ON THE 
TRANSFORMATIONS 
OF THE 
COMMON HOUSE FLY, 
WITH NOTES ON ALLIED FORMS. 
I3Y 
A. S. PACKARD, Jr., M.D. 
From Proceedings of the Boston Society of Natural History. 
Vol. xvi, February, 1874. ON TIIF. 
TRANSFORMATIONS 
OF THE 
COMMON I-IOXJSE FLY, 
WITH NOTES ON ALLIED FORMS. 
BT 
A. S. PACKARD, Jr.,' M.D. 
From Proceedings of the Boston Society of Natural History. 
Yol. xvi, February, 1874. Ox the Transformations of tiie Common House Fly, with 
Notes on allied Forms. By A. S. Packard, Jr., M.D. 
It is not a little strange that the history and transformations of the 
common House Fly are so little known. There is a vague idea that 
it breeds in the manure of stables, but no one in this country lias in- 
vestigated its habits, and even Dr. Harris, by describing our common 
species under a separate name, seems to. indicate that ours is not the 
common House Fly of Europe. In Europe, even, but little attention 
has been given to its habits. They are mentioned only in three 
works, one of which (by Bouehe) was published during this century, 
with figures so poor and inadequate as to be actually misleading. 
Having been fortunate enough to find the larva; of this species in 
large numbers, and then to induce the adults to lay eggs in great 
abundance at our own pleasure, as it were, we make the attempt to 
clear up the history of the development and transformations of 
Musca domeslica Linn. 
Bibliography. After Linnaeus had described this species as the 
Musca domes!ica, DeGeer 1 was the first to satisfactorily describe its 
transformations. He says that the larva lives in warm and humid 
dung, but does not say how long it lives in the egg, larva, or pupa 
state. lie gives a good description of the larva, stating that its pro- 
thoracic stigma ends in six divisions, and adds, “ Ces larves, que sont 
absoluinent sans pattes, n’ayant pas mcme ccs mamelons charnus 
qu’on observe ii celles de la viande [Musca carnaria] et de quelques 
autres especes, se sont des cocques de leur propre peau, mais qui 
n’ont rien de particulier h otfrir et les moucliesen sortent peu de jours 
apres (p. 78, Tome C, 1776). 
In 1831 Louche 2 described the larva, remarking that it lives in 
1 Carl De Geer. Me1 moires pour servir si l’Histoire des Insectes. Stockholm, 4° 
1752-’78. 
11’. Fr. Bouchg. Naturgeschiclite der Iusekten, etc. Berlin, 1834. 12°. The 
third work we have alluded to is by Keller; Geschichte der gemeiner Stubenfliege, 
1704 and 17%. This last we have not seen. 137 
1873.1 
[Fackard. 
horse’s and fowl’s dung, especially when warm. He does not, how- 
ever, state how long it remains in this state. After a fair description 
of the pupa-case, he says that it remains in this state from eight to 
fourteen days. His figures of the larva and pupa-case are very poor, 
not being recognizable; but this is the only time, so far as we are 
aware, that the insect has been figured in its preparatory stages. 
We have been unable to find any other references, of any import- 
ance from a biological point of view, to this commonest of insects. 
Embryology. During the month of August the House Fly is ex- 
tremely abundant, and as we, and others, have noticed, especially so 
in the neighborhood of stables. On placing one fly in confinement 
in the shade, enclosed in a glass bottle, she laid some time between 
six p. M., August 12tli, and eight A. M., August 13th, one hundred 
and twenty eggs. They were deposited irregularly in stacks, as it 
were, lying loose in one or two piles at the bottom of the bottle. At 
eight a. m., August 14tli, several were found hatched out and crawl- 
ing about the bottom of the bottle. 
In order, however, to obtain a large number of eggs, we placed a 
mass of freshly dropped horse manure, still warm, at an open window 
in the sun. This attracted large quantities of flies for three or four 
weeks succeeding, which laid eggs during that period. Immediately 
on exposing the manure on the morning of the 12th of August, the 
flies appeared and laid their eggs in masses in the crevices in the 
manure, working their way down mostly out of sight, and depositing 
bunches of eggs in various convenient places. These were found 
hatched out at about the same hour the next day. From several 
such experiments made on different occasions, we may regard the 
embryo as requiring twenty-four hours for perfection. In confine- 
ment it requires from five to ten hours more, and those larvae hatched 
in confinement are smaller than those reared from eggs deposited in 
warm manure. It is evident that heat and moisture are required for 
the normal development of the larva, as usual in all insects. Thus 
the egg state lasts for twenty-four hours, about the time of that of 
Musca vomitoria, according to Weismann,1 who states that it lasts 
from seventeen to twenty-six hours. 
