The morning news. [volume] (Savannah, Ga.) 1887-1900, 1897-10-10
How Flies walk on the Ceiling.

FROM the l4lleTay Digest.
In old text books we were told that flies
are enabled to walk on the ceiling by
means of suckers" on their feet a state
ment that might have been disproved by
any one who took the trouble to glance
at a ffy's foot through microscope. This.
and some later explanations of what is.
after all, still something of a mystery, are
discussed by C, II. Dierhold in our Ami
NAL Friends (september). We quote his
article below:
1T is a curious fact how our under
standing Of many common and apparent
ly simple things Is modified by further in
vestigation. The explanation of how flies
walk on the ceiling, as given in some of
our old readers. was that each little fly
foot is q miniature air-pump-a theory
which Is now proved to be fallacious. 1t
was supposed that the bottom Of the foot
adhered to the glass by suction, all air
beneath it being pressed out SO that II
was held in place by the pressure of the
air without: but flies have been known TO
walk on the inner side Of a glass receiver
after all the air had been exhausted,
which shows that they do not need the
pressure of the air to uphold them. A
microscopic examination of a flys foot
clearly dsproves the sucker theory, for
the foot cushion is covered with hairs,
which prevent a close contact of the foot
with the glass.
"A later theory, propounded by HoolSe,
was that flies stick to the glass by means
of a Viscous fluid substance which exudes
from the hairs I'm their feet This theory
was thoroughly Investigated twelve years
or so ago by DR.. Rombout, who demon
strated that it was only partly sound, for
though these hairs do certainly exude an
oily fluid the fluid Is not sticky and does
not harden when dried.
1T is to DR., Rombouts experiments that
science owes what is now regarded as the
true theory of the walking of flies on
smooth substances. that they hang on by
the help of capillary adhesion-the MOLE
cular attraction between solid and liquid
bodies. BY a series Of nice calculations
such as Weighing hairs and measuring
their diameters, and immersing the cut
end of a hair in oil or water to make il
adhere when touched to glass-Dr. Rom
bout proved that capillary attraction
would uphold a fly we're it four-ninths
as heavy again as II IS at present. 1t is
true that the foothairs are very minute,
but as each fly is said to be furnished with
10000 to 1900 of them, we need not be
surprised at what they can do.
Reasoning from this theory, we might
conclude that flies find 1t difficult 10
mount d grass hBHtiy NhAlPthS"' DVCduSs
of the repulsion between the watery sur
face and the oily liquid exuding from the
feet and we might likewise expect them
to be impeded by a slight coating of dust,
because the spaces between the hairs
would be filed with dust. Careful obser-
vations seems to confirm these differences
When we see fly making his toilet. be
is not, as we might suppose cleaning his
body, but his feet, SO that they may the
more readily adhere. Every one has no.
ticed how quickly a fly takes flight, even
when he has been doing half an hour in
the same position. This new theory makes
It easier to understand how he can so
readily detach himself; for the air-pres-
sure theory and the gum theory both I'M
piled more or less effort In releasing his
feet from their Involuntary hold"