THE SHAPE OF THE STERNUM IN SCORPIONS 

 AS A SYSTEMATIC AND A PHYLO- 

 GENETIC CHARACTER 



ALEXANDER PKTRLXKE VITCH, Ph.D., 

 Assistant Professor of Zoology in the Sheffield Scientific School 



(From the Osborn Zoological Laboratory of Yale University) 



It is generally recognized that the shape of the sternum 

 furnishes one of the important characters for the distinc- 

 tion of families in recent scorpions. The small family 

 Bothriuridn? is the only one in which the sternum is com- 

 posed of two transverse plates. This family includes 

 seven genera, six of which occur in South America, while 

 the seventh (Cerrnphoniits) is an inhabitant of South 

 Australia and contains a single species. The families 

 Scorpionidae, Vejovidae, Cha?rilidaB and Chaetidae have a 

 distinctly "pentagonal" sternum with more or less par- 

 allel sides. The Chaerilidae belong exclusively to the old 

 world. The Chactidae are divided into three subfamilies, 

 the European Euscorpiinas and the neotropical Megacor- 

 minaa and Chactinae, which have Mexico for their northern 

 limit of distribution. The Vejovidae are unevenly dis- 

 tributed between the Old World and the New. One of the 

 eight genera composing this family is found on the shores 

 of the Mediterranean (Iurus, with a single species I. du- 

 foureius), another (Scorpiops) *with about eight species 

 in East India. Of the remaining six genera, two occur 

 in South America, while the other four belong to the 

 southern and western United States and to Mexico. The 

 family Seorpionidap, to which some of the largest scor- 

 pions belong, has representatives from various countries 

 and regions. It is usually divided into five subfamilies. 

 Of these the Urodaeinap are Australian ; the Scorpioninae 

 Asiatic and African; the Hemiscorpioninn- Asiatic; the 