The egg is elongate oval cylindrical, a little smaller, more pointed 
at the anterior end than the posterior. It is .04-.05 inch long, and 
1 Die Entwickelung der Dipteren im Ei, nacli Beobaclitungen an Chironomus, 
Musca yomitoria und Pulex canis. Zeitschrift fiir Wissenschaftliehe Zoologie xin., 
p. 107-204. 1864. 138 
Packard.] 
[Nov. 19, 
about .01 inch in diameter. The chorion is thin and structureless, 
but covered by an outer shell, which renders the egg quite opake, so 
as to prevent one from making out the earlier embryonic changes. 
It is evidently secreted and laid upon the chorion just before the egg 
is laid. Its surface is pitted with elongated hexagonal depressions, 
which cross the egg transversely. Compared with the eggs of Calli- 
phora vomitoria, the Meat Fly, they are rather smaller, those of the 
latter being .0G inch in length, and thicker in proportion, while the 
hexagons are in the Meat Fly larger and longer. The eggs of both 
flies are dull chalky white. 
The micropyle is round, and easily perceived on twisting the egg 
under the compressor. 
The yolk granules are exceedingly fine, as in C. vomitoria, so that 
the yolk is quite dense. 
Owing to the density of the exocliorion, as we may term the outer 
shell, it was impossible to observe the earliest embryonic changes, 
the formation of the blastoderm, and the primitive band. From one 
specimen hardened in alcohol, we succeeded in tearing off’ the exo- 
chorion by aid of the compressor and needles, an operation which we 
could not succeed in doing on recent eggs, as they invariably broke. 
This stage apparently agrees with that of Calliphora vomitoria, fig- 
ured by Weismann on Taf. V., figs. 65, GG. 
A more advanced stage, as seen through the exochorion, is repre- 
sented by Weismann’s figures 71 and 72. 
At a more advanced stage (FI. 3, Fig. 1) the embryo is nearly fully 
formed. The segments and locomotive spines crossing the under 
side of each segment are formed. The head is indicated; the two 
tubercles probably indicating the 1st maxillae. The head is much 
larger compared to the size of the prothorax, than subsequently, and 
the dark Y-shaped twin spots indicate the formation of the oesopha- 
geal frame work. The anal spiracles are formed, but the spiracles are 
still somewhat rudimentary, though the tracheae leading from them 
appear to be fully formed. 
Just before the embryo hatches, the body becomes more transpar- 
ent, and, as seen in Fig. 2, the main tracheae can be traced through 
their whole length, with their lateral and cephalic branches. The 
rows of locomotive spines are very distinct. They can be easily seen 
in the egg in its natural state, but the figure represents the living egg 
with the exocliorion removed, this covering having already split 
along the under side, just as we have seen it in C. vomitoria. 1873.1 
139 
[Packard 
We feel warranted then in stating that the embryological develop- 
ment of Musca domestica is in all its stages almost identical with that 
of Calliphora vomitoria, so elaborately worked out and copiously 
illustrated by Weismann, in his famous work. 
When the embryo is about to slip out of its egg-membranes, includ- 
ing the amnion, which we have observed to be as usual in the in- 
sects, it is quite active in its motions, the body moving to and fro 
within the shell. Undoubtedly this motion, accompanied by a twist- 
ing motion of the body, ruptures the exchorion. 
We did not witness the process of hatching of the House Fly, but 
have no doubt it is like that of the Meat Fly (C. vomitoria). A larva 
of the latter hatched under our eyes. The egg-shell split longitud- 
inally, and in one or two seconds it pushed its way out through the 
anterior end, and in a second or two more extricated itself from the 
shell. The shell scarcely changed its form, and the larva left the 
amnion within. 
The larva. First stage. (PI. 3, Fig. 3, 3b) In order to bring out 
more clearly the characters of this stage, we shall compare it with 
the freshly hatched larva of the Meat Fly (C. vomitoria), which we 
studied at the same time in order to test our work on the House Fly. 
