426 ARACHNIDA—SOLIFUGAE CHAP. 
shown by Bernard! to be due to the enormous development of the 
chelicerae, by the muscles of which they are entirely occupied. 
The floor of the cephalothorax is for the most part formed 
by the coxae of the appendages, and the sternum is hardly re- 
cognisable in many species. In Solpuga, however (see p. 429), it 
exists in the form of a long narrow plate of three segments, end- 
ing anteriorly in a lancet-shaped labium. 
A pair of large simple eyes are borne on a prominence in the 
middle of the anterior portion of the cephalothorax, and there are 
often one or two pairs of vestigial lateral eyes. 
The first pair of tracheal stigmata are to be found behind the 
coxae of the second legs. 
The mouth-parts take the form of a characteristic beak, con- 
sisting of a labrum and a labium entirely fused along their sides. 
The mouth is at the extremity of the beak, and is furnished with 
a straining apparatus of complicated hairs. 
The abdomen possesses ten free segments, marked off by dorsal 
and ventral plates, with a wide membranous lateral interval. 
The ventral plates are paired, the first pair forming the genital 
opercula, while behind the second and third are two pairs of stig- 
mata. Some species have a single median stigma on the fourth 
segment, but this is in some cases permanently closed, and in the 
genus Rhagodes entirely absent, so that it would seem to be a 
disappearing structure. 
The appendages are the six pairs common to all Arachnids— 
chelicerae, pedipalpi, and four pairs of legs. The chelicerae, 
which are enormously developed, are two-jointed and chelate, the 
distal joint being articulated beneath the produced basal joint. 
In the male there is nearly always present, on the basal joint, a 
remarkable structure of modified hairs called the “ flagellum,” and 
believed to be sensory. It differs in the different genera, and is 
only absent in the Eremobatinae (see p. 429). The pedipalpi are 
strong, six-jointed, leg-like appendages, without terminal claw. 
They end in a knob-like joint, sometimes movable, sometimes 
fixed, which contains a very remarkable eversible sense-organ, 
which is probably olfactory. It is concealed by a lid-lke struc- 
ture, and when protruded is seen to be furnished, on its under 
surface, with a pile of velvet-like sensory hairs. 
The legs differ in the number of their joints, as the third and 
1 Trans. Linn. Soc. (2), vi., 1896, p. 310. 
