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Psyche 4:110-111, 1883.

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-precious systematic part of the Entomo- logical department. When will our
National museum fully warrant its name
by becoming the one legitimate and
most satisfactory repository of all such collections in whatever branch of sci-
ence ?
In closing this brief notice of one
whose personal relations and whose ap-
preciative and instructive correspon-
dence with the writer during the past
fifteen years will ever remain a green
and pleasant memory, we would empha-
size the fact that his writings throughout breathe a calm and judicial spirit, void of personality. The only instance that
occurs to us where he gave expression
to ruffled feeling is in the '*Synopsis of the coleopterous insects of the group
cleridae which inhabit the United
States" (Annals lyceum nat. hist. N.Y.,
April 1849, v. 5, p 9-35). In the
prelude to this paper he indulges in
some severe reflections on the exclusive attitude of the Latin or South European
countries toward the scientists of other countries. more particularly as exem-
plified by Spinola's work-reflections
not altogether unwarranted even at the
present time.
GILLS OF INSECT-LARVAE.
BY GEORGE MACLOSKIE, PRINCETON, N. J.
The gills of aquatic larvae of insects
consist of elastic sacs arising as out-
growths of the epidermis and enclosing
a system of fine branches from the air-
tubes or tracheae, being thus pneumatic
branchiae. They vary greatly in the
number of the sacs, in the number and
complexity of the enclosed air-tubes,
and in their position. In the elmidue
(of coleoptera) they are simple and
are distributed ventrally on the abdo-
men ; in Ephemera (of neuroptera) they
are also simple, and extend from the
sides of the abdomen ; sometimes they
are caudal appendages, and in the
libellulidae, or dragon-flies, they be-
come complex, having in some cases
many sac-like lamellae, and many hun-
dreds of branches in each, the whole
structure planted within the rectum,
from the walls of which the lamellar
sacs open like so many pockets.
These structures have been described
by R6aum~ir, L6on Dufour, Audouin,
Oustalet,l and many others. Oi~r'pres-
ent purpose is to rectify an error in
their anatomy, as usually represented,
which has important bearings on other
questions.
It is usual to describe the laminae of
the pneumatic gills as containing sys-
terns of fine tracheal loops, somewhat
after the pattern of a plurality of carbon- wicks in an Edison lamp. Uastalet
says, for example, in the Amales des
sciences mturelles (1869, s. 5, v. I I), that the branchial laminae "include a
veritable chevelu of tracheae folded on
themselves so as never to reach the
extremity of the fingers of the glove ;" and that they serve as a loose sheath
1 Ann. des sci. nat., Zool., 1852, s. 3, v. 1';; 1862, s. 4, v. 17; 1869, s. 5, v. 11; 1872, s. 5, v. 16.