The larva as soon as hatched, on being compared with that of the 
Meat Fly of corresponding age, differs from tlio latter in being slen- 
derer, with the head in front rounder and narrower, while the poste- 
rior end of the body is rounder and narrower. The sutures in M. 
domestica are much less plainly marked, especially the three anterior 
ones. There are but seven rows of locomotive spines, where in C. 
vomitoria there are twelve, one for each segment (Weismann does not 
figure the last and minute row). Moreover, the spinulcs are less 
numerous than in C. vomitoria. These rows of spinulcs appear more 
clearly than in the fully grown larvae in both genera. These differ- 
ences we would regard as good generic characters, and these arc, with 
the other characters given below, the only differential characters by 
which to distinguish the larvae. 
The head is much less free from the succeeding, or prothoracic, 
segment than in C. vomitoria, the suture behind being less distinct. 
The end of the body below the stigmata docs not project so conspic- 
uously as in C. vomitoria. 
There are also good generic characters in the trachea?. In M. do- 
mestica the two main trachea? are more sinuate, and do not taper so 
rapidly anteriorly, while the distance from the posterior commissure Packard.] 
140 
[Nov. 19, 
to the stigma is greater, and the dark terminal portion longer, than 
in C. vomitoria. The secondary branches arc rather shorter than 
in C. vomitoria, and the two inferior medio-posterior tracheal twigs 
(Fig. 3 b) arise behind the posterior commissure. The tracheal twigs 
of the head are distributed much alike in both genera. 
The length of the freshly hatched larva of M. domestica is .07 inch. 
It remains in this stage about twenty-four hours. 
The second stage. (Fig. 4.) This stage is signalized by the addi- 
tion of the prothoracic stigmata. This change must necessarily, 
though we did not perceive it, be accompanied by a moult of the first 
larva skin, as in Calliphora vomitoria, according to Leuckart1 and 
Weismann (/. c.). 
The length of the larva at this stage varies from .15—.17 inchin 
length. It is considerably slenderer than in the first stage. We are 
inclined to think that this stage lasts from about twenty-four to thirty- 
six hours. One of these larvae grew .05 inch in twenty-four hours. 
The third stage. As this last stage does not differ from the preced- 
ing one in any important respects except size, the following descrip- 
tion will apply to both. 
The larva of M. domestica differs from C. vomitoria in being 
proportionally longer and slenderer, more regularly conical, the body 
gradually increasing in width to the end, which is square. The prop- 
leg is small and inconspicuous as compared with that of the other 
genus, and cannot be seen from above when the larva is in motion. 
In Calliphora the body narrows towards the end, the stigmatal hollow 
is very well marked, with eight large subacute conical tubercles on 
the elevated edge of the round area, which in life is stuck outwards 
and upwards, j>resenting a cup-like hollow, at the bottom of which 
the stigmata are situated. They are large and tun-shaped, deep 
testaceous in color, with fine longitudinal whitish stripes ; while in 
Musca domestica they are black, external, being situated in a very 
slight depression, and are very conspicuous. 
The anal spiracles in M. domestica (Fig. 5; 5 a, still more enlarged 
spiracle of a younger larva than 5) are rounded, forming about three- 
fourths of a circle, with the opposing sides square, and a broad dark 
chitinous ridge, which becomes wider and darker with age. The 
openings are two, very unequal, the longer one apparently formed by 
the union of what were probably originally two openings. These 
1 Die Larven Zustiinde dcr Musciden. Arcliiv fur Naturgescliiclitc, 1861, p. CO. 1873.] 
141 
[Fackard. 
openings are very sinuous, the fissure guarded by dense projecting 
cones. This sinuate course of the spiracles is the most prominent 
differential character of the genus Musca. Fig. 6 shows their dispo- 
sition in Calliphora vomitorici, and Fig. 7 their arrangement in Sarco- 
phaga carnaria, being slenderer and situated farther apart in the 
latter genus. 
The spiracle on the prothoracic segment (Fig. 4 c) is divided into 
six lobules, rarely into eight. Fig. 4 d shows the end of one of these 
lobules, with a corrugated rim, and a central slight fissure for the 
admission of air. 
The head (Fig. 4 a) is conical, about half as long as the protho- 
racic segment in the larva of the second stage, but much smaller 
proportionally in the fully grown maggot. The antennas are minute, 
conical, two-jointed, the terminal joint minute, acutely pointed. 
Below are two fleshy tubercles, probably representing the maxillae, 
and a single one, representing possibly the labrum, or upper lip. The 
black hoirny mandibles are of the usual form of the family. 
The body of the maggot is much more transparent than in Calli- 
phora or Sarcophaga. The region next the sutures, between the 
segments, is scarcely thickened, while it is conspicuously so in Calli- 
phora, and the tegument is smooth and shining, while in Calliphora it 
is opake and finely shagreened. 
