122 WHIP-SCORPIONS AND OTHERS 



two are present as free tergites, a primitive condition, and belong 

 to the segments bearing the third and fourth pairs of legs respec- 

 tively. Median eyes are lacking but a pair of lateral eyes may be 

 present which are reduced to small pale areas of cuticle in some 

 forms. The pedipalps are clawless, raptatory, rather robust and 

 often armed with characteristic spines and setae, while the legs of 

 the first pair are long and slender and used like antennae as tactile 

 sense organs. The abdomen is again composed of twelve segments, 

 the last three being small, annular and forming a pygidium which 

 bears a short caudal appendage made up of one to three, or oc- 

 casionally four, segments. In the males it is often fused into a 

 single rounded or elongate knob. 



Three genera only are found in the order: Schizomus and Trithy- 

 reus have a wide tropical and equatorial distribution, \Nhi\Q Stenoch- 

 rus contains a single species from Porto Rico. One or two species 

 have been described from specimens introduced into hot-houses 

 in temperate countries (Cloudsley-Thompson, 1949). The genera 

 Schizomus and Trithyreus can be distinguished by the fact that the 

 posterior free segment of the prosoma is divided by a longitudinal 

 suture in the latter. 



Biology 



Schizomida are absolutely nocturnal in their habits and spend 

 the day in damp, dark retreats under leaves, stones and logs, or 

 deep in the soil where the ground is moist. In Ceylon, Schizomus 

 crassicaudatus is found only under bricks, etc., on or close to open 

 ground more or less shaded by trees, while S. vittatus and Trithy- 

 reus paradenigensis occur among dead leaves especially where these 

 form a layer of considerable depth and are matted together by 

 fungal hyphae. Although they make no attempt to drink, they are 

 very susceptible to desiccation. In addition, they are strongly 

 photo-negative and are very sensitive to tactile and vibratory 

 stimuli. They can run surprisingly fast and, when touched in 

 front, escape by a sudden jump backwards. Approaching objects 

 appear often to be perceived — probably by means of vibrations — 

 before they are actually touched. The elongated front pair of legs, 

 highly sensitive tactile sense organs, are carried aloft and not used 

 in walking. Little is known of the biology of Schizomida. They pro- 



