100 FALSE-SCORPIONS 



chelicerae, pedipalps and four pairs of legs. The chelicerae are pre- 

 oral in position and are composed of two segments. Their fingers 

 bear a series of compHcated structures known as the serrulae and 

 laminae. The serrula exterior is keel-like, set with fine teeth and 

 attached for varying degrees of its length to the movable finger 

 while the serrula interior, attached to the base of the fixed finger, 

 is even more variable in form. A flagellum, formed of setae whose 

 number and shape are valuable taxonomic characters, is also at- 

 tached to the fixed finger. 



The mouth is situated between the basal segments of the six- 

 segmented pedipalps. These are enormously developed and re- 

 semble the claws of scorpions. They serve as prehensible organs to 

 capture and kill the prey and bear sensory hairs or setae. The im- 

 movable finger of the chelae has a row of cutting teeth along its 

 inner edge, the last of which is considerably enlarged. Through 

 this passes the duct of the elongated poison gland which itself is 

 embedded in the substance of the finger. In certain families both 

 fingers are equipped with poison glands. The coxae of the pedi- 

 palps are extended forward so as to form masticatory plates, or 

 they may bear distinct endites with which the prey is held in front 

 of the mouth during feeding. The four pairs of walking legs differ 

 from those of other Arachnida in that the tibia is undivided so that 

 there is no patella. At the same time in many species the femur is 

 divided into two more or less distinct segments. The number of 

 tarsal joints is of great systematic importance and is the chief 

 character upon which the three sub-orders of the Pseudoscorpiones 

 are differentiated. 



The opisthosoma or abdomen is broadly attached to the cephalo- 

 thorax and consists of 12 segments, the last of which is small and 

 forms a circumanal ring. The genital orifice is situated between 

 the second and third sternites, the second forming an operculum 

 while the first sternite is much reduced. 



The order Pseudoscorpiones contains over 1,500 species belong- 

 ing to three sub-orders all of which are represented in the British 

 fauna. False-scorpions are distributed all over the world with the 

 exception of the arctic and antarctic regions. At present, nineteen 

 families have been described, but the order is still by no means 

 well known and others may yet be discovered. Some genera have a 



