252 M U S C A. 
all of one piece, but admit of the contraction and dilata¬ 
tion of that part, according to the circumftances of the 
animal. 
Each of the feet terminates in a fmall bunch of fetes, 
refembling a brush. On the 27th of June, 1816, a paper, 
by fir Everard Home, was read before the Royal -Society, 
giving an account of the meehanifm by means of which 
infedts can walk contrary to gravity, as up perpendicular 
walls, or along the roofs of rooms. In the common bottle- 
fly, every toe is 1'upplied with two fuckers, very fimilar in 
appearance to the pieces of wet leather and firing with 
which boys lift up ltones. Tliefe fuckers, appear to be 
put in adlion by the voluntary inufcles of the infedt. In 
the horle-fiy, each toe is fupplied with three fuckers. 
Thefe fuckers may be feen by means of a lens, when a 
common fly is walking along the infide of a tumbler. 
The author concluded his paper with the defeription of 
certain cufhions upon the feet of fome infedts, to take off 
the elie 61 of a fudden change from a ftate of rapid motion 
to a ftate of reft. 
The interior organization of this genus when examined 
with a proper apparatus, prefents two pulmonary facs of 
a white colour, arranged longitudinally along the body. 
The adtion of the heart may alfo be difeerned, as well as 
the liquor it contains, continually driven along the great 
artery leading to it, and returning by the fame courfe. 
During their larva ftate, flies go through a greater variety 
of metamorphofesTthan eyen the filk or butterfly worms : 
in their progrefs from the vermicular to the chrylalis 
ftate, they pafs through a change unexperienced by other 
infedts. From the fhortnefs of their lives, all thefe vicif- 
fitudes muft rapidly fucceed each other: this circum- 
ftance does not prevent many fpecies from conftrudting a 
cocoon for their lalt metamorphofis, of a curious fabric. 
The greater part of thefe cocoons are of filk, with a mix¬ 
ture of other materials ; thofe molt common with us fatisfy 
themfelves with their own fkin, which becomes an in- 
cruftated covering to protedl them during their dormant 
ftate. When the different members have acquired fiif- 
ficient firmnefs, the fly is ready to burft from its fliell in 
its winged form. The covering of the chryfalis, efpecially 
of thofe that are metamorphoied in their own fkin, would 
feem by its hardnefs an eftedtual bar to that event. About 
the time, however, of its change, the head of the fly is 
capable of being fwollen and dilated in an unufual man¬ 
ner ; and it is by means of this dilatation that the fly 
burfts its covering, and opens a paffage for its elcape. 
The food of flies is as various as their different kinds ; 
fome being fupported wholly by vegetable l’ubftances, 
while others are carnivorous ; and among the latter there 
are fome that only devour flelh in a ftate of putrefadtion. 
The want of accurate inveftigation, fince the fubjedt of 
entomology has been well underftood, leaves us in a ftate 
of uncertainty as to the number of infedts which are nur¬ 
tured within the human body. It feems probable, how¬ 
ever, that the moil frequent inftances which occur, are 
thofe of our mod common domeftic infedt, the varieties of 
the fly. The larvae of feveral fpecies are aquatic, or at 
leaft inhabit moift and wet places, and therefore feem" to 
be adapted to exift in the fluids of the human ftomaoh: 
and the author of the article Insect in Dr. Rees’s Cyclo¬ 
paedia ftates, thar he is in poffeffion of fome larvae of the 
common houfe-fly, which were rejedted alive from the 
ftomach of a man by vomiting; (fee Edin. Med. and Surg. 
Journal, for Jan. 1S11, p. 41.) and of others of the fame 
fly, which were palled by ltool by another perfon. The 
larva of another fpecies of fly is alfo figured, in the Jour¬ 
nal juft referred to, by Dr. Cheyije, now' of Dublin: and 
feveral examples of the larvae of flies, dilcharged from the 
human inteftines, are on record. Dr. Wahlhom, ofUpfal, 
has related the cafe of a girl, who, after fuffering confider¬ 
able pain in the ftomach and left fide, dilcharged by ftool 
a number of larvae on feveral fuccelfive days, after which 
ihe was relieved from the complaint. One of thefe larva, 
phile it was kept in a phial, was converted into a fly, 
3 
which proved to be the Mnfca nigra of Linnaeus. Dr. 
