ARACHNIDA : SPIDERS. 



339 



FIG. 464. 



SUB-SECTION III. 



THE ORDER or ARACHNIDA OR SPIDERS, SCORPIONS, AND 



MITES. 



THE Arachnida are insects which have the body divided 

 into only two well-marked regions the head and hind 

 body, the head and thorax being 

 closely united in one piece, there- 

 by resembling the cephalo-thorax 

 of the Crustaceans. 



As regards their form, they may 

 be said to represent essentially 

 the same idea among Insects that 

 Crustaceans do among Articulates. 



Arachnids have simple eyes, 

 and four pairs of legs ; they 

 have no antennse, no wings, and 

 in general they do not change in 

 form after they are hatched from 

 the egg. In coming to maturity 

 they moult their skin six times. 

 The name Arachnida is from the Gr. arachne, a spider. 



By some writers the Arachnids are regarded as a Class, 

 separate from, and even higher than Insects; but their 

 form and structure seem to show that they are one grade 

 or type of the great group of Insecta, and lower than 

 Insects proper. They are less highly cephalized than typi- 

 cal hexapodous insects.* "We must look upon the Spider 



* Cephalization n. term introduced by Professor J. D. Dana refers to 

 head-domination. It refers not only to the head and its structure, but also 

 to " the extent to which the rest of the body directly contributes by it* 



An Arachnid Spider, Lyeoia 

 lenta, Hentz. 



