Evening star. [volume] (Washington, D.C.) 1854-1972, 1905-07-18
HOW INSECTS WALK
GIFTS WITH WHICH NATURE HAS
ENDOWED TEEN.
Each Fitted to Dwell in His Own En-
vironment-Habits Of the
Mole Cricket.
from the English Illustrated Magazine.

From the English Illustrated Magazine.
Everybody, doubtless, is familiar with tho
common bluebottle fly and has observed its
six black legs and probably concluded that
these terminate in six feet.
Now, If a detached leg of the blowf1y Is
seen by a person possessing normal vision
he would have little difficulty in arriving at
the conclusion that he was looking at the
leg of a fly and If it should be viewed
through a reading glass 1t would probably
be even more easily distinguished as such.
But now let us place under a microscope
small portion Of this insects leg, which
roughly measures three-eighths of an inch
In length; say we magnify the twenty-fifth
part of an inch of the foot end. and see
! what is then revealed 1 wonder how many
of my readers would recognize these OBJ
jects as tiny portions from the foot end OF
the legs of the familiar blowfly-yet such is
the fact. 1t will be seen that various de-
tails have come into view which previously
were quite unknown to u.s. What are these
curious structures and what is their func-
ton? are questions that naturally follow.
Claw-Footed Fly.
In the first place, 1t is obvious that each
foot of the blowfly is provided with a pair
of stout claws. These are Of service to the
insect when walking over rough surfaces or
penetrating tiny crevices quite invisible to
human sight. For example, when 1t climbs
a perpendicular wall or walks upside down
upon ceiling the apparently smooth sur
face has sufficient roughness for these tiny
claws to get grip on it. However 1T Occa-
sionally occurs that the blowhy has other
situations to meet, where 1t cannot use
these hooked claws to any advantage. For
instance, in its casual roaming 1t may
alight upon the smooth surface of the
butchers scales and dishes or occasionally
1t appears to confuse the transparent VIM
dow panes of the shop with the surround
ing atmosphere. In the latter case we see
1t butting at the glass, with alternate ram
bles up and down the pane, as if 1t were in
great state of perplexity over the mex
plicable discovery that portion of the at
mosphere had suddenly become tough and
hard to penetrate.
The point we need to particularly OBJ
serve. however, is that the fly walks up the
perpendicular smooth glass with perfect
ease, although there is here no rough sur
face on which Its claws can find a hold.
This brings US to the next point in the an
atomy of the foot of this insect, namely, the
two pads seen between the claws. These
pads are brought into play on such smooth
surfaces as that of glass and similar mate
rails, the claws being then thrown back,
one to each side, beneath the foot and out
of the way, just when the claws are in
use the pads are lifted up between them,
also to be out of the way
Gum on the Feet.
These pads or flaps act by adhesion and
for long time were thought to hold, like
suckers, by forming a vacuum; but when
some flies were put into a vessel from
which the air was withdrawn, and the flies
still adhered 1t was conclusively shown that
mistake had been made, and some other
explanation was necessary Since then 1t
has been observed that the under side of
these foot flaps are studded with tiny hairs
which exude sticky fluid and 1t has there
fore been surmised that this secretion both
expels the air from beneath the pads and
at the same time gums the pads to the
smooth surface In this way 1t is explained
that when we find dead fly still adhering
to window pane frame 1t secreted this
sticky fluid while its strength was falling
and later became too feeble to remove its
feet again. OF course, a hold of this kind
would stand considerable pull, and so 1t
bears the weight of the fly when upside
down. When the active fly would lift It's
foot 1t loosens the pad by rolling It off the
surface from opposite sides, just as we
might readily open an envelope by pulling
up the flap by the point before it has prop
erly stuck, although it would be extremely
difficult to open by pulling directly from
above.
Although various views in explanation of
the exact use of these adhesive organs
which are familiar on many other flies be-
sides the blowfiy, and also on bees butter
lies and other insects have been put for
ward from time to time yet that given here
Is perhaps the most probable and the one
most largely accepted among biologists.
The remaining structures worthy of no.
t1ce in the blowfiy's foot are the stout bris-
ties which clothe its joints and also the
longer and more delicate ones, termed touch
bristles. seen nearest the pads, which are
probably associated with the sense Of
touch, and serve to direct the insect to suit
able footholds. The coarser bristles may
serve a variety of purposes in the econ
oIny OF the insect acting as brushes combs
&c, as may be observed by watching a fly
arranging its toilet
There Is another variety of the pad and
claw arrangement. This example is that
or an 1ncheumon fy-a parasitic fly whose
business 1t is to seek out plump and healthy
caterpillars and carefully deposit its eggs in
their bodies its offspring eventually feeding
on the substance of their caterpillar host
Now, If the reader will think for one mo-
ment of this insects occupation and then
glance at its strong comblike claws and
consider the plump and soft bodies of the
caterpillars it has to deal with, no large
effort of the imagination will be REQUIRED to
understand how the caterpilars are per-
suaded into a gentle submission to the egg
depositing business when gripped with six
feet like this.