42 
3?LI?rT'8 KATUEAL HISTOEY. 
j 
[Book XI. 
medicine,^^ while the rest of the body is deadly. Again, 
liquids turned sour will produce other kinds of gnats, and 
white grubs are to be found in snow that has lain long on the 
ground, while those that lie above are of a reddish^^ colour — 
indeed, the snow itself becomes red after it has lain some 
time on the ground. These grubs are covered with a sort of 
hair, are of a rather large size, and in a state of torpor. 
CHAP. 42. (36.) AN ANIMAL FOUND IN FIEE — THE PYEALLIS 
OE PYBAUSTA. 
That element, also, which is so destructive to matter, pro- 
duces certain animals ; for in the copper- smelting furnaces of 
C^^prus, in the very midst of the fire, there is to be seen fiying 
about a four-footed animal with wings, the size of a large fly : 
this creature is called the pyrallis,'' and by some the py- 
rausta." So long as it remains in the fire it will live, but if it 
comes out and flies a little distance from it, it will instantly 
die. 
CHAP. 43. THE ANIMAL CALLED HEMEEOBION. 
The Hj'panis, a river of Pontus, brings down in its waters, 
about the time of the summer solstice, small membranous par- 
ticles, like a grape- stone in appearance ; from which there issues 
an animaP^ with four legs and with wings, similar to the one 
just mentioned. It does not, however, live more than a single 
day, from which circumstance it has obtained the name of 
hemerobion."^ The life of other insects of a similar nature 
is regulated from its beginning to its end by multiples of 
seven. Thrice seven days is the duration of the life of the 
gnat and of the maggot, while those that are viviparous live 
four times seven days, and their various changes and transforma- 
tions take place in periods of three or four days. The other 
insects of this kind that are winged, generally die in the 
63 See B. xxix. c. 30. 
5* The redness sometimes observed on the snow of the Alps and the. 
Pyrenees, is supposed by De Lamarck to be produced by animalculae : 
other naturalists, however, suppose it to arise from vegetable or mineral 
causes. 
55 Cuvier thinks that he alludes to a variety of the ephemera or the phry- 
ganea of Linnaeus, the case-wing flies, many of which are particularly 
short-lived. These are by no means peculiar to the river Eog or Hypanis. 
"Living for a day/** 
