34 ARACHNOIDEA. 



CASE the tracheae) placed in the abdomen as in insects, and not only 

 are they in many respects analogous to the tracheae, but in some 

 spiders they are supplemented by one or two tracheae. Again, 

 one distinction between insects and spiders is, that the former 

 have never more than three pairs of legs, while the spiders have 

 four pairs ; but the first pair in the spiders are only modifications 

 of the palpi. Again, insects are divided into three parts, head,. 

 thorax, and abdomen. Spiders consist of only two or one part, 

 as in some mites; but all this is a mere modification of parts. 

 The head of the spider is merged in its thorax, so that no line 

 of separation can be drawn, but we know that the front belongs 

 to the head, and the back part to the thorax, by the organs 

 which they respectively bear. The mouth and its parts (along 

 with the anterior legs) in the one case, and the rest of the limbs 

 in the other case. It seems to us, therefore, that the arachnoids 

 are to be regarded as modified insects. 



Family SCORPIONID^ or PEDIPALPS (Scorpions and their allies). 



Anterior palpi elongated like legs, and provided with nippers like the claws- 

 of a crab. 



Sub-Family, PsEUDO-ScoRnoNES (False Scorpions). 



The cephalothorax is united to the abdomen, which is divided into segments. 

 No tail. 



Genus Chelifer (Z^/.). 

 Cephalothorax parted in two by a transverse furrow. 

 IJos. Chelifer museorum {Fab.).—\. Specimens (8) ; 2. Enlarged figure. • 



The chehfers are harmless minute insects, like scorpions in 



3,2 



appearance, but which, although possessing their nippers, are 

 destitute of the armed tail ; as in this species, the fore-legs (palpi) 

 are sometimes very long. They live in dark and moist places. 



