Article beginning on page 253.
Psyche 6:253-257, 1891.

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Pysche, 1892, Vol 6.
Plate 7.
I




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CONCERNING THE "BLOOD-TISSUE" OF THE 1NSECTA.-111. BY WILLIAM MORTON WHEELER, WORCESTER, MASS. RHYNCHOTA. As representative of My observations on the oenocytes of the Phytophthires the just-born young
Zaitha fluminea are limited to a stage
of a wax-secreting Aphid, which in-
of the embryo immediately preceding
fests the alder, were studied. In sec- revolution. I find in the abdomen, just tions the whole body-cavity was found outside the appendages and stigmata, a to be filled with a reticulate fat-body, series of thickenings which foreshadow the nuclei of which measure only 3.5 å´* the compressed pleural rim of the larva The oenocytes are scattered here and
there throughout the reticulum appar-
ently without any definite arrangement.
he^ are large, brownish, opaque cells
with sharp contour. The cytoplasm
measures I 2-18 P ; the nucleus 5-
55 å´* They seem to have no morpho-
logical connection with the fat-body but to be merely slung in its meshes. The
nuclei stain deeply and present the typi- cal finely wound chromatin skein. Some
of the scattered cells were found in the three thoracic segments, whither they
had probably migrated during embry-
onic life from the pleural walls of the
abdomen. In the prothorax only two
oenocytes were found and these were
placed symmetrically one on either
side in the pleurae.
In the mature embryo
of Ramzfra
fusca oenocyte-clusters occur in five of the abdominal segments. They are
huge yellow cells with nuclei rich in
chromatin and are lodged in niche-like
depressions of the pleural hypodermis.
and imago.
The pair of these thicken-
ings in the first abdominal segment
develop excessively, bulging out con-
spicuously beyond the niveau of the
other thickenings, so that, had I not
observed that the pleuropodia are
invaginate in this form and did not their tufted secretion show clearly in the very same segment, I should have supposed
that I had found a pair of evaginate
knob-like appendages. Sections show
that the greater development of the
first pair of abdominal thickenings is
due to excessive proliferation of the
hypodermal cells to form a solid succu-
lent mass-the oenocytes. So many of
the hypodermal elements are here con-
verted into oenocytes, that only a few
flattened and attenuated cells remain to ' cover the mass externally.
From the
surface the oenocytes may be seen shin-
ing through this thin covering and this
heightens the resemblance of the two
swellings to the pleuropodia of such
forms as Blatta and Xiphidium. The




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254 PSYCHE. [April 189s.
pleural thickenings of the second ab-
nucleus deeply and of about the same
dominal segment are also more pro-
hue.
This reagent, of course, accentu-
nounced than those of the succeeding
ates the chromatic skein.
There are no
segments but much smaller than the nucleoli. first pair. I could not make out that
In some of the larvae all the oeno-
they gave rise to oenocytes. As I had cytes contain vacuoles. These are ar- no material of the later stages I was ranged in a broad band surrounding the prevented from following the develop- nucleus midway between the nuclear ment of these organs further. It is pos- and cytoplasmic walls. These vacuoles sible that there are in the adult several are but slightly refractive and are not pairs of oenocyte clusters as in other fat-globules. This condition of the insects and that they develop from be-
oenocytes was found
in a number of
fore backwards so that the stage which
larvae and, I believe, represents a nor- I studied may have shown only the mal physiological state. Wielowiejski formation of the first pair of anlagen. å has made a similar observation. One is
It seems to me more probable, how-
ever, that Zaitha develops only one
pair of clusters and that the others have atrophied to such an extent as no longer to appear during ontogeny.
NEUROPTERA. In the just-hatched
larvae of Stalls infumata a few oeno-
cytes were found as large clear cells
sticking in the pleural hypodermis be-
tween the insertions of the tergo-sternal muscles.
TRICHOPTERA. Specimens of the
larvae of an unidentified Phryganeid
were torn open in normal salt-solution
*and examined fresh or after treatment
with methyl-green osmo-acetic mix-
ture. In fresh preparations the gigantic oenocytes (Fig. I .) are yellow, more or less rounded, and often provided with
delicate processes which are attached to the tracheal hypodermis. The cyto-
plasm is usually finely granular; the
chromatic skein of the nucleus is dis-
tinctly discernible in the unstained cell. Methyl green stains both cytoplasm and
reminded of certain gland-cells which
store up vacuoles of a specific substance in their cytoplasm, preparatory to se-
cretion.
One of the facts brought out by
measurements of Xiphidium, viz : the
gradual growth of the oenocytes with
the growth of the insect, was again
clearly shown in the larvae of this
Phryganeid. Different stages gave the
following measurements.
Cytoplasm. Nucleus.
I. Larva just hatched,
12.0 p 4.6 p
2. Larva 13 mm. long, 40.8 p
15.6 p
3. Larva 17 mm. long,
62.8 p 20.3 p
4. Larva 25 mm. long,
103.7 p 29.5 p
5. ~m-va 3o mm. long, { :zz:i } {55. -}
74
Here the cytoplasm increases from
I 3. - 166.8 P, while the nucleus grows
from 4.6 - 74 p, so that the latter
undergoes a slightly greater relative
increase in size. In Xiphidium we
found the converse to hold good.
COLEOPTERA. The oenocytes of
Photuris $ennsylvanica (imago) are




