104 
them, for thofe which begin to live and flutter 
towards the noon of the firft day, are dead be- 
fore night, and the fame happens the fecond 
and third days ; which being expired, no more 
of them are to be feen till the returning year 
again renews this three days wonderful fight. 
At this time the female of the Ephemerus, 
fig. viir. after having thrown off her coat 
or flough, iffues from the water and difcharges 
into it both her ovaries, Tab. XV. fig. 111. 
But this is not done till fhe has for fome time 
fluttered upon the furface of the water ina 
very curious and furprifing manner, beating it 
with her wings all the time. 
It is at this time the female like a fith dif 
charges her eggs, which the male, Tab. XIII. 
fig. xv. who firft quits the water, and afterwards 
divefts himfelf on the land of a very thin 
skin, fig. x11r, and x1y. invigorates by eject- 
ing on them his melt or feminal milky fub- 
ftance. 
I fhall in the fucceeding pages defcribe in a 
full and accurate manner how this act of ge- 
neration is performed, how thefe infects rife 
from the water, and how they free themfelves 
both in the water and on the land of their old 
skins. 
The firft time I obferved this furprifing in- 
fect, was in the year 1661, on a branch of 
the Rhine running by Culenburg. But Clutius 
who has likewife written of thofe infects, fays 
they are to be found at Aarnhem, Zutphen, 
on the canal called Vaart near Utrecht, at Rot- 
terdam, and in many other places. Dottor de 
Mey, a moft reverend and learned divine, has 
likewife given us an exprefs treatife on this fub- 
ject, as appears by the appendix to Goedaert’s 
hiftorical obfervations. Nor has the obfervation 
of thefe infects been confined to our times, 
fome of the greateft naturalifts of antiquity have 
t 
©) deh AR, 
The BOOK of NATURE; or, 
made mention of them, as appears by Pliny, 
Ariftotle, Allian, and others who have written 
on thefe fubjects. We find this little creature 
defcribed in their works by the name of the 
Hemerobion, Ephemerus, and Diaria, as ap- 
pears by many paffages in their works, as like- 
wife by Augerius Clutius’s work, publifhed in 
the year 1634, of which I juft now made 
mention. 
The eggs of the female Ephemerus dropt into 
the water, and there impregnated by an effu- 
fion of the male’s fperm, in the manner we 
have defcribed, gradually fink to the bottom. 
But this is effected in fuch a manner, that the 
eges are {cattered over the muddy bottoms of 
rivers by the motion of the waters. The figure 
of the eggs themfelves does not a little contri- 
bute thereto, as they are of a plain convex 
fhape, Tab. XV. fig. 1. and are thereby the 
apter to difperfe in their defcent. This appears 
by placing a few of them on the point of a 
knife, and then letting them fall gently into 
water, for they immediately feparate of them- 
felves in a very curious manner. 
It is hard to fay, and God only, who gives 
thefe infects life and motion, knows how long 
their eggs lie at the bottom of the waters where 
they are depofited, and how long it is before 
the contained infects break through the {kin 
that furrounds them, and perform as it may 
be called their firft moulting. It is not im- 
probable that thefe things might be experimen- 
tally afcertained by dredging for them at diffe- 
rent feafons, or keeping their eggs in a. vefiel 
full of water with a fufficient quantity of mud 
at the bottom. For the prefent we muft be 
fatisfied to obferve that the eggs of the Ephe- 
merus produce, after an unknown time, a little 
Worm with fix legs. This is the creature fifher- 
men call the bank-bait. 
Il. 
The egg of the Ephemerus produces a little Worm with fix legs, called the bank- 
bait by fifbermen. 
N fearching the bottoms of waters fre- 
quented by the Ephemerus, fome time 
after it has laid its eggs, we find a multitude of 
little Worms with fix legs, which differ in no- 
thing but fize from thofe that are more grown. 
But this is not to be found till a long time after 
the parent infects have made their appearance, 
for the growth of this little infect is fo flow, 
that in the beginning of June in the year fol- 
lowing, about which time the bait turns to an 
Ephemerus, they are fcarce three quarters of a 
Dutch inch long, Tab. XIII. fig. 1. which 
is but about the third part of the length of the 
full grown Worms, fig. 111. that have com- 
plete wings, and are juft upon the point of 
making ufe of them. 
Befides two kinds of Worms remarkably 
differing in bignefs, a third is obferved to be 
produced at the fame time from the mud, 
fig. 11. which is bigger than the leffer kind 
by almoft two thirds, and. isa third part lefs 
than the largeft kind. Nor is this difference 
between thefe Worms in refpect to their various 
age, all we obferve, for thofe of the fame age 
differ greatly both in length and thicknefs. 
When the largeft kind of thefe Worms is about 
three thumbs breadth long, in the beginning of 
June, when they are about to begin to fly; the 
middle kind is not completely two long; and 
the fmalleft is fcarce a thumb’s breadth in 
length. 
There is another remarkable difference be- 
tween thefe Worms of the Ephemerus, which 
is, that the fmalleft kind, fig. 1. not only is 
without wings, or thofe prominences which 
cover the wings, but it does not even rhe Da 
ea 
