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Psyche 4:305-309, 1883.

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July-September 1885.1 ~s2‰Û÷X%T
THE LARVAE OF OESTRIDAE.
BY FRIEDRICH BRAVER, VIENNA, AUSTRIA.
[Translated by B : Pickman Mann from Friedrich Brauer's "Monog-raphie der oestriden," Wien, 1863, p. 35-40.] The larvae of the oestndae, although
in many cases quite peculiarly shaped,
are so nearly related to the larvae of
the rest of the muscidae-calyftera
that it has not yet been possible to dis- cover for them a constant distinguish-
ing character founded upon their struc-
ture. The reason of this lies in part
in the oestrid larvae themselves, since
they are very different among thein-
selves, and in part also in our defective knowledge of the muscid larvae.
At present, it is true, no real muscid
larvae are known with large thorn-
warts,-as I will call the dermal for-
mations which occur in many oestrid
larvae, which are conical, soft at the
base, fleshy, and corneous at the tip,-
also none with the characteristic stig-
matal plate of the Gastrophilus lar-
vae ; on the other hand very many are
known with thorns, like those of Der-
matobia, or naked, like those of the
young Hytoderma, or with horny
stigmata1 plates, like those of Cephe-
nomyia. The remarkable parasitic
method of life in mammals can prob-
ably be looked upon as peculiar to the
oestridae. I leave it therefore to a
future observer to establish a character for the oestrid larvae whereby they
may be distinguished from all other
muscid larvae, and limit myself here
to the description of the larvae accord- ing to genera and species.
The oestrid larvae belong to the
great division of those dipterous mag-
gots which have been called headless,
since they are segmented throughout
and the usual regions of the insect body are not separated. Only a cephalic
and an anal end, therefore, can be dis-
tinguished on the annulate body of such
larvae. In general the following com-
mon characters and peculiarities of the
oestrid larvae can be specified.
I.
The body of all oestrid larvae is
really composed of twelve rings.
The
first two are however not always dis-
tinctly separated, so that I take them
together in the description, and desig-
nate them both by the name of cephalic
ring, on which in many cases an an-
terior and posterior section is clearly
to be distinguished. On that account I
assume only eleven segments, as earlier
authors have done. Only the new-
born larvae of Gastrophilus make an
exception to this number; they, if
Joly's statement is correct, possessing
thirteen segments.
2. Two anterior, external breathing-
organs are always to be distinguished
on the larvae, between the first and
second segments of the body, and two
posterior, external breathing-organs on




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PSYCHE.
[ July-September 1885.
the last ring. The former are very
small and appear either as points,
knobs or fissures, or the anterior ends
of the tracheae are hidden entirely in
a cylindrical invagination of the skin
( Gast?*o$hi/z~s). The posterior breath- ing-organs are either breathing-tubes
which are protrusile and retractile
(new-born GastropJzilus [p. 361 larvae
and Cephenomyia larvae), or large
stigmatal plates which are constructed
according to two kinds of types. One
of these types is represented in Gastro- $hiZus and Dematobia, the other in
the rest of the genera. The stigmatal
plates are more 01- less protected by
lip-like organs on the last ring or by
withdrawal into the preceding ring,
and are in this way cleaned from sub-
stances which adhere to them.
I have described in detail under that
qenus the structure of the posterior
stigmatal plates in Gastro/hiZus. The
majority of the genera possess how-
ever two stigrnatal plates in a real sense, consisting of corneous chitinous sub-
stance on the last ring. Each ring is
usually crescent-shaped or reniform, in
younger larvae even quite circular, and
appears when magnified either as lat-
ticed with coarse meshes, finely porous
or almost snlooth, sometimes radially
furrowed. On the inner border of each
plate is in all larvae in the third and
in many in the second stage a thinner,
membranous or knob-like place super-
posed or imbedded, sometimes enclosed
in the plate itself. The attachment of
the trachea coi-responds to this place on the inside. Since it usually has the
appearance of an opening, and also has
been taken for
such, I call it the false
stigmatal opening. It has not yet been
ascertained without doubt that breath-
ing goes on in such stigmatal plates, but it probably takes place through pores of the plate. It seems to me as if the
plates were penetrable especially at the circumference of the attachment of the
tracheae.
3.
The new-born larvae all possess
external mouth-parts ; in the later
stages larvae with oral hooks and those
without them are to be distinguished.
An internal pharyngeal framework of
various development always occurs ;
this encloses the membranous gullet
and by its muscular structure is of es-
sential service in the sucking of the
larva. If oral hooks are present, they
are connected with this by a joint.
Usually a U-shaped, bent chitinous
plate is to be seen, whose open side
looks upward ; from the side it has the
shape of a sitting butterfly whose large upper wing reaches far back and has
the smaller, narrow under wing under
it. Since the wings of the two sides
are grown together firmly underneath,
the whole pharyngeal framework ap-
pears like a flying insect, when the
wings are bent apart from above, and
with the base in a plane. The part
lying more or less in front, which is to be found in the middle between the
wings, and which really radiates out
into these, or is united with them like a ligament, is what Schroeder van cler
Kolk calls the tongue-bone.
In the pharyngeal framework there-




