The SEE MST ORY 
pended. The fame thing has been obferved 
in thofe Worms that produce Gnats. If at any 
time the air thould happen to efcape from be- 
tween the hairs forming this bubble, the infect 
has the power of immediately replacing it, by 
a new fupply from its pulmonary tubes; and 
fometimes even large quantities of air are feen 
to arife in bubbles from the tail of this Worm, 
6, to the furface of the water, and mix with 
the incumbent atmofphere. This is owing to 
the water’s being fo much heavier than air; it 
being natural for things, though heavy in 
themfelves, to afcend, in order to make way 
for thofe that are more fo. 
This extraordinary operation may be eafily 
feen at any time, by putting the Worm into a 
glafs full of water, and it affords a very enter- 
taining fpectacle ; for the air-bubble, enclofed 
in the tail, looks like a little tranfparent filver 
bladder. I have four fpecies of this Worm, 
and of the Fly that is produced from it, all 
differing in fize and colour; but without any 
other confiderable diftinction. 
As all I have.as yet faid concerning this 
Worm, which produces the Afilus-fly, can 
give but an imperfect idea of it, I thall exhibit 
it alfo as it appears through the microfcope ; 
and, at the fame time, defcribe its external and 
internal parts. Thus the reader will be enabled 
clearly to comprehend the defign and ufe of 
thofe little parts, which are fituated near the 
tail and the mouth; as alfo, after what manner 
its lungs receive the air, which is both admitted 
and difcharged by the tail. Finally, I fhall 
make it evident, that thofe are really the in- 
fe&t’s legs which are feen moving near its 
mouth, like the tongues of Serpents. 
or Gerits 
On examining the external figure of this 
Worm with a microfcope, it appears to be a 
little pointed forwards about the head ; and its 
thorax, or that part of it which we may con- 
fider as fuch, is fomewhat broader. The body 
again grows fmaller, and converges at the ab- 
~ domen,; till at laft it ends in a {harp tail, ele- 
gantly furrounded with hairs, in the form of 
the rays of a ftar. 
This Worm, the head and tail included, has 
twelve annular divifions, 1, 2, 3, 4, 5, 6, 7, 
8, 9,10, 15,12. Its fkin refembles the cover- 
ing of thofe animals which Nature has pro- 
vided with a cruftaceous habit, much more 
than it does that of Worms, or of the naked 
Caterpillars. It is moderately hard, and, like 
that rough {kin called chagreen, it is thick fet 
with an infinite number of {mall grains, pretty 
evenly diftributed. Thefe grains lie fo clcfe 
together, that there is not to be found the leaft 
vacant {pace between them; and they are 
{maller in thofe parts, where the rings of the 
abdomen are pointed to each other, than upon 
the middle of the rings. This difpofition ren- 
_ders the {kin more flexible, and confequently 
facilitates the turnings, and other motions, of 
the Worm’s body. ‘The true conftruction of 
thefe grains is feen, on viewing them with the 
greateft magnifier, Fig.1v. and I give a fepa- 
Of. NS) EY Cady's, AB 
rate drawing of them upon a {mall portion of 
the fkin. This figure alfo fhews us how the 
{kin, 2, looks in the interftices of thofe grains: 
Thofe grains are very thick, and convex in the 
middle, 4: near their edges they appear as 
confifting of many rings, c, which join each 
other ; and forth a great many irregular points, 
d, fo as to add great ftrength and firmnefs to 
the grains themfelves. ‘The fubftance of thofe 
grains is avery firm horny bone; and I make 
no doubt. but the {kin of this Worm might be 
made ufe of, in turning, to polifh the harder 
woods, as ebony and box, in the fame manner 
that the fkin called chagreen, juft now taken 
notice of, is fuccefsfully applied to’ the fame 
purpofe. . 
There are alfo nine puncta refpiratoria, 
breathing-holes, or points of refpiration, on 
each fide of this Worm’s body; but I here re- 
prefent only twelve of them, nine at one fide, 
and three at the other. There are no fuch 
holes vifible on the outfide of the tail, Pig. 111. 
@; nor in the third ring, counting from the 
head: for the tail has, at its extremity, open- 
ings for the admiffion and expulfion of air, as 
already taken notice; and in the third ting the 
breathing-holes only appear under the fkin, 
and are very {mall, as it is hereabouts the em-= 
bryo wings of the future Fly lie concealed. It 
is very remarkable, that this Worm fhould have 
but one ring without thofe breathing-holes ; 
whereas Caterpillars always have two without 
them. The reafon of this difference feems to 
be, that moft Caterpillars change to Flies with 
two pairs of wings; whereas the Worm, un-= 
der our confideration, changes to a Fly that 
has but a fingle pair. 
Above thefe pulmonary openings, there be- 
fides appear a great many black f{pots; but 
they are much {maller than thofe formed by the 
breathing-holes. Thefe leffer {pots feem in- 
tended merely for ornament. They fhed a 
fkin, fo that they are ftill feen in the infect, 
when arrived at the Nymph-ftate. 
The {kin has only three colours: it is 
adorned with oblong black furrows, {pots of a 
little lighter colour, and orbicular rings; from 
the middle of which there generally {prings a 
hair. In the figure before us, only the hairs 
that grow on the infect’s fides are reprefented, 
Tab. XXXIX. Fig. 111. 64; for to exhibit 
them all, would require too large a drawing. 
Befides the hairs already mentioned, there are 
here and there fome other larger hairs, ¢c. 
All the variety of colours perceivable in this 
infect, proceeds from this; that the colour of 
the grains is fomewhat deeper or paler in fome 
places than in others; for there is no material 
difference between them, in point of fize. 
According, therefore, as the number of grains 
is greater or lefs, or the colour of them is 
darker or lighter, the furrows and rings are of 
a deeper or paler colour. 
The head of this Worm, d, is, as it were, 
divided into three parts, and covered with 4 
fkin, the grains on which are hardly dif- 
cernible. ‘The eyes, ee, lie forwards near the 
fnout, 