Wahlhom alfo ftates, that a few years ago there was a girl 
in Upfal, from whom a large quantity of worms were 
brought away, and thefe w r ere fli/-ivorms; for an account 
of which he refers to Dr. Dubois’s Treatife de Taenia. 
(See Med. Chirurg. and Anatom. Cafes and Experiments, 
communicated to the Royal Academy of Sciences at 
Stockholm, 1757, cafe 24.) Ruyich has deferibed and 
delineated both the larvae and the flies which originated 
from them, after they were difeharged (it is affirmed) by 
urine, by a nobleman, in confiderable quantities; and 
Tuipius has mentioned a fimilar cafe, and has alio figured 
the larvae, which clofely refemble thofe of the fly. 
As the fpecies are fo extremely numerous, at the fame 
time that of fo many of them very little is known, we 
fhall refrain from exhibiting a dry catalogue of 511 in¬ 
fedts; but lhall leledt for delcription and figures fome of 
the moll remarkable. And, this being the cafe, we lhall 
premife a few more general remarks, being the fubftance 
of a ledture or diflertation by the late ingenious Mr. Curtis, 
author of the Flora Londinenlis, &c. and communicated 
by Mr. Bracy Clark to the editor of the Monthly Maga¬ 
zine. 
Mr. Curtis denies palpi, or feelers, to this tribe; and he 
adds to that part of the generic character which relates to 
the exjerted flelhy probolcis, “ capable of being drawn in 
clofe to the head which he thus explains : “ If w'e atten- 
tentively obferve the common houfe-fly, when it vifits the 
tea-table in fearch of food, we may very dillindtly fee it 
put forth its probofeis to luck up any fweet liquid, and it 
then appears of a confiderable length ; but, if we catch the 
lame fly, we find its probofeis drawn in clofe to its head.” 
On examining the extremity of it with a magnifying glafs, 
we find it furniffied with two mufcular lips. Befides this 
peculiar ftrudture of the trunk, which furnilhes the moll 
effential character, the antennas are deferving of fome at¬ 
tention. They are compofed of feveral fmall and Ihort 
pieces or joints, the terminal one of which is generally 
iargeft, and frequently flattened; from the middle or 
bottom of this terminal joint generally proceeds a lateral 
hair, which is lometimes Ample, fometimes feathery; 
hence the Mufcas are divided into fuch as have antennas 
nudesJ'etariee and plumojce. 
The body of the larvae is compofed of twelve joints, 
which run tapering towards the head. The head itfelf is 
final!; the mouth is armed with a hard and pointed kind 
of dart, contained within a cafe notched on the fore part, 
which ferves it inftead of jaws. Thefe larvae have four 
breathing-holes, two of which are placed anteriorly, one 
on each fide ; the two others at tlie extremity of the body; 
they have no vifible eyes. 
Authors have remarked, particularly Mr. Keller, painter 
of Nuremberg, who has written the hiftory of the com¬ 
mon houfe-fly, and illuftrated it with moll elegant plates, 
in which the leveral parts of the infect are highly mag¬ 
nified, that they are uncommonly tenacious of life; he 
applied oil to leveral of them, which, though it proved 
inltantly fatal to fome caterpillars of moths, produced no 
eifedt on them ; they even furvived feveral hours’ immer- 
fion in oil. Oil of turpentine however killed them in half 
an hour. See alfo the article Entomology, vol. vi. p. 843. 
According to Mr. Keller, the eggs of the common 
houfe-fiy were hatched in twenty-four hours after being 
depofited: in fifteen or lixteen days they changed to 
chryfalis, in which ftate they remained about the fame 
time before the perfect infedt was produced. The ha¬ 
bitation of thefe larvse varies according to the different 
fpecies of flies to which they belong. Many of them, 
have alfo fome peculiarities which deferve notice. There 
are lome which are found on trees and plants, feed¬ 
ing on and making great havock among the Aphides, 
or plant-lice, the molt deftruftive infect which can infell 
any tree or plant, and the moll common caufe of what 
are called blights. Thefe have a long body, capable of 
ftill greater extenfion; they ltretch out their heads; and. 
