They spring all at once from the surface of the water as by magic, hundreds and thousands, yes, millions of them. They fill the air, they cover everything.
The great naturalist Swammerdam, who was the first to make a thorough study of the May flies, thus tells us how they appeared in France one year:—
"I then saw a sight beyond all expectation. The ephemeræ filled the air like the snowflakes in a dense snowstorm.
"The steps were covered to a depth of two, three, or even four inches. A tract of water five or six feet across was completely hidden, and as the floating insects slowly drifted away, others took their places. Several times I was obliged to retreat to the top of the stairs from the annoyance caused by the ephemeræ, which dashed in my face, and got into my eyes, mouth, and nose."
These swarms of May flies appear only from three to five days at a time.
Wherever there are streams there are May flies, and the canals of Holland make good breeding places for them; no wonder, then, the Dutch, who you know live in Holland, have a saying, "As thick as May flies."
Although so many of the May flies perish at once, multitudes of them drop their eggs into the water to renew the race of May flies.
Is it not wonderful that after so long a period of creeping about in the mud as larvæ, these graceful and beautiful little creatures have but a few hours in which to dance joyously about in the upper air on wings of gossamer? Some, indeed, live less than an hour, and some, that come out in the evening, finish their dance of life and perish before sunrise, without ever having seen the beautiful daylight.