THE EPHEMERA. 



781 



striking facts command our attention during 

 the short interval of its fly state ; into which 

 it crowds the most various transactions of its 

 little life. It then may be said to be in a 

 hurry to live, as it has but so small a time to 

 exist. The peculiar sign 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 mere swollen 

 and rounder shape; o that the wings are in 

 some degree visible through the external 

 sheath that covers them. As they are not 

 natives of England, he who would s^e 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 summer, lie will be 

 astonished at their numbers and assiduity. 

 The thickest descent of the flakes of snow in 

 winter seems not to equal their number; the 

 whole air seems alive with the new born race : 

 and the earth itself is all over covered with 

 their remains. The aurelias, or reptile in- 

 sects, that are as yet beneath the surface of 

 the water, wait only for the approach of 

 evening to begin their transformation. The 

 most industrious shake off their old gar- 

 ments 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 aure- 

 lias are scarcely 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 aurelias 

 rise in this manner to the surface: and at 

 once become flies, and till every quarter with 

 their flutterings. But all these sports are 

 shortly to have an end ; for as the little stran- 

 gers 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 side of the river. Their 

 numbers are then incredible, and every ob- 

 ject they touch becomes fatal to them ; for 



I they instantly die, if they hit even against 

 each other. 



At this time the males and females are 

 very differently employed. The males, quite 

 inactive, and apparently without desires,seetn 

 only born to die: no way like the males of 

 other insects; they neither follow the oppo- 

 site sex, nor bear any enmity to each other: 

 after fluttering for an hour or two, they drop 

 upon land, without seeming to receive wings 

 for scarce any other purpose but to satisfy 

 an idle curiosity. It is otherwise with the 

 females ; they are scarce risen from the sur- 

 face of the water, and have dried their wings, 

 but they hasten to drop their eggs back again. 

 If they happen also to flutter upon land, they 

 deposite their burden in the place where 

 they drop. But then it may be demanded, 

 where, and in what manner, are these eggs 

 fecundated, as no copulation whatever ap- 

 pears between the sexes, in their transitory 

 visits in air? Swammerdam is of opinion, 

 that they are impregnated in the manner of 

 fish-spawn, by the male, after being ejected 

 by the female; but, beside that, this doctrine 

 is exploded even from the history of fishes, it 

 is certain that the males have not time for 

 this operation, as the eggs drop to the bottom 

 the instant they arc laid on the water. Reau- 

 mur is of opinion that they copulate; but 

 that the act bears a proportion in shortness 

 to the small duration of their lives; and, con- 

 sequently, must be so soon performed, as to 

 be scarcely visible. This, however, is at 

 best forcing a theory; and it is probable, that 

 as there are many insects known to breed 

 without any impregnation from the male, as 

 we have already seen in muscles and oysters, 

 and shall hereafter see in the gnat, and a 

 species of the beetle, so the ephemera may 

 be of this number. Be this as it may, the fe- 

 males are in such haste to deposite their eggs, 

 that multitudes of them fall to the ground; 

 but the greatest part are laid in the water. 

 As they Butter upon the surface, two clusters 

 are seen issuing from the extremity of their 

 body, each containing about three hundred 

 and fifty eggs, which make seven hundred in 

 all. Thus, of all insects, this appears to be 

 the most prolific ; and it would seem that 

 there was a necessity for such a supply, as in 

 its reptile state it is the favourite food of 

 5Q* 