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July-September 1885.1 ~ s c ~ . 307
fore there can be recognized a body
(Schi-oeder's tongue-bone) and four
wing-like processes which often again
consist of several parts. The body is
connected with the wings posteriorly.
It is always bent in a U-shape, and so
that the open end looks upward, i.e.,
if other soft parts of its vicinity which also close this are disregarded. [p. 371 Bent flat, it shows a more or less dis-
tinctly H-shaped chitinous plate, with
very broad side parts, which-in full-
grown larvae-become confluent behind
into a simple, broad plate, and only
leave an oval hole in front of them for
the passage of the discharge duct of the salivary glands, but posteriorly bear the four wing-shaped processes (two large
upper, or in the outspread plate outer
ones, and two smaller slenderer in-
ferior or inner). On the anterior end
of the body, in many genera, oral h001i~ are jointed to the short anterior side
parts. Tn the anterior curved excava-
tion of this lies in the n~embranous ex- pansion a small corneous chitinous plate which is pierced like a sieve and whose
nature has not yet been more closely
investigated.
It seems to me as if this
plate lay at the outlet of the salivary
ducts. It is especially distinct in Ce@e- nomyia larvae. It is wanting in sev-
eral others.
In young larvae the pharyngeal
framework consists only of two chiti-
nous rods which are united in front by
a chitinous band ;these chitinous rods
radiate out behind in little wings. A
(similar) pharyngeal framework occurs
in all other muscid larvae, and corres-
ponds in the perfect insect to the chiti- nous frame of the proboscis. I have
repeatedly convinced my self that such
is really the case, since I have opened
the coarctate pupae of Cephenomyia
and Gast~ofhiZus before the emergence
of the flies. Since in these genera, as
we will see later, the nymph is tightly
enclosed by the puparium, it can be
noticed how the already freed pharyn-
geal framework, which remains at-
tached to the puparium, rests in the
mouth-fissure of the nymph, and is
drawn out of it as soon as the nynlph
is taken away or the lower lid is lifted off. It is also easy to form an idea that the pharyngeal framework together with
its internal parts corresponds to the
proboscis of the fly if it is observed
how other m~~scid or syrphid larvae
while alive project and withdraw this
exactly as the fly does its proboscis.
In Hypoderma the month-parts un-
dergo a retrograde metamorphosis from
the second stage (after the first molt) ; the oral hooks disappear, and therewith
all the external mouth-parts, but the in- ternal pharyngeal framework remains.
4.
The oestrid larvae show antennae
(at least rudimentary ones) above the
mouth-parts ; these have the appear-
ance of corneous or usually membranous
knobs, and in the latter case are pro-
vided with one or two ocelli-like points. Subulate, many-jointed antennae, such
as occur in many muscid larvae, are
never found.
5. All possess an anus, which lies
on the last ring, under the stigmata1
plates, and is very small.




