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Cheliferoidea

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Like the Cheiridioidea, this superfamily comprises monotarsate forms; it is usually included in the Monosphyronida by other authors. The femora of legs I and II are very different in morphology and articulation from the femora of the legs III and IV. The movable cheliceral finger is not dentate but has a subapical lobe. The plates of the serrula interior are mostly fused into a membranous velum. A lamina exterior and laminal seta are present on the fixed cheliceral finger. The subterminal tarsal setae may be simple or dentate. The carapace is usually widened posteriorly. The chelicerae are small, about one-third as long as the carapace. One or both chelal fingers have a well-developed venom apparatus. The abdominal tergites and sternites are usually divided. There are two eyes or none.
This is the larges superfamily of pseudoscorpions in terms of genera and species. Members are widely distributed but are most numerous in tropical and subtropical areas. They are found in litter and organic debris, under the bark of dead and living trees, and in nests of birds and mammals. Many are involved in phoretic relations with other animals. They range widely in size, but most are 2-3 mm in length.
Seven families are included: Atemnidae, Miratemnidae, Myrmochernetidae, Chernetidae, Pseudochiriididae, Withiidae, and Cheliferidae.

ATEMNIDAE

The venom apparatus is developed only in the fixed finger of the palpal chela.  The carapace is smooth with, at most, a shallow transverse furrow near the middle.  Usually there are two eyes.  Some tergites and sternites on the abdomen are divided.  The internal genitalia of the male are weakly sclerotized.  The spermatheca of the female is a single ovoid sac.  The cheliceral flagellum is composed of four setae.  The fingers of the palpal chela are not provided with accessory teeth.  The tarsus of leg IV has a prominent tactile seta near the proximal end.  The subterminal tarsal setae are curved and simple.

Members of this family are best represented in Africa and southern Asia; a few inhabit the warmer parts of Europe, America, and Australia.  Frequently they are found under bark and also under the elytra of large beetles.  Some have been shown to be social, cooperating in predation and nest spinning and engaging in multiple phoresy.  Most are moderate in size, 3-5 mm in body length.

About 15 genera have been described in this family, the most common being Paratemnus, in America; Oratemnus, in southeastern Asia; and Titanatemnus, in Africa.

MIRATEMNIDAE

The venom apparatus is developed only in the fixed finger of the palpal chela.  The carapace is granulate, and has two distinct transverse furrows.  There are two corneate eyes.  The abdominal tergites and sternites are usually not completely divided.  The hand of the chelicera has five setae.  The flagellum has four setae.  The fingers of the palpal chela lack accessory teeth.  The tarsus of leg IV has a prominent tactile seta near the middle.

This family is considered by some authors to be a subfamily of the Atemnidae.  Only 4 genera are placed here: Miratemnus, from South Africa; Diplotemnus, from Africa. Asia, southern Europe, and the southwestern United States; Tullgrenius, from southeastern Asia; and Brazilatemnus, from Brazil.  They seem to inhabit litter.

MYRMOCHERNETIDAE

This family is based on a single rare species (Myrmochernes africanus) from South Africa.  It was found in association with ants and is presumed to be modified as a myrmecophile.  Only a few specimens are known, and no recent study has been made on them; as a result, many significant characters are unknown. 

The body length is about 1.5 mm.  The carapace is nearly triangular, with two distinct transverse furrows and no eyes.  Most of the abdominal tergites are divided.  The body setae are short and clavate.  The basal and subbasal setae of the cheliceral hand are short and clavate and about equal in length to the interior and laminar setae.  The flagellum apparently comprises two dentate setae.  The palpus is short and stout; the chelal fingers lack accessory teeth.  The number and placement of the trichobothria and development of the venom apparatus are unknown.  Obviously, further work is required.

CHERNETIDAE

            The venom apparatus is well-developed only in the movable finger of the palpal chela; it is vestigial or absent in the fixed finger.  Both chelal fingers usually have accessory teeth located externally and internally to the marginal row.  There are two weak eyes or none.  The abdominal tergites and sternites are usually divided.  The internal genitalia of males are characteristic but difficult to describe.  The spermathecae of females are usually conspicuous, bilaterally developed tubes or sacs.  The cheliceral flagellum consists of three or four setae.  The tarsus of each leg has an elevated slit sensillum on the outer margin, proximal to the middle.  The subterminal tarsal setae are curved and simple.

