Democratic Northwest. [volume] (Napoleon, Ohio) 1869-1894, 1890-07-24
HOW SPIDERS SPIN.
Wonderful Processes Disclosed by
the Microscope.

the Microscope.
Till lately little was known of the spin
ming organs of spiders. These occupy q
small round area on the under surface Of
the abdomen, and when at rest form a
blunt, conical protuberance. When ex-
amined by the microscope this prom
inence is found to contain four conical
spinnerets, their bases forming quadri-
lateral, and their apices meeting in the
centre. A tongue-like process fills the
space between the anterior pair. Each
of the spinnerets is two -jointed and fur
nished at its extremity with many hair
like tubes containing the ducts of spin
ming glands. They are possessed of won
derful mobility, and can be widely
separated or energetically rubbed against
each other with rotary motion at the
will of the animal. When separated they
disclose third and smaller pair of spin
nerets, consisting of one joint only, and
having their apices directed backwards
and inwards so as to lie Immediately
below the apices of the posterior pair.
These also have a large number of
glandular orifces, and are called inter-
mediate spinnerets. The three pairs
have about six hundred spinning tubes.
There are five different kinds of glands
and different numbers of each. There
are two pairs of Ampullaceal, three pairs
Of Aggregate, three pairs of Tubuliform,
two hundred Piriform, and about four
hundred Aciniform glands. To ascertain
the functions of the various glands, a
spider must be captured and secured so
that the spinnerets may be seen under
the microscope. The fourth pair of legs
must be kept back with pins, else they
will be used to break the threads. Each
of the anterior pair generally gives out
one large thread, and these two remain
distinct lines. If the spider cannot
break the lines, it will throw out other
two from the inner spinnerets, but all
four still remain distinct and do not ad-
here. If the spider wishes to strengthen
the line still more it will rub these spin
ming organs together and send out many
more lines, but the first four still remain
visible and are the largest.
Spiders having been watched while
capturing flies, it was observed that the
fly is held and rotated with the fore legs,
jaws and palps while the fourth pair of
legs draw out the silk by which the fly
is bound.
The foundation of straight lines of the
web are composed of two lines which
may be strengthened by other two. The
spiral lines are quite different. These
look like globular buds regularly ar
ranged on string. The globules are
composed of viscid matter added as the
line leaves the body. The ground line is
first two distinct lines, but is soon, after
leaving the body, joined into one by a
viscid substance and pressed by the fourth
pair of legs.
Spinning the egg cocoons appears to
be the function of the Tubuliform
glands, the color and size of this thread
being different from the ground-line.
The diameters of the spiders threads are
found to range from .OO6 to .0022 nm.
A foundation line is secured to another
object, and cross-lines to each other by
patches of silk. This is obtained by
rubbing the spinnerets against each other.
A good means of studying the work of
a spider is to imprison one in clear
glass bottle, when the origin of the diff
ferent lines, and the manner in which
the animal works may be carefully
watched. Journal of Microscopic
Science.