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308 PSY CHB. 1 July-Seplember I%<.
6. They molt twice while they are 7. This pupation must be consid- parasitic. I have observed most closely
ered as a third molting, in which, how-
the molting in Hypoderma larvae of the
ever, the skin is only detached around
second stage. In ff. diana the pas-
the pupa, but is not stripped off, and
sage from -this stage [p. 383 to the remains in connection with it by means last one takes place about the begin-
of four tracheae. Tile hardened larval
ning of February. If in a cutaneous skin, or puparium, is bsirst open at the muscle which is richly larded with cephalic end by the emerging fly by such larvae the capsules of those larvae means of the frontal bbdder filled with whose hinder stigmata1 plates have the fluid, in the direction of the arcuate . shape of the third stage, but are still sutures ina double manner. Although clear yellowish-brown, are carefully the pupation resembles herein that of slit open, the skin characteristic of the the muscidae in general, yet there oc- preceding stage, with the many little curs in one part of the oestridae, i.~, thorns heaped in groups, will be found in Hypoderma, it peculiarity which has either still partly attached to the front not been observed before, namely, that end of the larva or entirely dependent the larva transforms in the puparium from the cephalic end or folded together in a completely outstretched. condition, along the dorsal side.
The process of and this therefore is far larger than the molting seems to be entirely similftr to insect which comes forth from it. that in the Melophagas larvae ; at least 8. So far as they have been observed,
Leuckart states that the old skin in
they lead a parasitic life in mammals,
these is shoved together toward
the
and feed upon the juices of "these mi-
cephalic end of the larvae and there re- male. In flypodem a blood-red in-
mains attached. The Hypoderma larva,
testine often shows through, and it is
immediately after the molt, is pure likely that these sometimes suck up white, very soft, and appears naked, blood in addition to the exudation which since the thorns do not become dark immediately surrounds them. and distinctly separated from their sur- 9. The closely observed larvae all roundings until they harden. show at first a slow and finally a rapid Three forms or stages are to be ilk- development, so that there occurs a tinguished, corresponding to the molts, resting stage which often lasts seven which forms in ~~~~~~~, G~~tro- months, between the swarming of tile $hilus and Dermatohia show great imago and the first visible appearance differences. In the third stage the lar- of the larvae. vae reach their full size, usually change The tarvae of the oestridae were for-
their color and that often very consid-
merly divided into two groups : into lar- erably, and then first leave their host- vae with oral hooks and those without animal, crawl away and pupate, after
external mouth-parts. Such a separa-
the manner of the muscidae. tion is of service in distinguishing the



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full-grown larvae, but scientifically un- natural ancl incorrect, since in the first place this peculiarity of the full-grown larvae corresponds to no similar degree
of relationship of the perfect insects,
and in the second place it is only tern- porary, {p. 391 since all oestrid larvae possess oral hooks when they are quite
young. Such a division also as Clark
attempted to make, into*cav/coZae, cuti- colae, and gastrico?m, is inadequate,
for while the species of a germs do in-
deed always agree in life-history so far as their occurrence as parasites in a de- terminate organ is concerned, neverthe-
less the larvae of very different genera may also share this same manner of
life with others ; for instance, Hyfo-
de?vna, Cutereh-a, De~matobia, among
which there is far more difference be-
tween I and 2 than between Cuterebra
and Cefthenomyia, if the imagines are
considered. Such a division is there-
fore likewise not a natural one, since it disturbs the natural relations of affinity. Two elements must be considered, in
order to bring about an approximately
natural division : in the first place the organization of the larvae, and in the
second place their manner of life ; ancl the latter in a subordinate degree,
though this is here more important
than in other animals, since as yet there is no example of two species of oestri-
dae of one genus having been found
parasitic in different systems of organs. Thus the Ce$he~omyia larvae belong
to the oesophagus, the Ce$haZomyia
and Oestrus larvae to the nasal and
frontal cavity, those of Gastrofhilus
to the intestinal tract, and those of Hy- 'poderma to the subcutic~~lai- cellular
tissue. '
Although it is stated that the larva
of Gastro$hiZz~s has been found in the
oesophagus, this is one of the excep-
tional cases which are not authenticated. Of course only the full-grown larva is
meant here, since young larvae may
always be found in other places during
the immigrations. So for instance the
young' Oestrus and Ce$hevzomyia lar-
vae both immigrate in like manner
through the nose, and their roads do
not separate until they get there. but
the former migrate into the frontal
cavity. and the latter into the oesoplia- geal cavity.
Of the organs in which oestridae
occur, the skin, or really the subcu-
titular cellular tissue, is that which is the most strongly attacked ; the larvae
of four genera : Hypoha, Oestro-
myiq Dermatobia, Cuterebra, live in
it. The nasal and frontal cavity are
inhabited by the genera Cefhalomyia
and Oesh-us, the nasal and oesophageal
cavity by the genus Ce$henomyia, the
intestinal canal by the genus Gastro-
$hiZus. The transformations of the
other genera of oestridae are unknown.
It is interesting farther that many
genera occur only as parasites of certain families of mammals, while others have
a somewhat wider or very wide range
of distribution, and so have for hosts
the different mammals, yet not quite
without choice, and often even seek
men for their breeding places.
Thus until now the larvae of Cephe-




