The Pascagoula democrat-star. (Pascagoula, Miss.) 1878-1920, 1897-10-29

HOW FLIES WALK ON THE
CEILING.

In old text books we were told TINT
ilics are enabled to walk ON the cell.
ing by means Of suckers" On their
feet, Il statement that might have
been dispr0ved by any one VIM took
the trouble to look ut u fiy's root
through q microscope. This, and
some later explanations OF what Is.
after all, still something of q mystery.
is discussed by G. II. Dierhold In
our Animal Friends (Septcmbcr.)
We quote his article below:
II Is "A curious fact how our under.
standing Of many common aud appa.
rcntly simple things Is modified by
further investigation. The cxplana.
tion Of how ilics walk on the ceiling.
as given In suine Of our old readers.
that eacl, little 0y-f00t Is a miniature
air-pump-a theory which Is now
proved to bc iallacious. IL was sur.
pissed that the bottom Of the foot ad.
lcred. to the glass by suction, all air
beneath II being pressed out, SO that
it was held in place by the pressure Of
the air without; but flies have been
known to walk on the inside Of a
glass receiver after all the air had
been exhausted, which Shows that
they do not need the pressure Ut the
air 10 uphold them. A microscopic
examination Of q hy's foot clearly dis.
proves the 'suckcr' theory, for the
foot Is covered with hairs, which pre-.
vent a close contact Of the foot with
the glass.
A later theory, propounded by
IlO0ke, was that flies stick To tho
glass by means OF Il yiscuous fluid
substance which cxudes from tho
hairs in their feet. This theory was
thoroughly investigated II years or
50 ago by DR.. RombOut, who demon.
strated that II 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 DR.. RombOut's experiments
that science owes what Is now regard.
ed AS the true theory of tic walking
of kfics on smooth substance, that
they hang on by the capillary adhc-
sinn-thc molecular attraction BE-.
tween solid and liquid bodies. by u
series of nice calcalaJi0ns--such as
weighing hairs aud measuring their
diameters, and immcrsing the cut end
Of a hair in oil water to make ii adj.
here when touched To glass-Dr. Rom.
bout proved that capillary attraction
would uphold Il ny werS it four-nintlls
Us heavy again as ~ IS at present. 1t
Is true that the foot-hairs arc very
minute, but Us eacl, fly is said to bc
furnished with ten to twelve Thousand
Of them, We need not be surprised at
What they can do.
Itdo''IIIhk IIpIu tuto t'o''st v
might conclude that flies find IL dim.
cult " mount Il glass lightly dampcn-
I'd. because Of the rcpulsiOn between
the watcry surface and the only liquid
exuding from the feet. and we might
likewise expect them To be impcdcd
by Il slight coating Of dust, because
the spaces between the hairs would
be filled with dust. Careful 0bsrrva.
seem to confirm these differences.
When We see a fly making his toilet,
he is NOT, us VIC might suppose, clean
ing his body. but his feet. SO that they
may the more readily adhere. Every
one has noticed how quickly a ny
takes fight, even when he has been
doing half an hour in the am posi-
ton. The new theory makes il easier
to understand how he can so readily
dctach himself; for the air-pressure
theory and the "gum' theory both
implied more or less effort In releasing
his feet from their involuntary hold.