Savory - Arachnida 1977

216 III. PROLES ARACHNk~S
it nearly touches the metatarsus and a closed or almost closed space is
formed by the interlocking of their processes and cavities.
The female genitalia are shown in Fig. 88. Their disposition suggests
that the seventh bodily segment has been repressed and the first sternite
belongs to the eighth somite. Pollock ( 1967) records two observations of
mating. The male climbs upon the female's back, his fourth legs grasping
her opisthosoma. Insemination is effected by the third legs: there
seems to be no courtship nor, apparently, any spermatophore.
27. THE ORDER RICINt:LEI 217
Fm. 88. Ricinoides afzelii: female genitalia. (i) Fourth coxa; fourth trochanter;
(iii) vulva; (iv-vi; first, second and third sternites.
In addition to having no eyes, Ricinulei seem to be poorly supplied
with sense organs. In the only specimen dissected by Hansen and
Sorensen, an immature Ricinoides crassipalpe, no lyriform organs were
found on pcdipalpi, legs or opisthosoma. Nor do Ricinulei possess the
long thin spines often described as acoustic setae such as are found on
the legs of the Araneae. Their spatulate setae arc possibly organs of
touch, and a very curious seta is found standing in a small dcpressio_n
on the last tarsal joint of each of the three posterior It is short,
slightly broader at its upper than at it lower end and carries delicate
scattered branches all over its upper portion. The actual tip is, however,
bare.
The tracheal tubes by which Ricinulei breathe open on the prosoma,
at two apertures near its apparent posterior margin, above the third
coxae. The apertures are very small and are not visible in the intact
animal.
DISTRIBUTION
The Ricinulei are of limited distribution, and have so far been found
only in scattered regions in the tropical belt (Fig. 89). These arc on the
FIG. 89. Map showing distribution of Ricinulei.
west coast of Africa, in Central America, in Mexico and Texas and in
the Amazon basin. The two hemispheres contain different genera,
Cryptocellus from the New World and Ricinoides from the Old.
PALAEONTOLOGY
This order appears to have been more numerous in Carboniferous times
than it is today, for the number of fossil specimens that have been discovered
is almost comparable to the number captured as living animals.
Nine fossil species have been described, belonging to two genera.
The genus Polyochcra contains three species, P. alticeps, P. punctulata
and P. glabra. The first of these came from Coselcy in Worcestershire,
the other two from Mazon Creek, Illinois.
The genus Curculioides dates from 1837, the year before the description
of the first living Ricinuleid. It now contains six species, three from
America and three from Britain.
These two genera differ from the recent ones in the form of the second
coxae. In the living Ricinulei these coxae are broad and meet in the
middle line; in the fossil genera they are triangular and do not touch
each other. The genus Curculioides was at first placed in a separate
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