Marvels of the Universe 651 
intermediate stages before it attains its 
complete form. The almost microscopical 
Spider, when it hatches out, only diifers 
from its mature mother in point of size. 
There are, of course, internal differences 
to correspond with the external. The 
respiratory system of an insect consists of 
a series of tubes, with openings all along 
each side of the hind-body. These tubes 
are rendered non-collapsible by a continuous 
spiral wire of chitin, the horny material of 
which the hard parts of insects are formed, 
much in the same way as india-rubber gas- 
tubing is strengthened by a coil of metal 
wire. These tubes traverse every part of 
the insect, including the wings. In the 
Spiders we find some of these tubes also ; 
but the principal work of respiration is 
carried out in two (in the Bird Spiders, 
four) chambers called lung-sacs_ situated 
in the fore part of the hind-body, and 
having their openings in the under surface 
Photo bu ae [E. J, Spitta, LP RALS. 
Wells, SPURS INIaS, 
These are single, and in this way differ from those of 
insects, which are all composite. 
just behind the legs. An insect, after it has attained adult form, does not cast its skin; but a 
Spider does. 
The Spider whose huge snare frequently confronts us in the garden is familiarly known as the 
Garden Spider, sometimes as the Cross Spider, from the fact that it bears upon its back certain lines 
and spots that at a little distance have the 
appearance of a cross. The adult Garden 
Spider has a very hump-backed look, owing 
to the great development of the hind-body. 
Having constructed its snare on geometric 
lines—many “ spokes ”’ radiating from the 
centre to the boundary lines, and strength- 
ened by a spiral of enormous length that 
runs round and round, knitting them all 
together—the Spider sits in the centre 
waiting for any small winged creature that 
may blunder into it. Her senses are so 
acute that she can tell the moment this 
happens, and in what part of the snare she 
may look for her victim. 
The head of the Spider ends in two 
very prominent cone-shaped bodies, which 
perform the function of pincers and are 
called the “ falces,” the cone part of each 
falx being called the base, whilst the 
hooked extremity is called the fang. Each 
fang is hard, sharp and curved, being mov- 
able at its attachment to the base, which 
Photo by\ [E. J. Spitta, FLR.M.S. 
THE SPIDER’S NIPPERS. 
The ‘‘falces,’’ or nippers, are here shown with the fangs 
closed down, where they lie between the rows of teeth. Notice 
the curious jointing. 