Length when fully grown, .25-.40 inch (while C. vomitorici meas- 
ures .55-.60 inch). It probably remains in this state about three or 
four days. The entire life of the larva is, then, from five to seven 
days. 
We are inclined to think that the larvae, if hard pressed for food, 
devour each other, as of four larvae put in a bottle, only two were 
found the day after. In the manure they eat up the decaying matter, 
leaving the bits of hay and straw. 
Among the literally thousands of larvae which have passed under 
our eyes, we have not as yet been able to detect an individual in 
which the body had decidedly contracted and changed its form pre 
paratory to the formation of the puparium, and are inclined to 
believe this to be a comparatively sudden act. 
For convenience in comparison, and to make this essay more com- 
plete, we give a brief description of the larva of Sarcophaga carnaria 
the maggot of the common Flesh Fly, which has been known to be 
an inhabitant of this country for about a century, as DeGeer men- 
tions it in 1776, in his “ Memoires,” as having been received from Packard.] 
142 
[Nov. 19, 
Pennsylvania. It is closely similar to Calliphora vomilorin, but a little 
longer. There are eleven divisions or lobules to the prothoracic stig- 
mata, where in Calliphora vomitoria there are nine. The locomotive 
spines are more acutely pointed. The anal spiracles are of the same 
relative size as in Calliphora, but the openings are much longer and 
narrower, and consequently farther apart, and the circular orifice in 
the peritreme is wanting; in both genera the peritreme is round, 
while in Musca it is somewhat hemispherical. The fleshy projections 
around the spiracular depression, and the two fleshy prop-legs are the 
same in the two genera, Sarcophaga and Calliphora, while the head 
and its appendages present no differences. The only character by 
which to distinguish the larva? of the two genera is in the form of 
the stigmata. The mode of life, and of taking food, is identical in 
the two; they differ but slightly in size, and here we have in the 
preparatory state of two allied genera, no specific characters devel- 
oped, the differential ones are generic in their nature. And yet the 
imagines are very different, with a number of specific characters 
separating them. , 
The puparium (Fig. 8, ventral; 8a, dorsal view, enlarged) is reg- 
ularly cylindrical, at the fifth segment from the head beginning to 
taper regularly towards the head, the anterior end being distinctly 
pointed, the rudiments of the head and prothorax being small. Pos- 
teriorly the body is much rounded, full and obtuse, with no spiracular 
depression nor spines surrounding it, but the spiracles are situated 
conspicuously like little buttons on the end. On the dorsal side of 
the body is a single row of coarse granulations along the suture, be- 
coming beneath double, with fine lines crossing and connected with 
the granulations, the distance between the rows widening posteriorly- 
Numerous granulations, rather finer than those anterior, surround the 
rudiments of the prop-legs. A raised sharp prominent lateral ridge 
extends on each side from the mesothoracie segment on to the first 
abdominal. Prothoracic spiracles very minute, with usually six lob- 
ules, and not extending beyond the mouth parts. The prop-legs are 
represented by two oval flattened parallel contiguous tubercles, with 
a rather remote and obscure area on each side. The anal spiracles 
form black, round, flattened, button-like tubercles, the terminal seg- 
ment being smooth and shiny, and regularly convex. 
Length, .20-. 2 7 inch. 
So remarkably similar is the puparium of Musca domestica to that 143 
[Packard. 
1873.] 
of Stomoxys calcitrans1 (Fig. 10, dorsal; and 10 a, ventral view of an 
immature puparium, in which the pupa is very rudimentary, the ab- 
domen being continuous with the thorax) that it is difficult to give 
any characters by which to separate them. The two most impor- 
tant ones are the following; the anal spiracles of Musea domestica 
(Fig. 9) are larger, much closer together, square on the opposing 
faces, and depressed in the middle, while those of Stomoxys calcitrans 
are remote, round, and flat topped. (10 c.) The lower side of the 
end of Stomoxys is darker and much more rugose, owing to trans- 
verse ridges, than in Musca, where it is comparatively smooth. Fig. 
10 6 gives an idea of these ridges and transversely oval enclosures. 
The ridges lying between the spiracles and the region of the prop- 
legs are wanting in Musca domestica. 
In both genera the protlioracic spiracles of the pupa connect with 
similar projecting, slightly twisted, long acute points which are situ- 
ated on each side on the hinder edge of the metatlioracic segment of 
the puparium. These stigmata are not represented in either of the 
drawings of the puparia we here present. The divisions of the pro- 
tlioracic stigmata in the puparium of Stomoxys are five in number. 
