94 
ANIMAL ACTIVITIES. 
Under the abdomen near the cephalothorax find two 
openings to the air-sacs or rudimentary lungs. 
Summary of Drawings, (a) A spider seen from 
above X 3- 
(i b ) A front view of the mandibles X 5 - 
(^) A view of the top of the head showing the ocelli. 
(d) A hind foot much enlarged. 
The Spider’s Activities. We have already con¬ 
sidered the activities of the grasshopper, classifying 
these under six heads. We 
have spoken of these six 
kinds of activities as the .six 
functions of living things. 
In the spider these activities 
are carried on by the aid of 
finely adjusted machinery 
which we can only describe 
somewhat roughly here. 
F IG . 85.—A Spider’s Leg. which we can only describe 
Taking Food. The devices by which spiders of 
different kinds procure their food are well worthy of 
study. Nearly all spiders are aided in this work by 
silken threads spun from their own bodies. In the 
lower part of the spider’s abdomen there is a bag in 
which is secreted a glue-like substance which issues 
from the spider’s body at will, and hardens on exposure 
to the air. The wart-like projections on the lower side 
of the abdomen near its posterior end are pierced with 
many hundreds of minute holes, through each of which 
proceeds a microscopic thread of the glue-like fluid we 
have mentioned. The wart-like projections are called 
spinnerets. The hundreds of tiny threads from the 
spinnerets are grasped by the spider’s claws and twisted 
into several strands, which, woven together, make the 
fibre of which webs are built. A spider’s thread, then, 
is a rope of several strands, and each strand is com¬ 
posed of many hundred lines, yet it is so light that it 
floats in the air, so strong that it easily holds up many 
times the spider’s weight, so elastic that it does not 
