The HL2S T/OLR Y we-LNS Eve TS. 
ferves for its conveniency, and by its powers 
enables the Worm to reft or hold itfelf faf- 
pended on the furface of the water. Hence it 
is, that the tail is entirely deftroyed and thrown 
off when the Worm cafts its skin and is changed 
into a Nymph. 
As to the other part of the belly or tail, 
whofe extremity is likewife thaggy, with briftly 
hairs, I exhibit about it fome {mall lumps / of 
an earthy matter, which fall into the water and 
there melt away by degrees. Thefe are the 
excrements voided from the inteftines. We 
may likewife obferve here the intéftines them- 
felves, which contain thefe fceces, and are feen 
through the tranfparent belly, fituated between 
the pulmonary tubes & 4, and at length termi- 
nating in this other extremity of the belly 
which is the real tail. It is very fingular, that 
in this Worm, not only the motion of the in- 
teftines, but alfo the propulfion of the excre- 
ments in them z may be feen through the inte- 
guments of the body. This motion of the 
inteftines, the never-enough celebrated Dr. 
Hook firft difcovered, I obferve likewife that 
thefe pellucid inteftines appear fometimes white, 
fometimes black, and are fometimes divided 
into little knots. This variety arifes from the 
contents and excrements being more or lef 
changed in them. Laftly, I likewife thew fmall 
hairs in the eight rings of the abdomen, three 
in fome, and in others four, and alfo the 
{quamous or fcaly windings and conftruCtions 
thereof, 
When this Worm is arrived at its full 
growth, and its limbs having attained their 
due perfection, are {wollen or filled with blood 
and humours, it throws or cafts off its old 
skin, and expofes to open view all its hitherto 
hidden limbs and parts; this is when it is 
changed into a Nymph, which is delineated in 
its natural fize or bignefs in Tab. XXXI. fig. 
vi. and in fig. vii. as it appears magnified with 
a microfcope. In the latter defign, the head, 
breaft and belly may be more diftin@ly feen 
than in the Worm; nay, and the eyes alfo, 
and the horns, the trunk, the legs and the 
wings. All thefe parts are however fluid like 
water, and muft in due time evaporate this 
moifture in the water, to fuch a degree as to 
acquire due firmne(s. 
Left the delineation of thefe parts fhould be 
_ obfcured by annexing letters to them, I thall 
fhew them all in a lefs finithed figure, which 
I have added for that purpofe. Before I begin, 
it muft be particularly obferved, that the head, 
which before in the Worm hung downwards 
towards the bottom of the water, is always 
raifed upwards in the Nymph, and is likewife, 
by means of two tubes, fufpended on the fur- 
face of the water, in the fame manner as the 
tail of the Worm was before. Hence, as the 
Worm then drew the air through the tail, be- 
ing changed into a Nymph, it now breathes the 
air with its head through the tubes juft now 
mentioned. Hence it is alfo obferved, that the 
tail which in the Worm was protended up~ 
133 
wards, lies in the Nymph funk under the wa- 
ter; and this is indeed a remarkable change in 
the infect with refpe& to its manner of living. — 
One might take thefe tubes in the head for 
the horns which the Worm had before, and 
which are now, after cafting the skin, dilated 
and adapted to another ufe; but thofe horns 
were fituated nearer to the foremoft parts of the 
head. The tail is likewife upon the change of 
its skin confiderably altered; it has acquired 
in this ftate a beautiful feather, to ferve asa 
rudder, by the help of which this N ymph 
moves freely from place to place, and {wims in 
a quite another mafmner than it ufed to do when 
it was in the ftate of a Woritn. Dr. Hooke 
has alfo obferved this change of the Nymph, 
in refpect to the.manner of its moving and 
fwimiming, as appears from his Micrography; 
In many infects, nay, particularly in thefe which 
belong to the fecond mode of the third oder, 
it is obferved that when they ate changed into 
the Chryfalis they have a motion in their tail, 
though all the reft of their body become 
wholly immoveable, as is alfo the cafe in this 
Nymph. We have fully treated of this in the 
beginning of this chapter. 
On one fide of the head in this defign is feen 
an eye, Tab, XXXI. fig. vit. a, covered a 
little on the upper part with a membrane, 
which invefts the probofcis or trunk, and this 
eye, is now divided into hexagonal and globular 
divifions. Above this appears to be fituated one 
of the antennz 4, divided into feveral black knots 
which are fo many joints. The trunk ¢ which 
is the Gnat’s fting, and which partly covers the 
eye, is placed withits fharp point between the legs 
and wings. The legs dddd are ina wonderful 
manner twifted and bent, but efpecially in the 
hinder part; and they are hidden between the 
wings, and appear plainly through the tran{pa+ 
rent fubftance of the latter. This I here exhibit 
delineated, that both the wing of this fide may 
be feen, and alfo the membrane that invefts 
it ee, and which is placed above the legs. The 
body is divided into eight rings, on which fome 
of the hairs, that have changed their outer co- 
vering f/f, are obferved to reft. Through the 
middle of the whole length of the body appears 
a beautiful border or rifing verge z ¢, which I 
could fcarce difcover in the Worm of the Gnat, 
nor have I afterwards found it confiderable in 
the perfect Gnat itfelf. The tail, which hangs 
down, has, as I obferved, a Moving jointed fin A, 
by thehelp of which the Nymph removes from 
place to place. In the upper parts of the head are 
feen the tubulated horns 77 before defcribed, by 
means of which the creature, while in this ftate, 
hangs and breathes on the furface of the water ; 
but by the help of this conftruétion the Nymph 
is now better prepared to be changed into a 
Gnat after cafting its fkin. This infeét, while in 
the Nymph ftate, has no certain colour ; for, 
upon its change, it grows white, and afterwards 
becomes fomewhat green, and at laft it ap- 
proaches to black. 
After 
