CHAPTER 



I: SPIDERS AND THEIR NEAR 

 RELATIVES 



Class Arachnida 



I.— THE ZOOLOGICAL POSITION OF THE ARACHNIDA 



Spiders, scorpions, harvestmen, mites, and certain other 

 less familiar forms constitute a group of animals which is known 

 to zoologists as the Class Arachnida (A-rach'ni-da). 



This is one of several classes of animals that agree in having 

 the body composed of a series of more or less similar rings or 

 segments, and in having some of these 

 segments furnished with jointed legs 

 (Fig. i). All the animals possessing 

 these characteristics are classed together 

 as the Arthropoda (Ar-throp'o-da), 

 which is one of the chief divisions or 

 phyla of the animal kingdom. 



A similar segmented form of body 

 is found among worms; but these are 

 distinguished from the arthropods by 

 the absence of legs. It should be re- 

 membered that many animals com- 

 monly called worms, as the tomato- 

 worm, apple-worm, etc., are not true 

 worms, but are the larvae of insects, and 

 have legs (Fig. 2); the angle-worm is 

 the most familiar example of a true 

 worm. 



The Phylum Arthropoda is the 

 largest of the phyla of the animal king- 

 dom, including many more species than all the other phyla taken 

 together. The more familiar of the classes included in it are the 

 six mentioned below. Besides these there are other classes, 



Fi K . 1. A SCORPION. ONE 

 OF THE ARTHROPODA 