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April 1892.1
PSYCHE.
of huge dimensions like those of the
Trichopteran described above ; their cy- toplasm measuring I I 8.5 - 185. v- across, while their nuclei range from 33.5-
60. p. The cells are disposed in loose
clusters in the pleural region of the ab- domen and resemble their l~omologues
in European Lampyrids.
In some Malacodermata Wielowiejski
distinguished three different varieties of oenocytes according to size. In the
Lampyrids he found only those of me-
dium size - corresponding to the sec-
ond variety of other Malacodermata, and
suggests that in the fire-flies the "kleine oenocyten" (third variety) may be
converted into the photogenetic organ.
It is clear that if the "kleine oenocy-
ten" are true oenocytes and if, more-
over, Wielowiejski's suggestion is well
founded, the photogenetic organs of the
Lampyridae must be ectodermal struct-
ures. If on the other hand these inter-
esting structures originate from the fat- body, as is usually maintained, they
must be mesodermal.
In Photuris $ennsylvanica the two
layers of the light-organ consist of cells which closely resemble the elements of
the fat-body proper. The cells consti-
tuting the inner layer have the same size and much the same appearance; their
nuclei do not differ from those of the
fat-body ; in the outer layer, which is
more especially concerned with the
photogenetic function, the cytoplasm is, of course, considerably altered, but the nuclei are indistinguishable in every
particular from those of the fat-cells.
The resemblance between the fat-body
and the light-organ is so great that I do not doubt their genetic relationship
though I have not studied the devel-
opment.
LEPIDOPTERA. Few insects appear
to be better adapted for tracing out the origin of the oenocytes than the Lepi-
doptera. This is especially true of the
larger Bombycid moths. That the seg-
mental cell-clusters arise by delamina-
tion from the ectoderm was conclu-
sively made out in the embryos of
Platysamia cec~o$ia and Telea poly-
@ems. Each cluster is several cell-
layers in thickne'ss and lies just behind and a little ventrad to an abdominal
stigma. The succulent cells constituting the cluster are at first polygonal from
mutual pressure, but as the time for
hatching approaches, they become
rounder and more loosely united. I
have not traced them through the larval
stages and merely record these frag-
mentary observations because they com-
pletely confirm Tichomiroff's and
Graber's observations on the origin of
the oenocytes from the ectoderm.
,
DIPTERA, Oenocytes probably occur
throughout this order. To the families
in which they were found by Wielo-
wiejski (Chironomidae, Tipulidae, Culi-
cidae, Tabanidae, Syrphidae, Muscidae,
Pupipara) I would add two others
(Cecidomyidae and Simulidae) .
In the larvae of Cecidomyia anten-
nariae beautiful large oenocytes occur
in nietameric clusters, each of which
consists of about five cells. . These
seem not to be so regularly arranged as
the oenocytes of Chironomus (Wielo-




