Daily Yellowstone journal., 1890-01-21
I'M OF INSECTS.
- Insect by Which Alone
F, iI,,lueed L. the Ilorux.

'A''l ''lflti 'littT-
tain d. 'IU.r giI!f lrn :,
sect, .H,t,, Iac gadlly and nyr, dur
ing thar ,.'gat. arises from the vibra.
ton or RAPID motion of tlicir wings.
Such a ~suppasj;lon is extremely plaus.
ible at first sight. We see the animal
moving through the air; we know
that the wings are in a state of rapid
motion: aud we also know that il is
natural for "A body rapidly vibrating
in the atmosphere 10 cause "A sound.
We put all these facts together, and
We conclude that the phenomenon is
explained when we attribute the
sound 10 the rapid waving of the
wings. But, like many other hypoth-
eses which owe their origin to the evil
Gence of the senses alone, this appears
TO be erroneous. The subject has been
investigated with much ingenuity. and
the conclusion arrived at is very diff.
fcrent from the common belief. We
shall present n brief outline of the re.
searches. They are not only interest
ing in themselves, but afford a good
example of the manner in which sci
eutitic Investigations are pursued.
1t has been found that the wings
have no part in the formation of the
sound, for the hum of the insect con.
tinucs eve when its wings are entire
ly cut away. There is, however, a
different pitch of the sound, and it
las been a,ecrtaincG that the more of
the wing there is taken away the
higher this becomes. The sound which
the insect emits is susceptible of con-
siderable variations. 1t may be that
it maintains an equality of pitch and
strength during Il uniform motion Of
the wings, for SO IN fact it appears:
but every change in the velocity of
the flight, every disturbance of the or.
binary motion, generally causes also
an alteration in the tone. An idea of
the origin Of the tone is, however,
only Ia he obtained when the insect is
held by the legs, and excited by pres.
sur or other means to 90 through all
its motions Of the wing, and thus 10
produce "A sound. Ii has been found
in this manne that the tone of the
common gadfy varied as the effort 10
eXtrlcate itself was put forth with
greatero or less energy.
That parto of the insectby which alone
the sound is produced is the breast or
thorax. lntwo-wingedin insects thiscon-
sists simply OF a cavity covered by a
thin membrane. which exhibits on its
surface various elevations and depres.
sions, but is, nevertheless, perfectly
continuous. To this hollow ease are
attached different sets of muscles,
which serve for the motion of the
legs and wings. and are capable Of
contracting the cavity in various di.
rcctions. In this cavity Of the insects
tboraX there are two very small holes,
which let air out or in by the follow
ing process: When the wings rise and
fall, as in flying, the cavity is alter.
nately contracted or expanded, the re-
suit of a peculiar mechanism on which
the motion is dependent. Now it is
clear that the contraction must drive
out a partof the air, just as II piperey.
pels the air from the bag of his instru
ment by pressing his arm against it.
On the other hand, when the cavity
Of the insect Is expanded by an opPo-
site motion Of the wing. an equal
quantity Of air ruslles through the air
holes. There is, therefore, connected
with the uotiou of the wings a con-
slant proportiOnally rapid and intense
breathing, and this breathing is the
true cause of the sound. 1t is the eff
iluX and the influx of the air which
produces the buzz or hum which we
hear, just as the current of air draws
music from the Eolian harp When
forced at short intervals through the
small holes Of the soundboard, or, TO
take a more familiar example, By a
mechanism similar 10 that of the
mouth in whistling. The sound Of the
Eolian harp bears a remarkable ne.
semblance 10 that of many insects.
Now, it is evident that this theory
can be proved or d~isprovcd in a very
simple and satisfactory manner
namely, by closing up the air holes Of
the thoax Of the insect, without in
juring il in any other way. This was
done, and the flight Of the gadiiy was
then found TO be accompanied by no
sound whatever. II is true that tho
insect dies of suffocation soon after
such an experiment, but not directly,
because there are air holes situated
lower down, in the abdomen of the
animal, and through these respiration
is continued for a short time. But
they emit no sound during the flight
Of the insect, for they are then totally
inactive. The insect breathes from
the air holes Of the abdominal part
when ii sits and crawls, but through
the air holes Of the thorax when ON
the wing. According to this view,
the hum of insects is in reality a
whistle. New York Ledger.