Nemouridae

Nemoura cinerea

The Nemouridae are the most species-rich family of stoneflies. It includes nearly 400 species in 17 genera. The Nemouridae are spread across the entire Northern Hemisphere ( Holarctic ), in the southern hemisphere they are replaced by the similar family Notonemouridae. The family is divided into subfamilies Nemourinae and Amphinemurinae. Important, also in Europe, species-rich genera are represented eg Nemoura, Protonemura, Amphinemura, all these genera are common with nearly 100 species worldwide. As other European genus Nemurella is common with the only kind Nemurella picteti far.

Features

Nemouridae are relatively small, usually lacking in contrast and dark -colored stone flies, the abdomen is often reddish brown. The wings are often clouded dark, sometimes spotted, and laid flat at rest above the other worn on the abdomen. The most striking feature of the family is a special structure of the Flügelgeäders: Through an oblique cross- vein at the wing leading edge gives a distinctive X-shaped structure on the forewing. However, this feature is not entirely reliable, because it occasionally occurs even with representatives of other families. The Nemouridae have short, only monomial Cerci that train never long tail filaments. In the males, they are a part of the complicated Begattungsapparates, which occupies the entire rear end and usually form its special structures the only feature for secure species identification; many females are therefore not determined to species level.

At the head of the last segment of the labial is extended to a flat, round structure. The mandibles and maxillae are relatively wide, they serve the animals for food production, which is carried out by scraping plant matter, mostly algae or partially decomposed detritus. The three segments of the thorax are approximately equal, the prothorax is rectangular and filled up by hair and short Dörnchen. The second Tarsalsegment the legs is always significantly shorter than the first. The abdominal end of the male carries complicated built copulatory organs. In the female the abdominal plate ( sternite ) of the seventh segment is usually extended to the rear and forms a subgenital.

The adults of most species are capable of flight, but little active flight and usually found near the Larvalgewässer. In case of failure, they often let go and try rather to dive in crop maze than fly away. The North American genus Nanonemoura is wingless.

Larvae

The larvae of Nemouridae similar in body shape very the Imagines, missing only that wing and copulatory organs, and ( Cerci the ) sit on the abdomen end up getting two elongated tail threads. In the neck region ( Cervikalregion ) behind the head sitting in some genera distinctive tube ( eg Protonemura ) or tufted (eg Amphinemura ) gills, which are very characteristic for each genus. The gills are still recognizable in the rule to the Imagines as shrunken gill rudiments. The wing buds of the larvae are formed as a rigid wing sheaths that extend generally in all types of family in characteristic form obliquely backwards. The body seems relatively stocky, not as elongated as that of the related families Leuctridae and Capniidae. At the whole body, but especially on the femora of the legs usually sit strong, spine -like bristles, but may be absent.

Ecology and life

Nemouridenlarven are typical inhabitants of cold, clear streams ( Rhithral ) and sources ( Krenal ). In rivers ( potamal ) they are missing, however, largely. Only a few genera and species live in stagnant waters, including the Ubiquist Nemoura cinerea, which can colonize more polluted waters as one of the few species of stoneflies. Colonized particularly rich in species are mountain streams, in which may occur next to each other without further thirty species, but these are in the larval stage so similar that they can not be determined. Many species are endemic species of mountain ranges, such as seven species in the Alps and fifteen in the Pyrenees. The lowland regions generally have not only species occuring.

Nemouridenlarven live on the stream bottom, on gravel or stones or fall foliage. Only a few species are more common on soft substrates such as sand or water plants. Most species grate organic matter such as fallen leaves from ( " shredder " ), or they collect finer particles on the ground, a few graze ( biofilm ) from algae and micro-organisms on the surface of stones from.

The larval development of Nemouriden usually lasts one year ( monovoltin ). In the far north, some species take two years ( semivoltin ).

Fossils

Animals with the features of the recent family, but some plesiomorphies such as tripartite Cerci, are in excellent preservation from Siberia and from Inner Mongolia (China) ago. For them, a family Protonemouridae was (not to be confused with Protonemurinae without o! ) Erected, which should form the core group of Nemouridae and Notonemouridae. There are both fossil imagines as well as larvae Recent forms be similar in most characteristics. The development branch of the family is thus at the age safely Mesozoic, probably Jurassic.