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PSYCHE.
I April 1892.
wiejski) . One cell of each cluster is situ- ated at some distance from the others
but dorsad and not cephalad as in Chir-
onomus. The cells measure 45. - 75. p. ; their nuclei 1';;. a.
They are round or
slightly oval, and flattened in the same direction as the hypodermis, in niche-
like excavations of which they lie.
In the young pupa they lose their
connection with the hypodermis, be-
come spheroidal and vacuolated and
their nuclei decrease in size. 1 have
failed to find any traces of oenocytes in the mature pupa and imago.
In the larva of Simulia the oenocytes
resemble those of Cecidomyia.
The above insects belonging to many
of the natural orders were also studied
with a view to establishing the origin of the blood-corpuscles but my results were purely negative. I saw nothing to sup-
port Schaeffer's view* that the corpus-
cles arise from the fat-body. Such an
origin is improbable d priori inasmuch
as the cells composing the corpus ad-
iposum are specialized for storing up
fat and ~irates. That fat-globules and
urates in the blood-corpuscles do not
prove a genetic but only a physiological relationship between the fat-body and
the blood is obvious if we stop to ask the question : How do the fat and urate in-
clusions reach the fat-body ? It is most natural to suppose that they are trans-
ported thither by the blood-corpuscles.
That the reverse may frequently be the
case, viz : that the blood-phagocytes may *Beitrage zur histologic der insekten. 11, Ueber blut- bildungsheerde bei insectenlarven. Sprengel's 2001. Jahrb., 3 bd. heft 4. 1889.
receive their fat-globules from the fat- body and carry them to other parts of
the organism to be utilized in the meta- bolic processes which are continually
taking place, is, I admit, quite as
probable. But neither of these pro-
cesses throws any light on the origin of the blood-corpuscles themselves.
In the embryo the blood-corpuscles
probably arise from undifferentiated
mesodermic tissue. They are often
found in different stages of caryokinesis and I can see nothing improbable in the
supposition that they may continue to
multiply throughout postembryonic life.
It is also probable that n~esodermic cell- masses of an undifferentiated nature,
associated for obvious physiological
reasons with the fat-body, may function
as haematogenic centres during the
larval stages. For all his figures and
descriptions prove to the contrary,
Schaeffer's "blutbildungsheerde" may
be such undifferentiated mesoderm-
masses and not portions of the true fat- body at all.
In this connection I may mention a
very interesting organ which I have re-
cently found in embryos of Blatta and
Xiphidium and which appears to have
some physiological connection with the
other members of the '' blutgewebe."
This is a large v-shaped mass of cells
situated just beneath and attached to
the inner end of the oesophagus (stom-
odaeum) where the two entodermic
strands diverge. This cell mass lies
almost wholly in the trito-cerebral
(second antennary ?) segment and, I be-
lieve, represents a modification of the




