WHIP-SCORPIONS AND OTHERS 115 



Order palpigradi 



Classification and distribution 



The Palpigradi or Microthelyphonida are tiny creatures resem- 

 bling, as their alternative name suggests, miniature whip-scorpions. 

 The prosoma appears to consist of only two segments when seen 

 from above, the tergum of the segment bearing the fourth pair of 

 appendages forming part of the carapace; but ventrally there are 

 four sternites. The chelicerae are the only chelate appendages as 

 the pedipalps are leg-like and terminate in a pair of claws. Eyes 

 are absent and the mouth is a mere slit between the bases of the 

 chelicerae. The abdomen is distinctly segmented and is terminated 

 by a slender flagellum consisting of 15 segments. The external re- 

 productive organs of the adults are quite complicated and are 

 borne on the second and third abdominal segments. 



The order comprises but a single family, the Koeneniidae, con- 

 taining about twenty species in four genera. These minute Arach- 

 nida are widely distributed in southern Europe, Africa, America 

 from California to Chile, Siam and Australia. 



Biology 



Palpigradi show a marked avoidance of light and are usually 

 found under half-buried stones and in other damp and sheltered 

 places in company with spring-tails, myriapods, woodlice and 

 other retiring animals. A few species such as Koenenia spelaea, K. 

 draco and K. pyrenaica are troglodytes and have particularly elonga- 

 ted limbs with abundant sensory hairs. Micro-whip-scorpions ap- 

 pear to be dependent upon moist conditions and are extremely 

 susceptible to desiccation. During periods of drought they make 

 their way deep into the soil. 



Palpigradi can move with great agility, their pedipalps assisting 

 the other limbs in locomotion while their flagellum is held horizon- 

 tally behind the body. From the structure of their chelicerae it is 

 evident that these animals are carnivorous, but in view of their 

 minute size there can be few other animals small enough to be 

 suitable as prey. Wheeler (1900) found that the alimentary canal of 

 Koenenia mirahilis^ a species occurring in Texas, contained only 

 material resembling yolk particles and concluded that it was ad- 