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nomyia have only been found in the
be relied upon for an inference, since
throats of cervina, those of the genera
Oestrus le#orinus belongs to the group
Cephalomyia and Oestrus only in iylo-
of oestridae with naked bristle, but its foda and cavicornia, those of the larva lives upon a rodent. It is seen genus Gastruphilus in soIidungula that such divisions are only artificial and multungula (Rhinocervs} , but and serve for orientation, but that ffyfoderma, on the other hand, in nevertheless nature cannot be forced caviwrnia (Bus, Cajra, Antilope), into them. Such divisions are there- cervina ( Cervus, MoscJius), and fore only temporary, and only too eyui&, CdereSra larvae in rodentia often become witrue so soon as new and -fnars@iala, and finally those of discoveries are published. It is there-
Dermatobia in (logs, oxen, horses, and fore best to treat of the larvae accord-
even upon man.
ing to their genera, and to limit these
[p. 4.01 Another picture is formed
as naturally as possible, since it has
if the perfect insects are divided accord- thus far been found constantly in this ing to a peculiar character into those
family that the larvae of one genus all
with pectinate antennal bristles ( Cute- have a like life-history, and conversely reira, Dermatoita), and those with
the generic characters of the imagines
naked antennal bristles (Hyfoderma,
can scarcely lead us astray if we wish
Gustropkil~ Cepkenomyia, Cefhalo-
to draw an inference as to the life-
my's), since the larvae of the former
history of a larva perhaps not yet inves- are parasitic in ungulate animals as well tigated.
In the case of a new genus,
as especially in rodeniia and maw-
however, we can infer its life-history
pluiia, but those of the latter only in
with very little certainty. Experience
wngulata. This hitherto so convenient alone teaches this. and practical division likewise cannot
WAXY SECRETIONS OF PSYLUB LARVAE.
Dr. FranzUw, in his t'BeitrSge zur kenntniss der jugendstadien der psyll iden" (Verhandl. K.-k.zool.-bot gesetls., i8S4, v. 34; Abh.), p. 144, thus describes a curious secretion in the larvae of PsylZu dmi: "From wax-glands
surrounding the anus the larva emits a white secretion, which a'ppeai-B as a hollow, venni- form thread that allows the paesage through it of the fluid excrement of the larva. This white thread, which reveals the presence ofthe larvae hidden in the axils of the leaves behind the stipules, elongates continously, but breaks off repeatedly on account of itsown weight and consequently reaches no very considerable length. Furthermore this larva secretes from the wax-glands on the dorsal surface of the last abdominal segment extremely fine white threads, which form unitedly a very loose, light flock." The larvae of Triasa, three spe- cies of which larvae are described in the same paper, have their entire outer margin sur- rounded by hyaline, silky, very fine, threads of wax, which lie close to one another, and seem to form a short, closely-trimmed fringe around them,




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