214 R. I- POCOCK [march 



pages I have treated them entirely apart. The best known members 

 of the Uropygi are sometimes called whip-scorpions, in allusion to 

 their superficial resemblance to the true scorpions, and to the thread- 

 like form of the long many-jointed tail-piece. They were formerly 

 comprehensively spoken of in works on zoology as Thelyphonus. Simi- 

 larly the Uropygi, which, owing to the shortness and greater width of 

 the body and to the absence of a " tail," are more like spiders than 

 scorpions, are better known collectively as "Phrynus." 1 



The Solifugae (or Solpugas) constitute a fourth " group " of Arach- 

 nida, very distinct indeed from the scorpions, Pedipalpi, and spiders, 

 though often by the uninitiated confounded with the latter on account 

 of their similarity in external form. The most familiar names con- 

 nected with this order are Galeodes and Sotyntr/a. 



In many respects these Arachnida and the scorpions are well suited 

 for the study of zoo-geographical problems. In the first place, as 

 compared with other terrestrial invertebrates, they are for the most 

 part of considerable size, and are on that account not likely to have 

 been overlooked by collectors in any of .the land-areas, like New 

 Zealand, where they appear to be absent. In the second place, the 

 mutual relationships of the genera 2 are tolerably well understood. In 

 the third place they are practically dependent for their dispersal upon 

 continuity of land, since they cannot fly, and there is no reason to 

 suppose that they are able to swim or even to float ; nor is it likely 

 that they can withstand immersion for any length of time in either fresh 

 or salt water, and except in the case of one or two species of scorpions, 

 there is no evidence, nor indeed any reason to think, that their dis- 

 tribution is due to human agency. In the fourth place, since they are 

 exclusively carnivorous, and will eat anything in the way of animal 

 life from small vertebrates to insects, centipedes, and worms, none of 

 the species are limited by the nature of their diet to any one particular 

 locality, their food being universally distributed. 



Lastly, although they reach the maximum of their development 

 both as regards size of individuals and numbers of species and genera 

 in the tropical and warmer temperate parts of the world, it would be 

 erroneous to suppose that they are only capable of supporting life in 

 countries where the temperature is warm and fairly uniform throughout 

 the year. Scorpions, for example, are found at high altitudes in the 

 Alps (7000 ft.), and as far to the south in Patagonia as the 50th 

 parallel of latitude, where the mean temperature of winter is a little 

 above freezing-point. Species of Galeodes (Solifugae) occur in the 

 steppes of South Eussia and Western Asia where the scorching heat 

 of summer is succeeded by a winter of corresponding rigour. Even 

 the whip-scorpions (Thelyphonidae) extend in Eastern Asia up to about 



1 In systematic zoology this name has dropped out of use as a synonym of the older 

 name Tarantula. 



2 Except possibly in the case of some genera of Solifugae. 



