Savory - Arachnida 1977

210
Ill. PROLES ARACHNES
( 1) Notostigmata
(2) Holothyroidea
(3) Parasitiformes
( 4) Trombidiformes
( 5) Sarcoptiformes
(6) Tetrapodili
Vitzthum ( 1931 and 1940-43) generally recognized Oudemans'
(1923) classification, but Grandjean (1935) made a division of the
Acari based on the presence or absence of actinochitin in the setae.
This same character has been used by Evans, Sheals and l\1acfarlane as
recently as 1961 whc divided the Acari into two super-orders, the
Acari-Anactinochaeta and the Acari-Actinochaeta. This character is
not used by Krantz (1970) although his order Acariformes is equivalent
to the Acari-Actiniochaeta of the previous authors and Krantz's
Opilioacariformes and Parasitiformes together equate with Evans,
Sheals and l\1acfarlane's Acari-Anactinochaeta:
KRANTZ
Order Opilioacariformes
Sub-order Notostigmata
Order Parasitiformes
Sub-order Tetrastigmata
Sub-order J\1esostigmata
Sub-order Metastigmata
Order Acariformes
Sub-order Prostigmata
Sub-order Astigmata
Sub-order Cryptostigmata
GRAND JEAN
Super-order Acari-Anactinochaeta
Order Notostigmata
Order Tetrastigmata
Order Mesostigmata
Order J\Ietastigmata
Super-order Acari-Actinochaeta
Order Prostigmata
Order Astigmata
Order Cryptostigmata
In almost every animal taxon large or small, there is to be found one
group which in range and in numbers far surpasses the rest. The beetles
among the insects, the ungulates among the mammals are examples of
this, and among the Arachnida, the spiders and mites show the same kind
of supremacy.
The mites are the specialists among the Arachnida. In their often
parasitic mode of life, in their occasionally vegetarian diets, in their all
too frequent harbouring of protozoans and other organisms pathogenic
to man and other animals, and even in their attempts to return
to the water, they are an individualized group, separate, distinct from
the others of their class. They appear not to be as rich in species as
spiders, but this inequality is annually disappearing as mites attract
more and more attention; and like all specialists their successes are
limited by the fact of their specialization. Yet within these limits it
must be admitted that they reign supreme.
27
The Order Ricinulei
[Podogonata Cook, 1800; Meridiogastra Karsch, 1892; Ricinulei
Thorell, 1897; Rhinogastra Cook, 1899; Ricinuleida Petrunkevitch
1945]
Arachnida in which the prosoma is cooered by an unsegmented carapace, with
a cucullus joined to its fore-edge. There are no tryes. The opistho:,oma is ~f
nine somites, the true.fint somite is missing and the second forms a pedicel; the
last three are reduced to a narrow pygidium. The three median tergites are
dioided by two longitudinal furrows into three plates each. The sternum is
small, and is hidden by the coxae. The chelicerae are of two segments, and
are chelate. The pedipalpi are of six segments, chelate, and their coxae are
fused in the middle line, forming a camarostome. The legs are of seven
segments, with the trochanter and tarsi ~f the last three various(y sub-segmented.
All tarsi haoe two smooth claws. The metatarsus and tarsus of each
third leg of the male are modified to form accessory sexual organs.
The prosoma of Ricinulei is protected by a uniform carapace, roughly
square-shaped and unusually thick and hard. It is covered, as is the rest
of the body, by characteristic granulations, interspersed with setae.
Some of these setae are spatulate or club-shaped, with a longitudinal
groove and roughened surface: they are probably sense organs of a
special kind. The carapace has a central transverse groove of varying
length and often a number of other markings, probably indications of
some of the original somites. One of the chief characteristics of the order
is the cucullus, a wide, oval, slightly convex plate, articulating with the
anterior edge of the prosoma. This cucullus is readily movable and when
bent downwards it completely covers and protects the mouth and the
chelicerae. A similar cucullus is found in some other orders, where it
bears the median eyes: the cucullus is therefore regarded as being the
first somite of the body, one which is not as a rule separated from those
behind it and to which the direct eyes belong. The Ricinulei have no eyes.