            Some species have been shown to have complex courtship behavior, and there is frequently a conspicuous sexual dimorphism, usually involving the palpi, as in Mirochernes and Semeiochernes, which have bizarre processes on the chela of the male.

            This group is nearly cosmopolitan and is well represented in every region except the Arctic and Antarctic.  Members are found in nearly every habitat suitable for small, terrestrial predators.  Many have phoretic relations with other animals such as insects, birds, and mammals.  Some are cavernicolous, but are usually not noticeable modified morphologically.  Most are moderate size, 3-4 mm in length.

            This is the largest family of pseudoscorpions, and it includes many, varied forms.  Over 100 genera have been described.  The arrangement of these genera into subfamilies and tribes is in a state of flux.

PSEUDOCHIRIDIIDAE

            The venom apparatus is equally developed in both fingers of the palpal chela.  Accessory teeth are not present on the chelal fingers.  The carapace is generally triangular, but the posterior margin is produced backward at the middle; there are two distinct transverse furrows, and two weak eyes or none.  The abdominal tergites and sternites are divided, the individual sclerites slanted backward toward the middle to produce a chevron effect.  Most setae are broadly clavate and denticulate.  The cheliceral flagellum consists of tow or three setae.  The palpal chela has the usual number of 12 trichobothria.  The legs have the usual cheliferoid form.  The coax of leg IV is expanded posteriorly in both the male and the female so as to cover the genital opercula, more completely in the female than in the male.

            This small group is customarily considered a subfamily of the family Cheiridiidae.  Here it is judged to be a family rank and is placed close to the Chernetidae.  There are only two genera: Pseudochiridium, from Africa, Indonesia, and the United States (Florida); and Paracheiridium, from Madagascar.  They are all very small and are usually found in dry litter.

CHELIFERIDAE

            Members are in many ways the most advanced of the pseudoscorpions.  The venom apparatus is well developed in both fingers of the palpal chela.  Accessory teeth are not present in the chelal fingers.  The cheliceral flagellum consists of three setae.  Usually there are two distinct eyes.  The abdominal tergites and sternites are usually divided.  The internal genitalia of the male are complex and heavily sclerotized, usually possessing eversible lateral sacs called ramshorn organs.  The spermathecae of the females are in the form of one or two short, rounded sacs provided with conspicuous, cribrate sclerotic plates.  The secondary sexual modification of the males is often marked: projections from the posterolateral corners of the carapace and abdominal tergites, a short spur on the lateral side of the coxa of leg IV, and special modifications of the tarsus of leg I.  The subterminal tarsal setae are simple or dentate.  The pedal claws are simple or dentate.

            The marked sexual dimorphism is accompanied by complex courtship and mating behaviors, including extensions of the ramshorn organs of the male, dancing by the pair, and assistance by the male in taking up the spermatophore, using his modified first legs.

            The family is nearly cosmopolitan in distribution, but is best represented in the warmer regions of the world.  Cheliferidae are often found in litter; they also frequently live under the bark of trees, and are occasionally phoretic on tree-dwelling insects.  One species, Chelifer cancroides, is usually found in human habitations and outbuildings and has apparently been spread around the world by the movements of human beings.  Most are moderate in size, 3-4 mm in length.

            About 50 genera have been placed in this family, in 2 subfamilies: Cheliferinae and Dactylocheliferinae.

WITHIIDAE

            The venom apparatus is well developed in both fingers of the palpal chela. Accessory teeth are not present on the chelal fingers.  The cheliceral flagellum consists of four setae.  There are usually two distinct eyes.  The internal genitalia of the male are complex, but only moderately sclerotized, and lack ramshorn organs.  The spermatophores produced by the male are very specialized.  The spermathecae of the females are in the form of two short tubes with terminal cribrate areas.  The secondary sexual modification of the males is restricted to patches of small sensory (?) setae on certain abdominal sternites.  The subterminal tarsal setae and the tarsal claws are simple.

            There is a mating ritual, but with less sophisticated movements and more physical contact than in the Cheliferidae.  The sensory areas on the venter of the male may be used to position the pair properly over the spermatophore.

            The family is distributed around the world, but mainly in the warmer regions.  Withiids are found in litter and organic debris and in animal nests.  One species, Withius subruber, is found in stores of grain and in barns around the world, apparently spread by humans.  All are moderately small, about 2-3 mm in length.

            This group is viewed by some taxonomists as a subfamily of the Cheliferidae, but is here considered a separate family as suggested by P. Weygoldt.  There are about 30 genera assigned to this family; their relationships have not been worked out.