re always more or less full of
air-bubbles, which, no doubt, assist in buoying up the insect, and
thus save the expenditure of muscular power. I'll catch one of those
dancing males, and press him quickly in the middle. There! crack he
goes! for the little air-bubbles in the stomach have burst by the
pressure of my finger and thumb.

Abundant as are the May-flies at the latter end of May and the
beginning of June in this country, in other countries they are
sometimes more astonishingly numerous. In some parts of Holland,
Switzerland, and France, their great numbers have been compared to
pelting flakes of snow. "The myriads of Ephemerae which filled the
air," says Reaumur, "over the current of the river and over the bank
on which I stood, are neither to be expressed nor conceived. When the
snow falls, with the largest flakes and with the least interval
between them, the air is not so full of them as that which surrounded
the Ephemerae." The occurrence of such prodigious numbers is, I
believe, unknown in the British isles. In the perfect or _imago_ state
the May-fly lives but a short time. The word _ephemera_ means "living
only for a day;" and though individuals may live longer, yet the term
is fairly correct as expressing their short existence. The May-flies
(_Ephemerae_) have all three long fine hairs at the end of the tail;
some members of the same family, but belonging to a different genus,
have only two hair-like appendages. For instance, the fly known to
fishermen as the "March-brown" belongs to the same family as the
May-fly; it is smaller than it, and has only two hairs at the end of
the tail; but with this exception, the natural March-brown and the
May-fly are wonderfully alike; yet it is most curious to notice what a
wonderful difference there is in the larvae of these two insects.
Significant facts, no doubt, lie at the bottom of such differences in
the case of insects so evidently allied, but these I will not speak
of. Here are the two forms of larvae, the one being the larva of the
common May-fly (_Ephemera_), the other that of the March-brown
(_Baetis_).

[Illustration: LARVA OF BAETIS, WITH BREATHING PADDLES, MAGNIFIED.]

[Illustration: LARVA OF EPHEMERA, OR MAY-FLY, MAGNIFIED TWO DIAMETERS.]

Come, we have lunched, and rested, and watched the May-flies; let us
try to catch a few more trout. It is very strange why sometimes the
fish will not rise, though the weather is propitious and the water in
first-