The name of the family to which they belong, ephemerid, suggests their ephemeral existence.
Those examples are provided by Rotifera (inferior worms) and by ephemerid.
They are like the ephemerid insects which live for a summer day only.
In the ephemerid they lie in planes approaching the vertical, slightly diverging from each other towards their extremities.
I do not propose in this work to deal with ephemerid, as the wings in the imitations now sold are in the natural position.