Scirtidae

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Scirtidae
Cyphon laevipennis

Cyphon laevipennis

Systematics
Class : Insects (Insecta)
Order : Beetle (Coleoptera)
Subordination : Polyphaga
Partial order : Elateriformia
Superfamily : Scirtoidea
Family : Scirtidae
Scientific name
Scirtidae
Fleming , 1821

The Scirtidae are a family of beetles within the superfamily Scirtoidea . The family does not have a common German name, names that are occasionally used are swamp beetles, sump fever beetles, yoke beetles or mud beetles. The family, which is widespread worldwide, includes around 1300 species, although the fauna of numerous regions has so far hardly been explored. In Central Europe, 26 species in 8 genera are known.

features

They are relatively small beetles, 1.5 to 12 millimeters long, with a more or less elongated, oval, closed body contour and usually fine hair. They are usually delicate and relatively soft sclerotized and inconspicuously dark, brownish or yellowish in color, without any distinctive markings. The head , which is usually inclined slightly downwards, has eleven-link antennae , the antennae links are widened in some genera (sawn or combed antennae). The eyes are usually relatively large and protrude from the contour of the head. The pronotum is usually shorter than it is wide. The elytra are smooth without rows or stripes of dots and completely cover the abdomen. Five sternites are visible on the ventral side . The tarsi of the legs are five-limbed, usually the fourth limb is noticeably enlarged and often bilobed. Some genera with enlarged thighs ( femora ) and noticeably elongated tibial spurs have jumping ability (e.g. genus Scirtes ).

Larvae

The larvae are elongated, with either parallel-sided or leaf-shaped extended body segments ("slice-shaped" body contour). As a rule, the surface of the body is clearly sclerotized on both the upper and the lower side and is darkly colored or marked. The large head is stretched forward. The long, uniformly curled antennae with numerous antenna elements are remarkable, correspondingly long antennae are otherwise not found in beetle larvae. Strikingly, the number of antenna elements is not constant, but increases with each of the five larval stages. Apart from the size, the larval stages show hardly any differences. The head has otherwise greatly enlarged and densely haired maxillae to sweep food particles together and convey them to the mouth. They are swung outwards in a regular movement and then caught again. The hypopharynx also carries filter bristles that help remove excess water.

The rest of the body is relatively uniformly structured, the pronotum barely longer than the following trunk segments. The three pairs of legs are relatively long. The abdomen has eight or nine free, recognizable segments. At the end of the abdomen there is usually an enlarged breathing chamber, which is formed from the tergites eight and nine and contains a pair of enlarged spiracles . The larvae are air breathers and have to come to the surface of the water regularly to absorb oxygen.

Way of life

In all Scirtidae the larvae are aquatic, the adults land-living, mostly in the vicinity of water. Only a few non-European genera live as larvae, exceptionally, in water-saturated soil or wet dead wood. The larvae colonize a variety of different types of water, from springs and streams to ponds and lakes. In spring runoffs and forest streams in particular, they can reach very high densities and are among the most common types of macrozoobenthos . Since they are air breathers, they avoid deep water bodies and very large bodies of water. All larvae live on the ground and have no swimming ability. The larvae of some species have occasionally been observed in the groundwater, but, as far as is known, no specialized species exist. Many species are specialists in water retention in plant cavities, e.g. B. in the leaf axils of bromeliads ( phytotelms ). The larva of the Central European Prionocyphon serricornis lives z. B. exclusively in the accumulations of water in knotholes and root niches of old deciduous trees. The larvae of the Central European species can be found mainly in clusters of fallen leaves on the bottom of the water (the flattened species), or in the system of gaps in the river bed, the interstitial (the elongated species). They usually live hidden (negative phototactic ). All species feed on fine organic matter ( detritus ). Almost nothing is known about the food intake of adults.

Life cycle

The Central European species usually have one generation per year (univoltin). Larval as well as imaginal hibernators occur. In larval hibernators, the second or third larval stage overwinters, pupation takes place in August of the following year. The larvae ready to pupate leave the water, mostly they dig a cave in the ground as a pupa cradle in the immediate vicinity of the bank, they pupate without a shell or web. In some species pupation takes place in the water as an exception. The pupa rest is very short (2 to 4 days), and the lifespan of the adults is very short in larval overwinterers.

Systematics

Together with the families Clambidae , Decliniidae and Eucinetidae , the Scirtidae form the superfamily Scirtoidea. The position of the scirtoid is very controversial. The traditional classification in the suborder Elateriformia , mostly as a sister group of the Dascilloidea , is supported by most of the authors on the basis of the morphology. However, the family has numerous original (plesiomorphic) features. In molecular studies (based on homologous DNA sequences) there was often a very basal position of the Scirtoidea, which would therefore be the most original Polyphaga and sister group of all others. A similar position had already been considered on a morphological basis (veins of the hind wings), but is rejected by most systematists.

Three subfamilies are recognized within the Scirtidae.

selection

Scientific synonyms for Scirtidae are Helodidae, Elodidae and Cyphonidae.

swell

Web links

Commons : Scirtidae  - Collection of images, videos and audio files

Individual evidence

  1. ^ A b c Bernhard Klausnitzer (2008): Brief presentation of the Scirtidae family (Coleoptera) (137th contribution to the knowledge of the Scirtidae). Entomologica Austriaca 15: 33-40.
  2. ^ A b John F. Lawrence: 15.4 Scirtidae, Fleming, 1821. In: Rolf G. Beutel & Richard A. Leschen (editor) Handbook of zoology. Volume IV. Arthropoda: Insecta. Part 38. Coleoptera. Volume 1: Morphology and systematics, Archostemata, Adephaga, Myxophaga, Polyphaga partim. Berlin, New York: Walter de Gruyter. pp. 443 ff.
  3. ↑ cf. Cladogram in Toby Hunt, Johannes Bergsten, Zuzana Levkanicova, Anna Papadopoulou, Oliver St. John, Ruth Wild, Peter M. Hammond, Dirk Ahrens, Michael Balke, Michael S. Caterino, Jesús Gómez-Zurita, Ignacio Ribera, Timothy G. Barraclough , Milada Bocakova, Ladislav Bocak, Alfried P. Vogler (2007): A Comprehensive Phylogeny of Beetles Reveals the Evolutionary Origins of a Superradiation. Science 318: 1913-1916. doi : 10.1126 / science.1146954
  4. ^ H. Song, N. Sheffield, SL Cameron, KB Miller, MF Whiting (2010): When phylogenetic assumptions are violated: base compositional heterogeneity and among-site rate variation in beetle mitochondrial phylogenomics. Systematic Entomology Volume 35, Issue 3: 429-448. doi : 10.1111 / j.1365-3113.2009.00517.x
  5. ^ Tree of Life Web Project. 2011. Scirtidae. Marsh beetles. Version 15 February 2011 (under construction). [1]