43. Chap. 43.-The Animal Called Hemerobion.

CHAP. 43.—THE ANIMAL CALLED HEMEROBION.

The Hypanis, a river of Pontus, brings down in its waters, about the time of the summer solstice, small membranous particles, like a grape-stone in appearance; from which there issues an animal[1] 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."[2] 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 transfornations take place in periods of three or four days. The other insects of this kind that are winged, generally die in the autumn, the gad-fly becoming quite blind[3] even before it dies. Flies which have been drowned in water, if they are covered with ashes,[4] will return to life.

1. Cuvier thinks that he alludes to a variety of the ephemera or the phryganea of Linnæus, the case-wing flies, many of which are particularly short-lived. These are by no means peculiar to the river Bog or Hypanis.

2. "living for a day."

3. They only appear to be so, from the peculiar streaks on the eyes. Linnæus has hence called one variety, the Tabanus cæcutiens.

4. Or with pounded chalk or whitening. Ælian adds, "if they are placed in the sun," which appears necessary for the full success of the experiment. Life appears to be suspended in such cases for a period of surprising length.