The puparia of this species occurred more abundantly with us than 
those of the Domestic Fly, and were at first mistaken for them. The 
puparium of M. domestica may at once be distinguished from Cal- 
lipliora and Sarcopliaga by the obtusely pointed (compared with 
those of C. vomitoria and S. carnaria) end, and the full rounded hind 
end, with the spiracles externally like buttons; also by its smaller 
size, and by the double row of large granulations, while in Callipliora 
and Sarcophaga there are twelve or more. 
In Musca, as well as in Stomoxys, when the pupa is formed, the 
hard frame work of the jaws of the larva rest next to the skin of the 
puparium, and always on the ventral side, and apparently in connec- 
tion with the old larva skin. When the fly pushes its way out of the 
pupa case, the anterior end of the latter splits off' just behind the su- 
ture between the metatlioracic and first abdominal segment. And 
often when the front end of the puparium is forced off, the ventral 
half, with most of the rudiments of the mouth-parts, remains attached 
to the case. 
A parasite found in the puparium of Musca domestica will be de- 
scribed at the end of this essay. 
1 As has been noticed by Bouchg (l. c., p. 50) as regards the larval state. Packard.] 
144 
[Nov. 19, 
The puparium of Calllpliora vomitoria is cylindrical, slender, flask- 
shaped, being thickest on the anterior third of the body, thence grad- 
ually narrowing to the posterior end and suddenly contracting, leav- 
ing a well marked neck, which is much darker colored than the rest 
of the body, which is of the usual dark red color. The spiracles are 
quite prominent, extending as far as the extreme tip of the head; 
they are of much the same form as in the larva, and with from twelve 
to thirteen deeply marked divisions. (In one larva there .are nine 
lobules.) 
Two broad bands and a narrow linear accessory line of minute 
granulations cross each segment, and become curved a little ante- 
riorly along the dorsal line. The constricted end of the case is pro- 
vided with twelve prominent rugose granulated spines, with longitud- 
inal ridges on the neck terminating between the spines; and along 
the ventral side of the neck is a ridge, less sharp and prominent than 
in Sarcophaga, and with larger granulations. The rudiments of the 
prop-legs consist of two lateral conical projections and a median 
furrow. The projections are a little farther apart, and more slender 
fhan in Sarcophaga, but the differences are very slight. The dorsal 
ridge ending between the two uppermost eircum-anal projections is 
obscurely marked, while in Sarcophaga it is distinct and sharp. 
The divisions of the stigmata are very plainly and deeply cut, 
while in Sarcophaga carnaria there are no indications of the incisions, 
the edge being rugose, but not crenulated. 
This is the. most important distinguishing 
mark in the puparia of the two genera. 
Length .30-.35 inch. 
The puparium of Sarcoj>haga carnaria 
(described from specimens received from 
Rev. Mr. S. Lockwood) is twice as bulky 
as that of Calliphora vomitoria. It is cylin- 
drical, not tapering so gradually posteriorly 
as in C. vomitoria, and not contracted at the 
end into so long a neck. The twelve blunt 
spines surrounding the spiracular region are 
much smaller, less conspicuous, and do not 
project, except the two lower ones, beyond 
the end of the puparium. The ridges ending 
between these spines are much higher and 
sharper than in C. vomitoria. The dorsaj 
Puparium of Sarco- 
phaya carnaria. 1873.] 
145 
[Packard. 
ridge on this neck is much sharper and more pronounced’ than in 
C. vomitoria, and the impressed lines on the sides extend forwards 
to the suture between the penultimate and terminal segments of the 
body, the lines curving outwards anteriorly. There is a well-marked 
pointed short ventral ridge behind the rudiments of the ventral prop- 
legs. This ridge is obscurely marked in the puparium of C. vomi- 
toria, except that the prothoracic spiracles are much less prominent, 
not projecting beyond the head, their extremities being just parallel 
with the end of the rudimentary mouth-parts. The edge of the 
spiracle is rugose, but I have been unable to distinguish any signs 
of lobules. The lines of pointed granulations are arranged much as 
in C. vomitoria. Length .50 inch. 
The pupa. (Fig- 11.) The pupa of M. domestica may at once be 
known by its broad spatulate labium or tongue, and the curved, al- 
most elbowed maxillary palpi. The antennae (Fig. 11c?) are dis- 
tinctly three-jointed, with a large, stout bristle. Fig. 11a sliows one 
of the leas with the trochanter lianaina to it; Fia- 11 h the wina, sur- 
rounded by its membrane; and Fig. 11c the optic lobes, and their 
connection with the unorganized cornea and facets of the eyes; the 
outer surface of the eye being covered with fat cells, destined to form 
pigment cells, which finally turn reddish. 
