SCORPIONIDA 405 



chelate; on the ventral surface the second abdominal segment bears a pair 

 of long comb-shaped appendages called the pectines, which probably aid in 

 the act of pairing, following which are 4 pairs of spiracles, each of which 

 opens into a lung sac; genital opening just in front of the pectines on 

 the first abdominal segment and protected by small paired plates, which 

 form the sternum; the young are born alive and are carried about for 

 a while by the mother : over 300 species, about 25 occurring in our south- 

 ern and western states, ranging as far north as Nebraska; they are 

 nocturnal animals and feed on insects and spiders which they often 

 kill Mith the sting. 



Key to the families of Scorpionida here described: 



fli Sternum broad, pentagonal ; usually no spine under the sting. 



&i At base of terminal segment of last pair of legs at least 1 spur on inner 



and 1 on outer side 1. Vejovidae 



62 But 1 spur present, on outer side 2. Scorpionidae 



Ca Sternum long, triangular; usually a spine under the sting. . .3. Centburidae 



Family 1. VEJOVIDAE. 



Three eyes on each side; terminal joint of legs with an inner and 

 outer spur at base; no spine under the sting: 8 genera and 18 species. 



1. Vejovis Koch. Median lamella of each comb divided into at 

 least 8 small pieces; lower margin of the movable finger of mandible 

 without sjDines: 6 American species. 



V. boreus (Girard). Hand strongly keeled; color yellowish or 

 greenish: Nebraska and westerly to Nevada and Idaho. 



V. mexicanus Koch. Hand less distinctly keeled; color brown, not 

 spotted; legs reddish; length 8 cm.; number of teeth of comb 15 to 22: 

 Texas. 



V. carolinus Koch. Color reddish-brown; legs yellow; length 34 

 mm.; number of teeth of comb 13 or 14: southern Atlantic states and into 

 Kansas and Texas; California. 



2. Hadrurtis Thorell. Large, hairy scoipions with a large, dark 

 spur near the tip of the lower margin of the movable finger of the man- 

 dible: 2 species. 



H. hirsutus (Wood). Color yellowish-red; length 7 cm.; number of 

 teeth of comb 25 to 40; legs compressed: California and Arizona. 



Family 2. SCOEPIONIDAE. 



Sternum pentagonal in shape; but 1 spur at the base of the last 

 tarsal joint, which is on the outer side; usually no spur under the sting: 

 15 genera and about 88 species. 



DiPLOCENTRUS Peters. With a hump under the sting: G species, all 

 American. 



