By Rev. SAMUEL BARBER.
The instinct of spiders in at once attacking a vital part of their
antagonist--as in the case of a theridion butchering a cockroach by
first binding its legs and then biting the neck--is most remarkable;
but they do not always have it their own way. A certain species of
mason wasp selects a certain spider as food for its larvæ, and,
entombing fifteen or sixteen in a tunnel of mud, fastens them down in
a paralyzed state as food for the prospective grubs.
Perhaps the most entertaining points in connection with spiders are
their concentration of energy, their amazing rapidity of action, and
their inscrutable methods of transition and flotation.
During the past autumn large numbers of these creatures appeared at
intervals. Thus I observed a vast network of lines that seemed to have
descended over the town of Whitstable, in Kent, and which were not
visible the day before or the day after. Many were fifteen to twenty
feet long; they stretched from house to lamppost, from tree to tree,
from bush to bush; and within six or seven feet of the ground I
counted, in a garden, twenty-four or more parallel strands. The
rapidity with which spiders work may be gathered from the fact that,
while moving about in my room, I found their lines strung from the
very books I had, a moment before, been using.
Insect life, as might have been expected after so mild a winter and so
dry a spring and summer, is (1896) intensely exuberant. The balance is
preserved by a corresponding number of Arachnida. On May 25 and 26 the
east wall of the vicarage of Burgh-by-sands was coated with a tissue
of web so delicate that it required a very close scrutiny to detect
it. I could find none of the spinners. Every square inch of the
building appeared coated with filmy lines, crossing in places, but
mostly horizontal, from north to south.
Walking by the edge of a wheatfield in Suffolk on May 14, I observed
all over the path, which was cracked with the drought, dark objects
flitting to and fro. They were spiders--mostly of the hunting order.
Tens of thousands must have occupied a moderate space of the field,
and the cracks in the parched soil afforded them a handy retreat.
In reference to the visitation of spiders at Whitstable during the
autumn and winter of 1895-6, it is right to note that the people of
that place regard them as a sign of an east wind. In this connection
we can note the fact of the phenomenal clouds of flies occurring at
times on the east coast of England; and it would be interesting if
observers could ascertain whether spiders ever cross the Channel and
accompany such visitations of insects.
The production of the flotation line, and its method of attachment,
are the two points to which I ask the attention of observers.
Is it not evident that air (and probably at a high temperature) must
be inclosed within the meshes of the substance forming the line when
it passes from the spinnerets into the atmosphere? The creature with
this substance within its body drops to the ground at once by force of
gravitation; yet, when emitted, the very same substance lifts it into
the air. It has been usual to explain the ascent by the kite
principle, i.e., the mechanical force of the contiguous atmosphere.
But air movements, especially on a small scale, are so capricious and
uncontrollable that, without a directive force, the phenomena seem
quite inexplicable.
Moreover, all my own observations lead me to accept the theory of a
direct propelling force, and I can hardly accept the conclusions on
this point of Mr. Blackwall, though he is an authority on the subject.
The intense rapidity with which the initial movements are made cannot
be reconciled with any theory of simple atmospheric convection; and
illustrations such as the following go to prove that spiders possess
the faculty of weighting or condensing the ends of their threads, and
throwing them, within limited distances, to a point fixed upon.
I was writing, and had two sheets of quarto before me. Perceiving a
small spider on the paper I rose and went to the window to observe it.
To test its power of passing through the air, I held another sheet
about a foot from that on which the creature was running. It ascended
to the edge, and vanished; but in a moment I saw it landing upon the
other sheet through midair in a horizontal direction, and picking up
the thread as it advanced.
In this case there was no air movement to facilitate, nor any time to
throw a line upward, which, indeed, would not have solved the
difficulty. Propulsion appears the only explanation.
The next illustration is more marvelous, and seems to indicate that
some species, at any rate, have the power of movement through the air
in any direction at will.
Some years ago, at a dinner party in Kent, four candles being lighted
on the table, I noticed a thread strung from the tip of one of the
lighted candles close to the flame, and attached to another candle
about a yard off; and all the four lights were connected in this way,
and that by a web drawn quite tight. No little surprise was caused
among the guests on finding that the diamond form of the web was
complete.
No satisfactory explanation of this has been offered, and I can only
suggest that the spinner was suspended at first by a vertical line
from above, and thus swayed itself to and fro, from tip to tip of the
candles. It was certain that the spider could not have ascended from
the table; and it was equally certain that aerial flotation of the
line from a fixed point was impossible, as it involved floating in
four opposite directions. I have seen a creature of this or a nearly
allied species moving laterally through the air of a room in this
way.--Knowledge.
* * * * *