Savory - Arachnida 1977

236 III. PROLES ARACHNES
may be as long as the rest of the prosoma, and so powerful that it is
probably true to say that Solifugae have the most formidable pair of
jaws in the animal world (Fig. 101). The chelicerae are of two segments
and closely resemble the very much smaller chelicerae of the Pseudoscorpiones.
The first segment has a broad base or palm, continued into a
fixed finger. The second segment or movable finger articulates below
the of this prolongation, and works against it in a more or less
vertical plane. The broad parts of the first segment are oval in section, so
29. THE ORDER SOLIFUGAE 237
i
ii
iii
FIG. 101. Chelicera of Galeodes ararwides, female, from inside. After Roewer.
S, stridulating organ.
iv
that there is a trough or channel-like space above and below them. The
former admits light to the ocular tubercle while the latter contains the
rostrum. The interior of the base contains the powerful muscles which
close the jaws and in well-fed specimens much fatty tissue as well. There
are no internal poison glands or ducts: the teeth are solid chitin and the
bite of Solifugae is not poisonous, but fatal only because of its severity.
Both fingers are provided with teeth, the number and position of which
is not only different in different genera (Fig. 102) but also differs in the
two sexes of the same species. In the mature males the teeth are often
reduced to a mere ridge, and it is doubtful whether chelicerae so modified
can act efficiently for their true purpose. Iv!any males die shortly
after copulation, but those of some species have been known to feed
and survive for at least 30 days.
A copious provision of spines and setae is also found on the surfaces
of the chelicerae. Between the two there is an important relation. \Vhen
they are in use, biting a struggling captive, the basal segments move
relative to each other in a longitudinal direction, while the mandibles
which work vertically, open and shut in alternation. This quickly
FIG. 102. Chelicerae of male Solpugidae, showing diverse forms of llagella. After
Kraepelin. (i) Galeodcs; (ii) Rhagodcs; (iii) Solpuga; (iv) Hexisopus; (v) Daesia.
reduces the prey to a fluid state and the hardest parts are rejected unless
the particles are very small.
They also possess stridulating organs. A smooth quadrangular surface
is found on the inner side of each basal segment, where the two segments
almost touch each other, and associated with this patch are spines of
various stoutness. When the chelicerae are rubbed together a kind of
twittering sound is produced, similar to that produced by stridulating
spiders.
It is possible that these ridges serve two purposes, helping also in the
grinding of the food; and this may account for the peculiar rotary
masticating action of the chelicerae while the animal is feeding.
V