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November-December 1883.1 F'S2TH.B. 111
for a tracheal arbuscle (shrubbery)
whose last ramifications are not only
recurved but anastomosed so as to
com-
plete the circuit ((t $Zeh canal), thus
forming' veritable arches (arises). His
figure agrees with his descriptive repre- sentation, showing the very numerous
ultimate branches of the tracheae as
completely arched, and his idea evi-
dently was that there is a capillary cir- culation of air in the tracheal tubules
like the capillary circulation of blood
in the gills of fishes.
-
Chun2 correctly shows that the rectal
branchiae of LibeZZuZa are outgrowths
of the [hind] intestine, having at their extremity no epithelial cells, but only
the intima (or cuticle) enclosing the
tracheal filaments. The epithelium
gradually grows thinner from the base
towards the extremity of the branchial
laminae, and at length disappears, being afterwards represented only by the cnti- cle. The tracheae divide dicl~oto-
mo~~sly, finally becoming capillary air- tubes, which this author also (being
here inaccurate) supposes to reunite
again into stronger stems. This part
of his plate is so confused that one
cannot make out whether the branches
reunite again or not, and we presume
that he did not try to follow them to
their extremities.
In a specimen of these branchial
laminae which we rolled under the
cover-glass, we found that the multi-
tude of tracheal ramifications ended
2 CHUN, Carl.
Ueber den bau, die entwickelung und
p!~ysiologische bedeutung der rectaldriisen bei den insekten. Inaugural-dissertation. . , . Frankfurt a. M., 187.5.
caecally ; all were of about the same
length, their extremities recurved with- in the containing sac, and their tips not at all swollen, but rounded oft'. Thus
if they were stretched out they would
form a brush like the hairs of a horse's tail.
As they are elastic and the enclos-
ing sac is distensible, we think it highly probable that with each water-inspira-
tion the sacs enlarge and the tracheal
spray (having air forced in by the
forward
compression of the large tra-
cheae) spreads out so as to bring the
full tide of air close to the tide of water. L6on Dufour seems to have had some
process like this in view when he said
that each lamella of the branchia of
Potamo/hiZ~~s is "probably swollen
during' life by air transmitted by endos- n~osis." As we understand the case, the
air is injected into the branchiae from the rest of the body by rhythmical contrac-
tions, and its gases then communicate
endosmotically with those in the tidal
water, so as to secure renovation.
The paper by N. and E. Joly on the
larva of Prosofistoma^ confirms our
observation. This larva was supposed
by Latreille, Dnm&il and Milne-Ed-
wards to be a branchiopod crustacean,
and is so described in Milne-Edwards'
Histoire des crustac&s (v. 3, p. 558).
But MM. Joly found out that it was
the larva of a coleopterous in~ect,~ and they figure and describe its external
-- -
July, N. and E. Etudes sur le prktendu crustack au sujet duquel Latreille a cr66 le genre prosopistoma, et qui n'est autre chose qu'un veritable insecte hempode. (Ann. des sci. nat., Zool., 1872, s. 5, t. 16, no. 7, p. 1-16, PI. 13.)
4 It is in fact one of the ephemeridae.,



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-112 PSYCHE. [~ovember-~ecember 188~.
tracheal bfanchiae, showing that the
branches of the tracheae end caecally.
In this case the branches are so few that their terminations can be easily made
out.
The importance of this anatomical
item depends on its bearing on the
functions of the whole tracheal system.
The action of the tracheae is tidal
rather than by peripheral capillary
circulation. Here also the endings of
the ramifications are found to harmon-
ize with their internal terminations
along the nervous and digestive tracts,
and in other parts of the tissues which
they supply. We never find a double
system of tracheae with capillary rami-
fications interposed for the transmission of air from one system to the other. It
is not easy, in the living insect, to
determine the ebb and flow directly ;
as the movements occur suddenly, have
their speed multiplied by the degree of
microscopic amplification ; and hence
we are able only to see the rhythmical
peristaltic action, and are left to guess at its cause. We find, however, the
muscular contractions and expansions
of other parts of the body synchroniz-
ing' with the pulsations in the gills, and thus explaining how the flux and reflux, rather than a mere circulation of the
air, is the cause of its renewal.
Princetoz, N. J., 12 Dec. 1883.
THE SCREW-WORM FLY, COMPSOMTIA MACELLARIA. BY SAMUEL WENDELL WILLISTON, NEW HAVEN, CONN. IN connection with Professor Snow's
article on this fly it seems worth while to give a brief synopsis of papers pub-
lished in the past few years by the able dipterologist of South America, Dr. E.
L. Ari-ibhlzaga, of Buenos Aires. From
his studies he has ascertained no less than twenty-six different specific names that this fly had received ! It is possible
that some of these names would apply to
distinct species 'were their types exam- ined, but it is a thankless task to encleav- or to make order out of the chaos in
which Walker, Macqnart, and obi-
neau-Desvoicly have involved the subject, and the result of Arribhlzaga7s thorough studies can with propriety be adopted.
Psyche, Mar.-Apr. 1883, v. 4, p. 27-30.
To these results, however, Mr. J. Bigot, of Paris, has recently taken exception,
in a note on Professor Snow's paper.
This author's penchant for making syn-
onyms himself may perhaps have
something to do with his wishing to
preserve species founded on inade-
quate grounds. His argument that "il
me semble fort hasarcleux d'avancer
qii'un seule et 7nhe espdce se
retrouve, en permanence, depuis les
confins de la Patagonie jusqu'au clelsl
des provinces centrales cle 17Am6rique
du Nord, vivant indifl4remment sous
les zones torrides, temp6rkes et mhe
froicles? " is of little value, when the Bull. soc. entom. ~rance, 12 Sept. 1883, no. 17, p. 154-155.




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