Scirtidae

Cyphon laevipennis

The Scirtidae are a family of beetles within the superfamily Scirtoidea. A widespread German name does not have the family name occasionally used are swamp beetles, malaria beetles, Jochkäfer or mud bugs. The world used family comprises about 1300 species, but the fauna of many regions has barely explored. In Central Europe, 26 species in 8 genera are known.

Features

It is relatively small beetle 1.5 to 12 millimeters in body length, with more or less elongated oval, closed, body outline and usually finer hair. They are delicate and usually relatively soft and inconspicuous sclerotized dark, brownish or yellowish, without striking drawing. The usually slightly downwardly inclined head carries eleven-membered antennas, the antenna elements are, for some species extended ( sawn or combed antennas). The eyes are usually relatively large and protrude from the head contour. The pronotum is shorter than usually wide. The elytra are smooth without rows of dots or dot strips and cover the abdomen completely. On the ventral side five sternites are visible. The tarsi of the legs are five-membered, usually the fourth link is conspicuously enlarged and often bilobed. Some genera with enlarged legs ( femurs ) and strikingly prolonged Tibienspornen own jumping ability (eg genus Scirtes ).

Larvae

The larvae are elongate, parallel-sided either with or on the sides of leaf-shaped extended body segments ( " assel shaped " body outline). The body surface is sclerotized usually evident both on the top and on the bottom and dark colored or drawn. The large head is protruded forward. The long, uniformly ringed antennae with numerous antenna elements are remarkable, according to long antennas are in beetle larvae otherwise not exist. The number of antenna elements is strikingly enough, not constant, but increases with each of the five larval instars. Otherwise, the larval stages, apart from the size, differed little. The head bears otherwise greatly enlarged and hairy maxillae to sweep up food particles and to transport it to the mouth opening. They are swinging on that in a regular motion to the outside and caught up. The hypopharynx also carries filter bristles that help to deposit excess water.

The rest of the body is divided relatively uniform, the pronotum ( pronotum ) is hardly longer than the following body segments. The three pairs of legs are relatively long. The abdomen has eight or nine free, identifiable segments. On abdome usually sits an enhanced respiratory chamber, which is formed from the tergites eight and nine and a pair of enlarged stigmas contains. The larvae are air-breathers and have regularly come to the oxygen intake to the water surface.

Way of life

For all Scirtidae the larvae are water alive, which imagines country living, usually near water. Only a few non-European species live as larvae in water-saturated soil or exceptionally drenched deadwood. The larvae inhabit a variety of different types of water, of springs and streams to ponds and lakes. Especially in spring runoff and forest streams they can reach very high densities and individuals are among the most common types of benthic invertebrates. Since they are air-breathers, but they avoid deep water bodies and very large bodies of water. All larvae are ground alive and have no buoyancy. The larvae of some species were occasionally observed in the groundwater, but there are, as far as known, no specialized species. Numerous species are specialists for water accumulations in cavities of plants, eg in the leaf axils of bromeliads family ( phytotelmata ). The larva of the Central European Prionocyphon serricornis lives eg exclusively in the accumulation of water in knots and root niches of old deciduous trees. The larvae of the Central European species are found mainly in accumulations of leaf litter on the seabed ( the flattened species), or in the pore system of the river bed, the interstitial ( the elongated species). They live mostly hidden (negative phototaxis ). All species feed on fine organic matter ( detritus ). About the food intake of imagos almost nothing is known.

Life cycle

The Central European species usually have one generation per year ( univoltine ). It can be found both larval as well Imaginalüberwinterer. The Larvalüberwinterern wintered the second or third instar larvae, which pupate in August of the following year. The verpuppungsbereiten larvae leave the water, usually they dig a hole in the ground close to the bank as Puppenwiege, they pupate without a cover or fantasy. In some species pupation takes place exceptionally well in the water. The pupal period is very short ( 2-4 days), the life of the imago is very short at the Larvalüberwinterern.

System

Together with the families Clambidae, Decliniidae and Eucinetidae form the Scirtidae the superfamily Scirtoidea. The position of the Scirtoidea is very controversial. The traditional classification in the subordination Elateriformia, usually as a sister group of the Dascilloidea is supported by most of the editors on the basis of morphology. However, the family has lots of original ( plesiomorphic ) characteristics. In molecular studies (due to homologous DNA sequences ) in many cases resulted in a very basal position of Scirtoidea question, is the most primitive Polyphaga, and sister group of all other would be. A similar position had already been considered on the basis of morphological ( venation of the hind wings ), but is rejected by most taxonomists.

Within the Scirtidae three subfamilies are recognized.

• Nipponocyphoninae (one species, Japan)
• Stenocyphoninae (one species, Chile)
• Scirtinae ( the remaining species )

Scientific synonyms for Scirtidae are Helodidae, Elodidae and Cyphonidae.

Swell

• G. A. Lohse (1979 ): 40 Family Helodidae. In H. Joy, K. W. Harde, G. A. Lohse (eds.). The beetles of Central Europe. Volume 6