SPIDERS AND 
SCORPIONS. 
(Aracft/ikfa.) 
Spiders and Scorpions have no antennae ami no distinct 
head and differ thu^i from Insects, ("entipettes and Millipedes. 
Their btxiy consists of only two sections, cephalothorax and 
abdomen, of which the former is to be regarded as formed 
by the fusion of head and thorax. They have six pairs of 
appendages, and the cephalothorax which bears them, is there- 
fore considered as consisting of six segments. The twelve 
segments of the abdomen have no app>endages. The first pair 
of appendages are the jaws or mandibles. The second pair are 
called ' palpi ' when they are ieg-like and used as tactile organs, ' 
as in Spiders; or 'chelae' when they are pincer-like, as in 
Scorpions. The third, fourth, fifth and sixth pairs are the legs. 
In a few cases the first pair of legs may be long and slender. 
They are then used not as tocomotory, but as tactile organs, as 
in the Whip-Scorpions, The respiratory organs are in some 
eases tubular tracheae, as amongst Insects, x\I ill i pedes and 
Centipedes, but in other cases they have become modified into 
'book-leaf tracheae ' or * lungs \ sac-like structures containing 
numerous lamellae arranged like the leaves of a book. 
We follow Pocock's classification of the group into nine 
orders : 
I. Scorpiones. Of the eighteen segments of the body of 
Scorpions the last five are long and narrow and form the tail. 
At the extremity of the tail is a hard and pear-shaped organ 
containing two poison glands and ending in a cur\'ed sting. 
The second pair of appendages are developed into powerful 
pincers with which the Scorpion grasps and holds its prey, 
whilst the flexible tail is rapidly thrown forwards and the 
pt^ison sting inserted. On the under side of the body, just 
behind the last pair of legs, there is a pair of curious comb-like 
organs, the ' pecten which is supposed to be sensory in func- 
