, at the edge of a piece of beetle is carried away. If the secretion delivery process, the animal at a rate of up to 75 cm per second can slide over the surface without moving the legs. By curvature of the abdomen, the movement direction can be actively controlled.
The phenomenon of Spreitungsschwimmens has hitherto observed only in Stenus and some representatives of the genus Velia bugs. However, the latter do not use Pygidialdrüsensekret but salivary substances for locomotion on the water surface.
Types (selection)
- Common Schmalkurzflügler ( Stenus clavicornis )
- Stenus comma
- Stenus bipunctatus
- Stenus longipes
- Stenus guttula
- Stenus maculiger
- Stenus fossulatus
- Stenus boops