A SPIDER 25 
segment being the one next to the last. The basal segment of 
the pedipalp is called the maxilla. The two maxille are flattened 
structures situated on the underside of the cephalothorax just 
back of the mandibles, their forward, medial margins, which cover 
the mouth, being used to lacerate and squeeze the food so that 
the animal juices can be sucked up. Spiders prey exclusively 
upon living animals; but they can take in only liquid food. 
The pedipalps of the female spider differ in shape from those of 
the male, and the two sexes may be distinguished in this way. 
In the female the pedipalp looks exactly like a small leg; in 
the male the terminal portion is expanded and very complex in 
structure, being used by the animal in the act of pairing. 
The third, fourth, fifth, and sixth pairs of appendages are the 
legs, each of which is composed of the following seven segments: 
the coxa, trochanter, femur, patella, tibia, metatarsus, and tarsus. 
The legs are used by the spider for a variety of purposes besides 
walking. They are important as tactile organs, their great length 
increasing their usefulness in this respect, and they undoubtedly 
compensate the animal in a certain degree for the lack of an- 
tenne. They are also of use in spinning and manipulating the 
web, the complex structure of the claws being associated with 
this function. 
The median plate between the maxille on the ventral side of 
the body is the labium; the one between the bases of the legs is 
the sternum. 
The abdomen. The dorsal surface is usually marked by several 
pairs of depressions which mark the points of attachment of mus- 
cles. At the hinder end, on the ventral surface, are three pairs 
of spinnerets. Study these carefully with the aid of a hand lens. 
At the end of each spinneret are numerous microscopic holes, 
from which is exuded the semifluid silk. This is made up of 
many soft strands, which harden as they unite to form the thread. 
A study of the embryology of the spider shows that the spin- 
nerets are homologous to abdominal legs. 
