BUT 
pofed, except the fecond, the third, and the laft. 
Thefe oval openings may be confidered as fo nnany 
mouths, through which the infeft performs the of- 
fice of rcfpiration: and, indeed, it requires no great 
fnare of anatomical dexterity to difcover eighteen 
pair of lungs in the larger kinds of caterpillafs, 
which appear, at firft view, to be hollow, carti- 
laginous tubes, and of the colour of mother-of- 
pearl. Thefe tubes are often feen to unite with 
each other; fome are perceived to open into the 
intefbines; while others lead to different parts of 
the furface of the body. That thefe veffels ferve 
to convey the air, appears evident from the famous 
experiment of Malpighi ; who, having flopped up 
the mouths of the ftigmata with oil, quickly fuffo- 
cated the aniinal. In order to afcertain his theory, 
he rubbed oil on other parts of the body of the 
infcft, leaving the ftigmata free; but this opera- 
tion feemedtohave naeffecfl on the animal's health, 
as it continued to move and eat as ufual: he then 
rubbed oil on the ftigmata of one fide only; 
when the animal underwent a partial Gonvulfion, 
but recovered foon after. However, it ftiould be 
remarked, that the air is not fo neceffary to thefe 
as to the nobler ranks of animals, fince caterpillars 
will exift in an exhaufted receiver for feveral days 
together; and though they may appear to lie 
dead at the bottom, when taken out, they recover, 
and refume their former vivacity. 
If the caterpillar be differed longitudinally 
along the back, it's inteftines will be perceived to 
run in a ftraight line from the mouth to the anus. 
Thefe guts refemble a number of fmall bags open- 
frig into each other, and ftrengthened on both fides 
by a fleftiy cord by which they are united. On 
many occafions the infefts are obferved to caft forth 
the internal coats of their inteftines with their food, 
during the changes they fo frequently experience. 
But rhe inteftines occupy but a fmall part of the 
aniiTial'sbody, if compared with the fat or unftuous 
fubftance in which they are involved. This fubftance 
changes it's colour when the infed's metamorplio- 
lis begins to approach ; and, from white, it is ufu- 
ally feen to turn yellow. If to thefe parts we add 
the inlecft's implements for fpinning, we fliall have 
a rude Iketch of this animal's canformation ; but 
the life of a caterpillar feems only one continued 
I'cene of ilicceftive changes ; and it appears to throw 
oft^ one fkin merely to afllime another, which alfo 
is divefted in it's turn; and fo on for eight or ten 
times fuccefnvely. 
We muft not, however, confound this changing 
of the fkin with the great metamorphofis which the 
infe6l is afterwards doomed to undergo. The 
throwingoff one lkin,and afluming another, feems, 
comparatively fpeaking, but a flight alteration, 
being only the work of a day ; but the other is the 
great adventure of it's life. Indeed, this faculty 
of changing the (km is not peculiar to caterpillars 
only, but is common to all the infe£l tribes; and 
even to fome animals which claim a higher rank 
in the fcale of nature. With refpe6t to caterpil- 
lars, many of them change their flcins five or fix 
times in a fcafon; ajid thefe exuvis fometimes ap- 
pear lb compleat, that many might miflake the 
empty fkin for the real infeft. Among the hairy 
catei-pillars, for example, the caft fkin is covered 
with hairs ; the feet, as well the griftly as membra- 
naceous, remain affixed to it; even thofe parts 
which are only difcoverable by the help of a mi- 
crofcope, are vifible in it; and, in fhort, all the 
parts of the head, the fkull, and the teeth. 
BUT 
In proportion as the time approaches when the 
caterpillar is to diveft itfclf of it's old fkin, it's co- 
lours become more faint; and the fkin, which feems 
to wither, and grow arid in fome meafure, refem- 
bles a leaf deprived of moifture. 
The infeft now begins to feel itfelf under a ne- 
cefTity o-f changing; but this is not effefted without 
vifelent labour, and perhaps pain. A day or two 
before the critical hour approaches, it ceafes to eat, 
lofes it's uiijal aftivity, and feems to grow totally 
torpid. It looks about for Ibme place where it 
may remain in fecurity; and, no longer timorous, 
appears regardlefs of the touch. It is obferved^ 
at intervals, to bend itfelf, and elevate it's back; 
then to ftretch to it's full extent ; fometimes to life 
up it's head, and then to fufter it to drop; fome- 
times to wave from fide to fide, and then to reinain 
in quiet. At length, fome of the rings of it's body, 
particularly the firft and the fecond, are feen to 
fwell confiderably ; the old fkin diftends and bui-fts 
till, by repeated fwellings and contra6i:ions in every 
ring, the animal difengages itfelf, and creeps from 
it's former covering. How laborious foever tliis 
operation may be, it is performed in the fpace of 
a minute ; and the animal, having thrown off it'^s- 
old fkin, feems to enjoy new vigour, as well as ad- 
ditional colour and beauty. Sometimes it afTumes 
a new appearance, and colours very different from 
the old. Thofe infe£ls which are hairy ftiil pre- 
ferve their coverings, though their ancient fkins 
do not appear to have loft a fingle hair ; every one 
of them appearing to have been drawn, like a 
fword from the fcabbard. However, the fa6l Is, 
that a new crop of hair grows between the old 
fkin and the new, and probably helps to throw off" 
the external covering. 
In this manner the caterpillar having continued 
feeding for feveral days, begins at laft to prepare 
for it's change into an aureiia. It is moft proba- 
ble that, from the beginning, all the parts of the 
Butterfly lay hid in this infeft in it's reptile ftatcj 
but that it required time to bring them to per- 
fection, as well as a large quantity of food to en- 
able it to undergo all it's transformations. How- 
ever, when the caterpillar has fed fufHciently, and 
the parts of the Butterfly are formed beneath the 
flcin, it is tlien the feafbn for it to make it's firft 
and principal change into an aureiia, or chryfalis, 
as fome call it ; during which, as has been previ- 
oufly remarked, it feems to remain for feveral days, 
or even months, without either life or motion. 
Preparatory to this important metamorphofis , 
the caterpillar moft ufually quits the plant, or 
tree, on which it is fed; or at leaft attaches it- 
felf to the ftalk or ftem, in preference to the 
leaves. It renounces it's food, and prepares, by 
fafting, to undergo it's transformation. During 
this period, all the food it has fv»'allowed becomes 
entirely digefted; and it often voids even the in- 
ternal membrane which lined it's inteftines. Some 
of the tribe, at this period, entirely change their 
colour; and the vivacity of the tints in all of them 
feems confiderably faded. Thofe which are capa- 
ble of fpinning themfelves webs, let about thefe 
operations : and fuch as have already fpun them, 
await their change in thebeftftate they can. The 
webs, or cones, with which fome of the infedls co- 
ver themfelves, hide the aurelias contained within 
them; but, in others, which are more tranfparent, 
the caterpillar, when it has finifhed it's fpinning, 
ftrikes into the claws of the two feet under the 
tail, and afterwards forces in the tail itfelf, by con- 
trafting 
