A Survey of the Scorpion Fauna of South Africa. 
99 
Opisthophthalmus perhaps serves the purpose of securing a better grip on 
the substratum, and it is interesting to note that such coarse granulation is 
completely absent in the species characterised by weak and elongated hands 
in the male, in which species apparently the characteristic burrowing habit 
of Opisthophthalmus is lacking : still, it should be added that certain species 
with smooth sternites are undoubtedly burrowers. Such coarse granulation 
on the sternites is not found in any other genus in South Africa, and the 
burrowing habit also is much less marked in other genera, though it is 
known to occur in Gheloctonus crassimanus. Amongst the Buthidae a 
somewhat analogous adaptation apparently is that met with in the first 
three caudal segments of Parahuthus hrevimanus and of Karashergia meihueni. 
These species, though only very indirectly related to each other, have each 
acquired a peculiar modification of the crests on the lower surfaces of the 
anterior caudal segments, which would seem to indicate an adaptation to 
the sandy habitat in which they live, both species occurring at Kakamas. In 
this case it is difficult to imagine that the result is a mere coincidence of 
purposeless variation. 
An interesting study in evolution is afforded by the stridulatory 
mechanisms found amongst our South African scorpions. Stridulation 
occurs in three different genera, Opisthophthalmus, Parabuthus, and Pan- 
dinus, but, curiously enough, by a different mechanism in each case. These 
were discovered and described by Mr. E. I. Pocock, and I have only a few 
remarks to add to his account. 
In the genus Parabuthus a stridulatory organ was first identified as such 
in P. flavidus, where the organ is strongly developed, the stridulatory area 
on the upper surface of the second caudal segment being narrowly channelled 
and crossed by stout ridges. According to information received from reliable 
observers, stridulation also occurs in species where that area is considerably 
less modified, the upper surface being broadly excavated and covered with 
granules, none of which are enlarged into transverse ridges : this is the case 
in P. capensis (fide A. Gibbons ) and in P. villosus {fide Prof. Pearson), and 
I believe it will prove to be general or universal in the genus. On the other 
hand, although in P. planicauda Poc. there is what appears to be a fully 
established stridulatory organ, the first two caudal segments being modified 
superiorly and the stridulatory area uniformly shagreened, yet stridulation is 
not known to occur in this species, living examples at Alicedale (F. Cruden) 
having been kept under observation for some time with negative results. In 
P. granulatus, on first inspection, there seems to be scarcely a trace of a 
stridulatory organ, the first and second caudal segments superiorly entirely 
Tesembling the succeeding segments, except that mesially there is a very fine 
granulation which is lacking in the fourth and fifth segments and almost so 
on the third segment : nevertheless, after trials with spirit-preserved material, 