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April 1897.1
PSYCHE.
greater portion of the mesoderm of
the segment, though this is difficult to decide. It is apparently the earliest
organ to differentiate from the walls of the coelomic sacs. Its cells, at first
wedge-shaped, gradually increase in
size, become rounded and highly vac-
uolated and resemble the fat-body ele-
ments, from which they may, neverthe-
less, always be distinguished by their
peculiar yellow tint. I have traced
the organ, which is a definite circum-
scribed structure, and which I call, for the present, the suboesopl~ageal body,
through the embryo into the larva,
where it disintegrates and finally
disappears. I regard it therefore, as
a truly embryonic and early larval
structure, quite distinct, at least physio- logically, from the fat-body. Its func-
tion is very doubtful. If the trito-cere- bra1 segment is homologous with the
second antennary segment of the Crus-
tacea and if, moreover, the suboesopha-
geal body really develops from the
mesoderm, it may be the homologue of
the " green-gland " and consequently
nephridial in its nature.
Reserving a general consideration of
the '' blood-tissue " for future publi-
cation, I here conclude with a brief
summary of the points brought out in
the foregoing paragraphs : -
([)
The fat-body of the Insecta is
derived from the mesoderm-being a dif-
ferentiation of portions of the coelomic walls and therefore metameric in
origin.
(2) The oenocytes are derived by
delamination or immigration from the
ectoderm, just caudad to the tracheal
involutions. They are also metameric
organs.
(3)
They are limited to the eight
trachigesous abdominal segments.
(4)
They appear to be restricted to
the Pterygota, in all the members of
which group they probably occur.
(5)
They give rise neither to the
fat-body nor to the blood but represent
organs mi generis.
(6) After their differentiation from
the primitive ectoderm they never di-
vide but gradually increase in size.
(7) The blood-corpuscles of these
insecta appear to arise early in em-
bryonic life and perhaps also in post-
embryonic life from undifferentiated
mesoderm cells. The evidence of the
derivation of the blood-corpuscles from
the fat-body as such is unsatisfactory.
(8) The suboesophageal body
arises in the trito-cerebral segment ap-- parently from the mesoderm. Though
it resembles the fat-body it must be re- garded as a distinct organ.
It disap-
pears during larval life.
Clark University, Dec. 22, 1891 .*
*Since the above article was written and sent to "Psyche," I have received two publications bearing on the origin of the fat-body in the insect embryo. The first is an account published in the second part of Kor- schelt and Heider's Lehrbuch der vergleichenden ent- wicklungsgeschichte der wirbellosen thiere, of Hey- mons' studies on Phyllodromia germanica. Soon after- wards Dr. Heymons kindly sent me a copy of his in- teresting paper (Die entwicklung- der weiblichen ges- chlechtsorgane von Phyllodromia (Blatta) germanica L. Zeitschr. f. wiss. ~051. LIII. 3.1891, p. 434-536) the lucid illustrations of which show essentially the same method of origin for the fat-body as fig. 3 in my plate. He finds, also, that other portions of the coelomic wall may contribute to the formation of thecorpus adiposum.)



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258 PSYCHE. [April 1892.
,
Fig. I. Cluster of oenocytes from a
nearly mature Phryganeid larva, o,
oenocytes ; /, large tracheal branch ; ft, smaller tracheal ramifications ; h, tra- cheal hypodermis.
Fig. 2. A nearly mature embryo of
Xiphidium ensz~erum. 00, oenocyte
clusters seen from the surface through
the integument ; a, pleuropodium of the
right side (appendage of the first ab-
dominal segment) ; s, styli (belonging
to the ninth abdominal segment; the
specimen being a male) ; c, cerci.
Fig. 3. Part of a transverse section
through the first abdominal segment of
a young embryo of Blatta ( Phy/Zodro-
mia) germanica. b, pleural ectoderm ;
0, oenocytes ; a, pleuropodium ; i, coel- omic cavity ; a, entoderm ; w, nerve-
cord ; e, fat-body ; 6, blood-corpuscle ; d, diverticulum of the coelomic wall,
which in appendage-bearing segments
becomes converted into the limb-muscu-
lature but in this segment atrophies.
Fig. 4. Part of a transverse section
through one of the abdominal segments
of a Plasturus nymph ; o, oenocytes;
hk, hypodermal cells; Y, chitinous cu-
ticle ; ee, fat-body ; 66, blood-corpus- cles ; w, tergo-sternal muscles ; E,
muscles in cross-section.
TACHINID PARASITE OF
EUCATERVA VARIARIA GROTE, AND
OTHER NOTES.
BY C. II. TYLER TOWNSEND, LAS CRUCES, N. MEX. Along the arroyos on the mesa-lands,
and near the bases of mountain ranges,
in southern New Mexico, may be found
growing large tree-like shrubs, with
willow-like leaves, and bearing in spring numbers of rather large pink flowers,
which are followed by catalpa-like seed- pods.
This is known to botanists as
Chilopsis suZigna.* In August these
shrubs are well stocked with the co-
coons of a moth, Eucaterva variariu
Grote, the larvae of which feed upon
the leaves. The identification was made
by Dr. Henry Skinner, to whom I sent
a specimen of the moth. The cocoons
are very lightly spun of silk, binding
*I am indebted to Professor E. 0. Wooton, of the New Mexico Agricultural College, for the name.