Savory - Arachnida 1977

28. THE ORDER PSEUDOSCORPIONES 221
28
The Order Pseudoscorpiones
[Pinces Geoffroy, 1762; Faux-scorpions Latreille, 1817; Cheliferes
Gervais, 1844; Chernetidae l\Ienge, 1855; Chernetes Si.mon, 1879;
Pseudoscopiones Pavesi, 1880; Chelonethi Thorell, 1885; Chelonethida
Cambridge, 1892; Pseudoscorpionides Beier, 1932; Pseudoscorpionida
Petrunkevitch, 1955]
( 1931) the ocular disc, median disc and posterior disc. The furrows
which separate these regions may be vestiges of the primitive segmentation,
but this is not certain. They do not appear to be related to the
insertion ofthe muscles within (Fig. 90).
The primitive number of eyes is four. Many species have two eyes
and many are blind, but these conditions appear to have been derived
by losses from the original complement. The eyes themselves are always
sessile, and are situated close to the fore-edge of the carapace-, except
when the cucullus is elongated, and the two on each side are always
close to one another. Structurally the eyes are of the pre-bacillar type,
as found in the indirect eyes of spiders. They possess a tapetum and shine
by reflected light. No false scorpion ever possesses median postbacillar
eyes like the direct eyes of scorpions and spiders, a fact which
is a definite characteristic of the order. In the two-eyed forms, the anterior
pair of eyes are retained, the posterior pair lost. The anterior eyes,
in general are directed forward in slightly divergent directions, the
Arachnida in which the prosoma is covered by an undivided carapace,
bearing not more than two pairs of lateral ~Jes. The opisthosoma consists of
12 distinguishable somites, the last reduced to a circumanal ring. The chelicerae
are of two segments and are chelate; th~J bear on the distal
:,egment a spinneret from which proceeds silk secreted by pro somatic glands.
The pedipalpi are very large, are of six segments and are chelate; venom
glands within open near the tip of the metatarsus or tarsus or both. The legs
are cif seven segments, the first two pairs distinguishable from the last two.
There are terminal claws with an arolium between them. There i:, no pedicel
and no telson. The manducatory apparatus is complex: the sternum is
usually absent. Two pairs of spiracles are found on the third and fourth
opisthosomatic somites.
The prosoma of Pseudoscorpiones is covered by a carapace, quadrate
or triangular in shape and almost certainly formed by a fusion of the
original sclerites. It bears the eyes, two or four in number, when present;
but some false scorpions are blind. Sometimes there are no transverse
markings or furrows, but often these are present and allow the carapace
to be divided into four regions. The first of these is the portion anterior
to the eyes and known as the cucullus. In some families the cucullus is
not distinctly separate, but in the Garypidae and Cheiridiidae it is
narrow and elongated. It is morphologically the same part as the usually
perpendicular clypeus of spiders, and is probably also homologous with
the distinct jointed cucullus of the Ricinulei. The posterior, thoracic,
portion of the prosoma consists of three parts, called by Chamberlin
FIG. 90. Pseudoscorpion, dorsal aspect. Species, Chelifer cancroides.