The figures 12, 12 a, 12 6, show the corresponding stage in the 
pupa of Stomoxys calcitrant; here can be seen the generic characters 
which separate this fly from the House Fly, i.e., the elongated beak, 
the smaller, narrower, more pointed head. The mouth-parts with 
the long maxilla! (nix') and mandibles (in), and the straight maxillary 
palpi, are shown in the enlarged view (Fig. 12 c). 
On removing the puparium we were able to obtain a portion of the 
semipupa of Stomoxys (Figs. 13, 13 a) i.e., the thorax, the head adher- 
ing to the pupa-case, and only the basal segment of the abdomen 
being brought to vie\V; enough, however, to show that they were 
nearly of the form of those of the larvaj. This stage compares almost 
exactly with that of Callipliora vomitoria, as figured by Weismann, 
Tab. xii., Figs. 38, 39, 40. This stage is intermediate between 
the larval and pupal, and may be properly termed the semipupa.1 
1 Professor von Siebold, in his “Beitriige zur Parthenogenesis (ler Artliropoden,’’ 
1871, p. 35, calls this stage pseudo-nymph. As this state is necessarily universal in 
all metabolous insects, it seems incorrect to regard it as a false or unusual state, and 
we therefore may be pardoned for retaining the name first proposed by us in 1866. 
(l’roc. Bost. Soc. N. H., x, 279.) 
PROCEEDINGS B. S. N. H. — VOL. XVI. 10 FEBRUARY, 1874. Tackard.] 
146 
[Nov. 19, 
Similar intermediate stages have been shown by us to exist in the 
Hymenoptera, Lepidoptera, and Coleoptera, and in other Diptera. It 
shows that the distinction between the larval and pupal stages are 
as truly artificial as in the ametabolous insects. 
Fig. 13 is a dorsal view of the three thoracic segments, with the 
anterior leg attached, and the wings. The segments are very indis- 
tinctly marked. The prothoraeic stigmata are very near together* 
though so widely separated in the fully formed pupa. Fig. 13 a is a 
ventral view of the same parts, the parts somewhat distorted; it also 
represents the wings, and the two hinder pairs of legs, and 13 b the 
fore leg; the joints of the legs are clearly indicated. 
The next stage in the pupa of Stomoxys was much farther advanced, 
the thorax being formed much as in the mature pupa, as also the ab- 
domen. The body is still much longer than in Fig. 12, the head nar- 
rower and freer from the body, and the vertex more elongated. The 
mouth-parts do not reach much beyond the anterior third of the body, 
while the wings reach only to the middle of the body (the head ex- 
cluded), and the hindermost legs only reach a little beyond the mid- 
dle of the body (the head excluded), and a little way beyond the end 
of the wings. Viewed dorsally, the thorax is much shorter than in the 
stage represented by Fig. 12, and the scutellum is short and 
being still quite rudimentary. The form of the eyes can just be 
distinguished, and the antennae can with difficulty be perceived. 
Fig. 12 represents the succeeding stage of the pupa of Stomoxys, 
which may be said to fairly represent the typical pupa condition of the 
cycloraplious diptera. At this time the body is pure white, the eyes are 
unchanged in color, and under low powers there are no traces of hairs 
to be seen. In this and the following stages the proportion in the 
length of the wings and legs, and mouth-parts, remains nearly the 
same. The wings reach to the middle of the abdomen, while the hind 
legs just pass beyond the tip end of the abdomen. The mouth-parts 
reach to the second abdominal segment. The eyes and antennm are 
clearly indicated (the latter not shown in the drawing). The stages 
beyond differ but slightly, and form exceedingly gradual steps towards 
the imago. They differ chiefly in the degree of maturity of the tegu- 
ment and hairs. In one example, in which the sutures are much 
more distinct than in Fig. 12, the body is slightly dusky, but the eyes 
are beginning to turn rosy around a portion of the edges. The hairs 
are also apparent. In a more advanced stage the eyes are a deep 
scarlet, the hairs are brown, the wings and legs are dusky. 147 
1873.] 
[Packard. 
The prothoracic spiracle, with its black, corneous tip, is much the 
same in all the specimens. 
