600 
ARTICULATA. 
Class III. ARA€HJ\II>A. 
GARDEN-SPIDERS. 
This class includes spiders, scorpions, mites, &c. ; tliey are distinguished by aerial respiration, 
and the possession of four pair 
of legs, attached to the anterior 
part of the body. They have 
no antennae ; the jaws termi- 
nate with a claw-like joint, 
which conveys poison into the 
wounds inflicted by them, this, 
in the larger species only, being- 
injurious to man, though usu- 
ally fatal to the insects on 
which they prey. Tlie legs are 
generally formed of the same 
joints as those of insects. All 
the species are unisexual; all 
lay eggs, with the exception of 
the scorpions and a few mites, 
in which the ova are retained 
in the oviduct till they are 
hatched, and are thus pro- 
duced alive. They are divided 
into five orders, the Dimerosomata, Polymer osomata, Adelarthrosomata, Acarina or Mo7iomeroso- 
mata, and Podosomata. 
ORDER 1. DIMEROSOMATA. 
This order derives its name from the Greek ditnera, divided into two parts, and somaia, bodies, 
and includes generally those creatures 
which we call Spiders. In these the 
body consists of two distinct portions, 
of which the anterior, or cephalothorax, 
is usually of an oval form, and covered 
with a plate of a somewhat horny con- 
sistence, while the posterior, or abdo- 
men, generally forms a soft, roundish 
mass, without any traces of segmenta- 
tion, and which is attached to the base 
of the cephalothorax by a narrow pe- 
duncle. On its anterior portion the 
cephalothorax bears six or eight sim- 
ple eyes ; below and in front of these 
are seen the large mandibles, which 
serve these animals for the destruction 
of their prey ; beneath is the opening 
of the mouth, furnished with a pair 
of masticating jaws, or maxillae. These 
organs occupy the front of the cephalo- 
thorax; the lower surface of this bears 
four pairs of jointed legs, furnished at 
their extremities with claws, which are often of a very singular, comb-like structure. 
THE GARDEN-SPIDEK AXD TRAP-DOOR SPIDER. 
