306 ; ARACHNIDA—SCORPIONIDEA CHAP. 
segments 3-6 and 8—and demonstrated that those of segment 
5 persisted, though without external aperture, as coxal glands, 
and those of segment 8 as the genital ducts. 
Classification. 
More than 350 species of scorpions have been described, 
but many of these are “doubtful,” and probably the number 
of known forms may be put at about 300. These are divided 
by Kraepelin* into six families and fifty-six genera. The best 
indications of the family of a scorpion are to be found in the 
shape of the sternum, the armature of the tarsi, and the number 
of the lateral eyes, while assistance is also to be derived from the 
shape of the stigmata and of the pectines, and from the absence 
or presence of a spine beneath the aculeus. 
The six families are: Buthidae, Scorpionidae, Chaerilidae, 
Chactidae, Vejovidae, and Bothriuridae. 
Fam. 1. Buthidae.—Sternwm small and generally triangular. 
Tibial spurs in the third and fourth legs. Generally a spur 
beneath the aculeus. Lateral eyes three to five in number. 
There are two sub-families: BUTHINAE and CENTRURINAE. 
The BuTHrINak, which possess a tibial spur, comprise fourteen 
genera, most of them Old World forms. The principal genera 
are Buthus, which contains about 25 species, and Archisometrus 
with 20 species. One genus only, Ananteris, is South American, 
and it includes only a single species. The genus Uvroplectes, with 
16 species, is almost entirely African, 
The CENTRURINAE, without tibial spur, are New World 
scorpions, though /sometrus europaeus (maculatus) is cosmopolitan. 
The principal genera are Zityus with 30 species, Centrurus with 
13, and Jsometrus with 6. 
Fam. 2. Scorpionidae.—Sternum broad and pentagonal, with 
sides approximately parallel. No tibial spur, but a single pedal 
spur. Generally three lateral eyes. 
Nearly a hundred species of Scorpionidae have been described, 
distributed among fifteen genera. The following sub-families are 
recognised: Diplocentrinae, Urodacinae, Scorpioninae, Hemi- 
scorpioninae, and Ischnurinae. 
1 Das Vicrreich, 8. Lief., 1899. 
