SOS 
NATURAL HISTORY. 
aiul some cream-coloured. Some of these also bore them- 
selves cells at the bottom ol the water, from which they never 
stir out, but feed upon the mud composing the walls of their 
habitation, in contented captivity ; others, on the contrary, 
range about, go from the bottom to the surface, swim between 
two” waters, quit that element entirely to feed upon plants 
by the river side, and then return to their favourite element, 
for safety and protection. 
The peculiar signs whereby to know that these reptiles will 
change into Hies in a short time, consists in a protuberance 
of the wings on the back. About that time, the smooth and 
depressed form of the upper part of the body is changed 
into a more swollen and rounder shape : so that the wings 
are, in some degree, visible through the external sheath that 
covers them. As they are not natives ol England, he who 
would see them in their greatest abundance, must walk, 
about sun-set, along the banks of the Rhine, or the Seine, 
near Paris; where, for about three days, in the midst of the 
summer, he will be astonished at theirnumbers and assiduity. 
The thickest descent of the Hakes of snow in winter seems 
not to equal their number; the whole air seems alive with 
the new-born nice, and the earth itself is all over covered 
with their remains. The a u re lias, or reptile insects, that 
are as yet beneath the surface ol the water, wait only for 
the approach of evening to begin their transformation. The 
most industrious shake off their old garments about eight 
o’clock ; and those who are the most tardy, are transformed 
before nine. 
We have already seen that the operation of change in other 
insects is laborious and painful ; but with these nothing seems 
shorter, or performed with greater ease. The amelias are 
scarce lifted above the surface of the water, than their old 
sheathing skin bursts; and through the cavity which is thus 
formed, a fly issues, whose wings, at the same instant are 
unfolded, and at the same time lift it into the air. 
Millions and millions of amelias rise in this manner to the 
surface ; and at once become Hies, and (ill every quarter with 
their flutlerings. But all these sports are shortly to have an 
end ; for as the little strangers live but an hour or two, the 
whole swarm soon falls to the ground, and covers the earth, 
like a deep snow, for several hundred yards, on every sid c 
of the river. Their numbers are then incredible, and every 
object they touch becomes fatal to them ; for they instantly 
die, if they even hit against each other. 
At this time the males and females are very differently em- 
ployed. The males, quite inactive, and apparently without 
desires, seem only born to die : no way like the males o 
