EPHEMERA. 
377 
of the animal, by a couple of small bladders, which 
it has the power of filling with air immediately after 
they are excluded, and thus restoring the equili- 
brium. 
There are several species of this genus, which are 
not easily distinguished from each other, especially 
the smaller kinds. Among them is one which 
greatly resembles the Ephemera vulgata , except in 
the colour, which is white : this is described by 
Swammerdam, and quoted as a remarkable instance 
of the shortness of animal life ; the insect assuming 
its winged state, fulfilling the purposes of its birth, 
and perishing, in the course of the same evening. 
The species mentioned by Reaumur may possibly 
be distinct from our English kind, as it appears at 
a different season, and has not so long a term al- 
lowed for its existence. 
