Spiders and Their Near Relatives 



AA. One or two spurs on each side at the base of the last tarsal 

 segment of the last pair of legs. . 

 B. From three to five lateral eyes on each side. 

 C. Sternum triangular (Fig. 22); usually a spine under the 



Sting. P. 25. BuTHIDyE 



CC. The lateral margins of the sternum nearly parallel 



(Fig. 34); sternum usually broader than long; no 



spine under the sting. P. 29. Ve|ovid/e 



BB. Only two lateral eyes on each side. P. 29. Chactid^e 



Family BUTHIDjE (Bu'thi-dae) 



The members of this family are most easily recognized by 

 the form of the sternum, which is triangular in outline (Fig. 22). 

 There are one or two spurs on each side at the base of the last 

 tarsal segment of the last pair of legs. There are from three to 

 five lateral eyes on each side. The hand of the chelae is rounded 

 and the fingers are long. The last segment of the tarsus of the 

 legs is not terminated by lateral lobes. There is usually a spine 

 under the sting. 



This is a large family, containing more than 150 known 

 species, representing 18 genera. Nearly one half of the species 

 of scorpions occurring in our fauna belong to it. These represent 

 four genera, which can be separated as follows: 



A. A distinct tarsal spur at the distal end of the first tarsal 



segment of the third and fourth legs (Subfamily 



Buthinae). P. 26. Uroplectes 



AA. No tarsal spur at the distal end of the first tarsal segment 



of the last pair of legs (Subfamily Centrurinae). 



B. The oblique rows of teeth on the edge of the fingers of the 



chelae have on each side a parallel row of minute teeth 



(Fig. 31). P. 27. Centrurus 



BB. The oblique rows of teeth on the edge of the finger 



of the chelae not accompanied by parallel rows of minute 



teeth. 



C. The ends of the oblique rows of teeth on the fingers of 



the chelae overlapping (Fig. 30). P. 27. Tityus 



CC. The ends of the oblique rows of teeth on the fingers of 



the chelae not overlapping but often connected in 



one direct line (Fig. 28). P. 26. Isometrus 



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