Having had more alcoholic specimens of the pupa of Stomoxys 
than of Musca, we have not been able to trace these stages in the 
latter genus, but doubt not that similar ones occur in all the Muscidae. 
I'he imago. On leaving its puparium the fly runs around, with its 
wings soft, small and baggy, much as in the pupa. They reach a 
little beyond the middle of the abdomen, and are still pressed to the 
side of the body. It is pale, as in the puparium, and the colors are 
not set. The membranous portion of the front is constantly distend- 
ing as the fly walks rapidly about. When this part is contracted it 
forms a dull livid area, soft and fleshy, free from hairs. This portion 
suddenly distends into a bladder-like expansion, trapezoidal in out- 
line, equal in bulk to the rest of the head, and pushing the antennas 
down beneath out of sight. This thin membrane is evidently dis- 
tended with air, and its connection with the tracheae, and the mech- 
anism of its movements, would form a most interesting subject of 
inquiry. This part has been described by Mr. T. B. Lowne, in his 
work on the “ Anatomy of the Blow Fly,” and he is evidently cor- 
rect in regarding it as an organ for pushing away the end of the 
puparium when the pupa slips out of its case. 
The common House Fly, though so abundant, is difficult to distin- 
guish from the allied species. The generic characters may be found 
in the mouth-parts, already described by authors. In the venation of 
the wing it differs decidedly from Sarcophaga, in the end of the me- 
dian vein being bent nearly at right angles, and in being regularly 
but slightly incurved, while in Sarcophaga, it is bent at a much lower 
angle, being much more oblique. From the genus Lucilia, which it 
much nearer approaches structurally, it differs in this vein being still 
bent at a greater angle, and in having the bent extremity more curved. 
In Stomoxys this vein is but slightly bent, thus widely differing, be- 
sides in its remarkably long horny beak, from Musca, with its short 
fleshy bilobed tongue. 
The body of M. domestica is black; the head has a longitudinal 
reddish oval smooth area on the vertex, with the orbits and adjacent 
region golden (or silvery in some lights); the hairs are black, and 
the antennas and plume are black. The thorax is black, tinged with 
golden gray on the sides, with three dorsal gray longitudinal bands, 
the middle one most distinct, the two lateral ones partially inter- 
rupted in the middle and continued on to the scutelluin; there is a 148 
[Nov. 19, 
Packard.] 
broad lateral golden gray band interrupted by the sutures. The base 
of the first abdominal segment has a yellowish band, interrupted in 
the middle. On the middle of the end of the two succeeding seg- 
ments is a triangular mesial golden spot, with an oblique irregular 
band on each side, and farther down the sides golden; terminal seg- 
ment golden. Base of wings, scales and halteres yellowisli-white. 
Legs black. 
The male differs from the female in the front between the eyes be- 
ing about one-tliird as wide as in the latter, while she is rather the 
smaller. Length .22-.32 inch. 
The species agrees in most particulars with Harris’ description of 
Musca liarpyia in liis “ Correspondence,” and we are inclined to 
think that individuals of this species formed the subject of his de- 
scription. After comparing it with about a dozen specimens of Musca 
domestica received from Switzerland (through the kindness of Mr. S. 
II. Scudder), we cannot find that it differs in any respect from them- 
The golden color that Harris calls silvery, the reddish oval spot on 
the vertex, the black hairs on the thorax, are the same in specimens 
from America and Switzerland. Both also agree in the venation 
and form of the head and front. 
SUMMARY OF ITS HISTORY. 
The eggs are laid about one hundred and twenty in number, and 
in twenty-four hours the larvae are hatched. 
There are three stages of the larval state, and consequently two 
moults. 
The first stage lasts about one day (twenty-four hours). 
The second stage lasts about one day. 
The third stage lasts three or four days. 
The entire larval state averages from five to seven days. 
The pupal state lasts from five' to seven days. 
The period from the time of hatching to the exclusion of the im- 
ago lasts from ten to fourteen days in the month of August. 
Those larvae which were reared in too dry manure were nearly one- 
half smaller than those taken from the manure heap. For several 
days the larvae living in this dry manure did not grow sensibly. 
Too direct warmth, but more especially the want of moisture, and 1873.] 
149 
[Packard. 
consequently of available semi-liquid food seemed to cause tliem to 
become dwarfed. 
