South Bend news-times. (South Bend, Ind.) 1913-1938, 1917-11-23
Chasing Flies Win
Blue Lights
BY GARRETT p. sERvIss.

colored lights. II a room is filled
with blue light flies will escape from
it If they can. and. If not able TO
escape, will settle down and keep
quiet If a window is left open they
will hurry OFT into the daylight.
If blue and green window panes
are interspersed with a number of
red and yellow ones the effect up
on the flies is nearly the same as
when blue light alone is used.
A shaft of white light passing
through the room becomes a trap
for them, and they will follow it
out Of doors.
The explanation, according to the
French investigators, is that the
eye of the fly is virtually blind to
the blue and green rays Of the
spectrum, partially so TO the red
and less 10 the yellow rays. Only
the full com bination of rays. giving
white light, forms a satisfactory il
Elimination for the fly The blue and
blue green not only fail 70 give light
to the insect, but they even appear
TO have a repellant effect upon IT,
Like Red to a Bull.
This suggests an easy method of
keeping flies from such places as
hospitals and all rooms where
white light is not imperatively need
ed by the human occupants. Food
in restaurants and store-rooms may
be protected from flies by illuminat-
ing il solely with blue light II is,
it appears, not merely the sense of
gloom that drives out the flies when
a way of escape is placed before
them, but the repellant effect OF the
shorter and quicker waves of light
1t is not the color as such that has
this effect, but il is the increased
frequency with which the shorter
waves strike the eyes Of the fly.
1t is probable that the fly, if it
perceives any colors at all and if it
could describe those colors, would
chromatic scale of ours. Red. yell
low. green, blue, etc, are simply
human visual sensations which may
not be shared by any animal other
than man.
If we could see the red flag that
excites such ungovernable fury in
a bull through the bulls eyes we
might get either no color impress
sion at all or or else some indescrib-
able one, not included in our spec
trail range and never imagined by
us as possible.
Irritates Nerves.
The example OF the fly, however,
suggests that the infuriatine effect
Of red upon the bull is due to some
nervous irritation, not Of the nature
OF color sensation, but more re-
sembling the effects of discordant
sounds upon the ear, and arising
from the peculiar frequency and
force OF the impacts of the red
waves.
Undoubtedly it would have been
possible for our nervous machinery
10 be so arranged that we should
have heard with our eyes instead of
with our ears, and by means Of the
waves Of the ether instead OF those
in the atmosphere. The functions
Of sight and hearing might con-
ceivably have been combined in the
same sense organ, and who can say
but that this NAV really be the case
with flies and other animals which
possess no ears.
II the effect Of blue light on the
fly is equivalent to that Of a men
acing sound on our ears. il is no
wonder that he fees from II If he
can and lies very low and still if
he can't cet away.
Senses of Animals.
It is true that ears, as we know
them in the animal kingdom. are
only made TO respond to the rela-
lively heavy blows Of the atmos-
pheric waves. but, nevertheless, the
inner auditory mechanism is so deli
cate as to defy all attempts to make
n final analysis of il. and there are
many creatures which possess senses
unbestowed upon us, that enable
them 10 obtain impressions from |
their surroundings which surp~ss
our understanding.
The wonderful similarity OF the
gamut Of sound with that of light I
udS tlltN DttU DOlUleQ Oul. NOuUu I
and light are like two fiddles play /
ed in different keys, one of them
nearly so octaves above the other. /
The practical limits OF musical /
sounds lie, according 10 Tyndall, /
between 40 and 1000 vibrations per
second. If we take 100 for the fun
damental tone of the lowest octave, !
the fifth octave above will have g.
200 vibrations.
The limits OF vision lie between
about 42O million-million and 74O
million-million vibrations per sec
ond
In the first case the vibrations
are produced in the air. and in the |
second they are supposed TO be 1
produced in what we call the ether !
but in each case il is a peculia- |
nervous apparatus terminating in |
the brain which enables us TO re-
ceive an effect from the vibrations I
and in each the quality OF that /
effect varies with the frequency Of |
the vibrations. while in both the (
variation Of effect is similar in its
character.
Flies Like Lellow.