268 Mr. R. I. Pocock on the Genera and 
notes upon the habits of the species of Solpuga he has ob- 
served. Many of these I take the liberty of quoting verbatim. 
Mentioning in a letter that his attention had been attracted 
to a specimen of a Natal species [probably S. hostzlis] by the 
sound it produced when burrowing, he replied as follows to 
a question of mine touching the stridulation of these 
animals :— Until the arrival of your letter I had never 
thought of attributing the sound to stridulation, but merely 
to the trituration of the creature’s powerful jaws against the 
hard ground in which they seem to prefer to dig their holes, 
the operation being performed with the jaws, and the sound 
ceasing when the spider stops digging. .... When walking 
into Hartley the other day I captured an example of a small 
species [probably S. sericea] which was running on the path 
in the hot sunshine, apparently searching for insects. ‘The 
same evening I secured a specimen of yet another species 
[probably S. Darlingi?], which came into my hut attracted 
by the light. I kept them alive for a day or two, but failed 
to detect any stridulating sounds whatever, though they both 
made a considerable noise by energetically biting at the sides 
of the boxes, one of them in a cardboard box nearly succeeding 
in gnawing its way through at one spot. The evidence, so 
far as it goes, only tends to increase my belief that the sounds 
made by the Natal species were caused by trituration, not 
stridulation. ... But, unfortunately, owing to their lightning- 
like activity it is impossible to keep these creatures in an open 
vessel, and as the above specimens were both new to me, I 
was afraid to experiment with them while free, for fear of 
losing them.” In a subsequent letter he adds:—“ I was 
interested to learn from you that the noise made by Solpuga 
is really stridulation. I noticed the grooving on the mandible 
in a very large nocturnal species which I came across on the 
Umfuli River [S. Darlingi’], but it never stridulated at all 
while I was examining it before putting it into the cyanide 
bottle. By the way, it is curious how much more rapidly 
these creatures succumb to the effects of this poison than 
either spiders or scorpions” *, And, lastly, writing in January 
* On the tenacity of life of scorpions Mrs. Monteiro (‘ Delagoa Bay: 
its Natives and Natural History,’ p. 192) makes the following remark :— 
“ A Jarge black scorpion was eight hours in my strongest poison-bottle 
before it succumbed to the deadly fumes. When I touched him with a 
stick after seven hours he elevated his wicked tail and opened his claws 
wide in a most savage manner.” The greater susceptibility of the Sol- 
puga to the fumes as compared with the scorpion is doubtless connected 
with the much richer development of its respiratory system, which 
consists of an elaborate system of tracheal tubes, branching throughout 
the body, that of the scorpion being composed of four pairs of small sacs. 