Parasite of Musca domestica. While no insect parasite has yet been 
hitherto found, so far as we are aware, in the House Fly, it is, in fact, 
preyed upon by a Coleopterous larva. In one puparium we discov- 
ered a large hole which had been eaten through the crust in the an- 
terior third of the body. Another puparium, on being opened, was 
found to contain the pupa of a beetle, of which Fig. 14 a is a dorsal, 
and Fig. 14 a ventral view. It is long and slender, with the abdomen 
unusually attenuate. Seen dorsally the prothorax is very broad, 
twice as broad and nearly concealing the head. The wings were 
free, not laid on the body; the anterior pair short and broad, the 
hinder pair much longer and narrower. The segments of the abdo- 
men are convex, each side giving rise to a hair. The abdomen grad- 
ually narrows, the terminal segment being lunate. From under each 
side of it extends a remarkably long and large appendage ending in 
a long bristle. 
Seen ventrally the fdiform ten-jointed antennae are widely inserted 
and diverge, extending along the front edge of the anterior wings, 
O’ O O O O' 
reaching a little beyond their middle. The hind tarsi extend to the 
middle of the abdomen. 
The two most interesting characters are the slenderness of the 
body, and the large long terminal abdominal appendages, which are 
rarely met with in Coleopterous pupae. From the sum of its charac- 
ters here given we should feel inclined at present to locate this re- 
markable pupa in the family of Dermestidae, with whose characters 
it agrees better than any other group of which we know the trans- 
formations. Of the vegetable parasites of the House Fly, of which 
there are several, we cannot now speak. 
EXFLANATION OF FLATE III. 
Fig. 1. Embryo of Musca domestica in an egg which has not been laid ovor 
twenty hours. Exochorion removed. 
Fig. 2. Embryo of Musca domestica still farther advanced, the egg having been 
laid about twenty-four hours; the exocliorion artificially removed, the embryo on 
the point of hatching. 
Fig. 3. Larva of Musca domestica just hatched; showing the distribution of 
the two main trachea; and the anterior and posterior commissures, (a, a) dorsal view. 
36, the same, showing the mode of origin of the pair of lower postero-median 
tracheal branches, seen from beneath. 
Fig. 4. Larva of Musca domestica in the second stage; sp, prothoracic spiracle; 
4a, head; at,antennas; mx, maxilla;; md, mandibles; 46, spiracles of Musca domes- Packard. ] 
150 
[Nov. 19, 
tira, divided into seven lot mbs. 4c, full grown larva of ftfusca domestica, showing 
the size of head relative to the prothoracic segment, with its spiracle, id, end of 
lobules of the spiracles, much enlarged. 
Fig. 5. Two anal spiracles of Musia domestica. ta, spiracle (much enlarged) 
of a younger larva than the subject of tig. 5, with a narrower peritreme, and the 
subet ntral dt) rrssion ncarer the centre of the spiracle. 
Fig. 6. Spiracl: s of Calliphora romitoria. 
Fig. 7. Spiracles of Sarcophaya carnaria. 
Fig. 8. Ventral view of puparium of Musca domestica. fa, dorsal view of same 
puparium; 86, prothoracic spiracles; 8c, end of body. 
Fig. 9. S] iraclts of j upnrium of Musca domestica. 
Fig. 10. Puparium (immature) of Stomorys calcitrans, dorsal view. 10a,the 
hinii’tventral view; 6, head-end enlarged; c, prothoracic spiracles. lOd, profile 
view of end of puparium of the same. 10c, anal spiracles of the same. 
Fig. 11. Pupa of Musca domestica. 11a, leg. 116, wing. 11c, optic ganglia. 
be, optic lobes, divided into two well marked divisions; oerj, upper oesophageal gan- 
glion, ri sting above the bass of the optic lobes; c, eye in ] rofile, and on the oppo- 
site side the unorganized mass of fat cells, out of which the optic fibres and cham- 
bers of the eye are to be developed, lid, antenna. 
Fig. 12. l’upa of St am or ys calcitrans, front view. 12a, dorsal view. 126, lateral 
view. 12c, head much enlarged; m, mandibl. s; mr, maxilla?; mp, maxillary palpi. 
Fig. 13. Thorax of semipupa of Stomorys calcitrans, dorsal view, showing the 
three thoracic segments, st, the prothoracic stigmata; w, wing; I, leg. 13a, ven- 
tral view of the same; 6, fore kg. 
Fig. 14. Pupa ] robably of one of the Dermcstidir, ventral view; b, dorsal view 
of the end of the body; c, ventral view; d, antenna. 14a, dorsal view of pupa. 
Found in Puparium of Musca domestica. PACKARD, TRANSFORMATIONS OF THE HOUSEFLY