The Plécoptères or pearls are one of Insecte S, of the Ptérygote S, superorder of the Orthoptéroidé S, winged, with the soft and lengthened body.
C' is an old group, which one finds fossils dating at least from the beginning of the Carboniferous one. On a world level, more than 2000 S of Plécoptères are currently indexed, measuring few millimetres to 5 cm for largest. North America counts approximately 4 times of them more species than Europe.

They are generally pledged with the Wetlands at fort running (waters running). They fly only at short distances, near the Berge S, Torrent S, Fossé S and Ripisylve S. They rest readily on stones and branches emerging of water or in the vicinity. Sometimes one finds them in great number near water, posed on the stones fraiches of arches and piles of bridges, with the entries of caves, on walls of pits.).
Cet order gathers plant species, omnivores/détritivores and carnivores.

They have a development of the type Hémimétabole (incomplete metamorphosis).

Larva S and nymphs (immature individuals)

They live all in the River, whereas the adults (or Imago S) are air.
Commes the larvae of Transitory S, the body of the larvae of Plécoptères is equipped with gills and is adapted to the current (flattened dorso-ventralement, legs laid out along the body, and not on the lower part). This form offers less resistance to the current, enabling them to live near the bottom of the bed, on or under the stones, where the current is the least important.

The larvae of Plécoptères are also used like Bioindicateur, because very sensitive to the oxygen rate dissolved in water. For example, a pollution by waste water rejection in the rivers will cause a brutal reduction in certain families of Plécoptères like the Perlidae. They are regarded as indicating groups in tests of water quality like the total biological Indice standardized (I.B.G.N.).

Characteristics

• a pair of antennas long, solid and multiarticulées
• two Cerque S, sometimes as long as the body
• two eyes, and three Ocelle S
• two pairs of almost transparent wings, with venous network very marked
• at rest, the wings are folded up flat on the back. The former wings are simple and oval, less broad than the posterior ones.
• the males of many species have the atrophied wings, and
• the legs all of the same type cannot thus steal, are teminées by a tarsus in three articles
• the Larve S are deprived of Branchies, oxygen diffusing through the body, incidentally using small tufts of hairs
• all the larvae begin their development with a mode brouteur-scraper of biofilm and algae. Then, while growing some acquire a mode détrivore and nourissent in particular litters resulting from the vegetation of the banks of the rivers. Other families, in particular those resulting from the species of big size, become only predatory thereafter.
• the moults of the larval cycle generally follow one another over a one year duration, but three years for certain species

The determination of the ous-orders, kinds and species generally require the observation of the bodies copulateurs. For this reason, the naturalists preserve them in Alcohol when that is necessary.

Food

The adult manqe of the algae, fragments of lichens or pollens. Certain species seem not to be nourished, devoting their short life of adult to the reproduction. The females generally live 2 to 3 weeks, and the males one week less.

Reproduction

At male and female springs couple themselves. The female immerses its eggs agglomerated in small packages in a well oxygenated water. The larvae develop in water during at several years, with a cycle from 20 to 30 moults before final stage which will be air.

Threats

In fact species often tend to regress and which locally disappeared, because probably of the increasing pollution of the rivers. Certain species seem not to fly at long distances, which does not facilitate the recolonisation of a medium after a Pollution, especially when their biological Corridors disappeared.

Families

In the order of the plécoptères , one finds in Europe the following families:

• Taeniopterygidae
• Nemouridae
• Capniidae
• Leuctridae
• Pteronarcyidae
• Styloperlidae
• Peltoperlidae
• Perlodidae
• Perlidae
• Chloroperlidae

Images

Random links:

Corcelles-on-Chavornay | Inverness (Scotland) | Routh torch | Stalemate Woodell | Doctor fireman