See also: Fly

The éphéméroptères ( Ephemeroptera ) are one of Insecte S (of the Ptérygote S, section of the Paléoptère S).
the éphéméroptères appeared with the Carbonifère, there are approximately 280 to 350 million years. In fact the oldest winged insects of planet survive still today. One regards these insects with the soft teguments and the poor flight as insects in primitive matters. The fact of not being able to fold back their wings on their body in is an example (Paléoptère S).

Characteristics:

  • size: 3 to 40 mm (without the Cerque S)
  • wings finely ribbed and rigid, tended to the vertical at rest (not being able to fold up itself behind at rest), with absence of posterior wings at certain species). The wings are transparent and sometimes yellowish or brownish, even brilliant. They are decorated of a spot on their front edge with the extremity of the wing (Pterostigma). The first pair of wing is longer in the males.
  • former wings never not recovering the posterior wings.
  • small antennas, composed of short and thick articles, prolonged by a fine silk.
  • crushing oral parts in the larvae (the adult is not nourished, being devoted only to the reproduction, around fresh water where one especially sees them in end according to midday. He dies quickly from where his name " transitory ".
  • two or three long cerques multiarticulés, with sometimes a long caudal filament enters the cerques ones.
  • development of the type Hémimétabole.

The males have the forefeet longer than those of the females, presenting forceps at the end of the abdomen.
Les Imago S (adults) has a short life, only devoted to the reproduction and do not nourish themselves.
Les larvae is watery. They live one, two or three years, and pass by an intermediate final stage the Subimago which resembles much at the adult stage, but lasts only a few days or a few hours.

Lifestyle

They are insects related to the clean water and oxygenated well, this why they are regarded as goods Bioindicateur S.
Les female lays at water surface. The larvae will live there from 1 to 3 years.

Distribution

They everywhere are found where fresh water and oxygenated is durably present. In the middle of the years 1980, one knew approximately 2000 species in the world, to 25% in North America (200 in Europe, 125 in Australia)

Threats

The transitory ones belong to the insects which strongly regressed since about fifty years, probably following degradation of the water quality and with the general pollution of the environment by the Pesticide S. Until the beginning of the 20th century, they were present everywhere in swarms of thousands of individuals near fresh water.

Classification

Commonly called transitory S, flies of May or baskets, one counts approximately 3  of it; 000 S (340 in Europe) gathered in the S following:

The transitory exchange of sex

A small parasitic worm, the nematode Gastromermis , makes change sex the transitory males which it infects. Even if the transformation is not complete, the victims have behaviors of females which lead them to simulate the laying in the river beds. It is the occasion for the nematode to leave its host to continue his life cycle. If the transitory male had not been transformed, it would never be turned over in water and the worm could not have survived. A discovery of the entomologist Sarah Vance, University Cornell in the United States.

More:

Vance, S.A., 1996. Morphological and behavioral sex reversal in mermithid- infected mayflies. Proceedings off the Royal Society off London Series B-Biological Sciences 263 : 907-912

External bonds

  • '' Ephemeroptera '' on ''' Benthos '''

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