AMil.O-KdVl'TIAN SUDAN 



AiKiliMukal 

 L-liiiracliMS 



180 SCOiaUONb AND AI.MKn ANNTLATKI) Sril.DllS OV THE 



oxternallv bv oblique slits on th. under side of the ubdou.en (Fig. 21, ,■)• Kach of these 

 lun-sacs' contains a number of parallel lamelUe protruding fronr the wall ot the sac. 



Three parts are to be distinguished in the body of scorpions. The hrst ,s the 

 cephalothorax (Fig. 20, p), bearing the mouth-parts and limbs and covered above witlwa kmd 

 of shield- on this the eyes are arranged in three groups, one (composed of 2 to o eyes 

 on each side of the anterior margin and one (formed of two eyes on a small promn.ence) 

 in the middle. The second piece, broadly united with the cephalothorax, to form the 

 trunk of the animal, is the prteabdomen, called shortly " abdomen" (Fig. 20, r). It consists 

 of seven segments, the two first connected ventrally (Fig. 21) with the genital apparatus, 

 the third to the sixth each bearing a pair of the above-mentioned sl.t-hke " stigmata ^^ 

 of the breathing organs. The third piece is the tail-like postabdomen or " cauda 

 (Fic^ 20 0'), consisting of six segments with a poison-sting at the end ot the terminal 

 vesLular segment. This cauda is the most characteristic external feature ot scorpions 

 and distinguishes them at once from all allied forms of annulated spiders. 



The under side of the trunk shows, at the second ventral plate of the prceabdomen, a 

 pair of comb-like appendages (Fig. 21, c), likewise most characteristic of the scorpions. The 

 number of comb-teeth or comb-lamell* is valuable for distinguishing the species, as it 

 IS constant within cerfain limits. Somewhat in advance of these combs, the teeth of which 

 bear sense-organs, we find a pair of genital valves, touching each other in the median line 

 and in advance of them the "sternum," a triangular (Fig. 21, a) or pentagonal (Fig. 27) 

 plate situated just in the median line. 



The first pair of mouth-parts are the small mandibles, slightly prominent under the 

 front margin of the cephalothorax. The terminal joint is scissor-like and the two branches 

 of it called the movable and the immovable mandibular fingers, are frequently found armed 



with tooth-like prominences. 



The second, a very much better developed pair, are the large, limb-like maxillary palps, 



armed with powerful scissors at their ends. These make the animal somewhat resemble 



a crayfish, with the difference that the latter has the inner, but the scorpion the outer 



„ , " fincer " of the scissors movable. The maxillary palp is formed (1). by the basal joint (the 



,hema."illary ^oxa) with its margin directed to the median line adapted for chewing; (2), the trochanter, 



'^^"^ a rin.^-like short joint; (3), the femur and (4), the tibia, long, the joints acting somewhat 



like Ihe upper and fore-arm of man, and provided, as a rule, with more or less strong 



longitudinal ridges ; (5), the " hand " with its two " fingers." ^ 



The same divisions are to be distinguished when we investigate the four pairs of 

 walkin.' limbs of the thorax, which are nearly equal to one another in every respect, with 

 the single exception, that they become gradually a little longer, as one passes from the first 

 to the fourth pair. Coxa, trochanter, femur, tibia, all resemble those of the maxillary palps , 

 but the end of the foot is formed by a series of three tarsal joints, the terminal one provided 

 with a pair of more or less curved claws, the base of which is provided with a walkmg- 

 spine (Fig 24 tv). Free movable spines at the base of the terminal joint are called basal 

 spines (Fig. 24, 6) and a tarsal spine (Fig. 24, t) is found at the penultimate ]oint in the 

 scorpions of the genus Buthns. 



The scorpions are strictly terrestrial animals of nocturnal habits, hiding during the 

 d.n-time under stones, logs, the bark of trees, or in holes in the sand or soil. All are 

 predaceous, feeding on small insects which are seized with the scissors of the maxillary- 

 palps and held above the cephalothorax; then the cauda is bent upwards m a vertical 

 plane sufficiently far to enable the scorpion to observe his prey with his eyes and to 

 choose, therefore, the exact point where his sting is to be introduced into its body. 



