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Families
Neobisioidea

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Members are diplotarsate; that is, the tarsi of all walking legs consist of two segments. For this reason Neobisioidea are assigned to the suborder Diplosphyronida by many taxonomists. Also, there are distinct teeth along the inner margin of both fingers of the chelicera. The plates of the serrula interior of the chelicera are not basally fused. No laminal seta is present on the chelicera. Usually the subterminal (st) setae on each pedal tarsus are forked, or at least distinctly dentate. The carapace is usually rectangular as viewed from above. The chelicerae are moderately large, about half as long as the carapace. One or both of the palpal chelal fingers are provided with a functional venom apparatus. The abdominal tergites and sternites are not divided. The vestitural setae are usually long and acuminate. Often there are four eyes, but there may be only two or none.
This superfamily is widespread in all the faunal areas of the world. Members live mainly in soil and litter; many are found in caves, especially in Europe and America, where they may be strikingly modified for cave life. They range widely in size, from soil dwellers with a body length less than 1 mm to troglobites over 6 mm long.
Seven families are included: Neobisiidae, Syariniidae, Ideoroncidae, Hyidae, Bochicidae, Vachoniidae, and Gymnobisiidae.

NEOBISIIDAE

A venom apparatus occurs only in the fixed finger of the palpal chela. The pleural membranes of the abdomen are distinctly granulate. The line of articulation between the basifemur and the telofemur of leg IV is perpendicular to the long axis of the femur. The carapace is rectangular or square when viewed from above, and often bears an epistome on the anterior margin. Four eyes are usually present, but the number may be reduced to two or none, especially in the cavernicolous forms. A spinneret or galea is usually present, although often reduced in size. The palpal chela usually has 12 trichobothria, but occasionally the number is reduced, as in Microbisium, which has seven trichobothria on the fixed finger and three on the movable finger.
This family is found mainly in the Northern Hemisphere, where it is common and widely distributed; only a few representatives are known from Africa and southern Asia. They live in soil and litter, and many have successfully colonized caves, especially in Europe and the United States. Troglobites are often highly modified; they are larger and paler, the eyes are reduced or absent, and the appendages are attenuated. Soil inhabitants are usually small, whereas troglodytes may be 5 mm in length.
About 15 genera are recognized, but the most common being Neobisium, Roncus, and Microcreagris.

SYARINIIDAE

The venom apparatus occurs only in the fixed finger of the palpal chela. The pleural membranes of the abdomen may be granulate, but usually are smoothly and longitudinally striate. The line of articulation between the basifemur and the telofemur of leg IV at least slightly oblique to the long axis of the femur. The terminal (t) trichobothrium of the movable chelal finger is shortened and lanceolate toward the distal end, a unique feature among pseudoscorpions. The carapace is rectangular, with four eyes or none. The chelicera may bear a long, slender, simple galea, or none. The palpal chela has the usual 12 trichobothria.
This family is found mainly in the Northern Hemisphere; there are a few forms in Africa and southeastern Asia. They live in soil and litter, and a few have become successful cavernicoles, for example, Troglobisium and Pseudoblothrus in Europe and Chitrella in the United States. The widespread tropical Ideobisium belongs in this family, although it has usually been placed in the Neobisiidae. As in the Neobisiidae, soil dwellers may be tiny, and troglobites range up to 5 mm in length.
About 12-15 genera can be assigned to this family, the most common being Syarinus, Chitrella, Pachychitra, and Ideobisium.

IDEORONCIDAE

A well-developed venom apparatus is present in both finger of the palpal chela, and there are many more than 12 trichobothria on the chela. The trichobothria are variable in size, and difficult to count exactly, but there is always a group of three or four conspicuous ones on the dorsum of the hand. The pleural membranes of the abdomen are smoothly, longitudinally striate. The femur of leg IV is usually short and stout, with the line of articulation between the basifemur and the telofemur near the middle, and perpendicular to the long axis. The carapace is longer than broad. There are two eyes or none. The chelicera has a long, slender, simple galea. The arolia of the pedal tarsi are usually longer than the claws, and often bifid.
This is mainly a tropical family, with most species occurring in Middle America, Africa, and southeastern Asia, but some extending into temperate areas of the United States and South America. Most live in litter or under rocks, often in arid regions, although some inhabit rain forests; a few are cavernicolous and highly modified.
There are 8 recognized genera, of which Ideoroncus and Albiorix are the most common.

HYIDAE

This family and the Bochicidae are problematical groups, the relationships within and between which have not been fully worked out. As described by J. C. Chamberlin, this family was based on the genus Hya from the Philippines and Indonesia. The venom apparatus is well developed in both fingers of the palpal chela. The usual 12 trichobothria are on the chela, with the internal basal (ib) trichobothrium on the dorsum of the hand at the base of the fixed finger. The pleural membranes are granulate or granulostriate. The chelicera has a long, slender, simple galea and a unique flagellum with six or seven slenderly clavate and distally deeply incised blades. The marginal teeth of the fixed chelal fingers are widely spaced; those of the movable finger are nearly obsolete. The subterminal tarsal setae are acuminate.
This diagnosis applies to the 2 species of the genus Hya and perhaps also to Indohya from India, Parahya from the Caroline Islands, and Stenohya from Vietnam, as proposed by M. Beier. However, the American forms which have been placed here by various authors are, for a number of reasons, more appropriately placed in the Bochicidae.

BOCHICIDAE

This family, like the Hyidae, is poorly understood, but may be used to accommodate several Middle American and West Indian genera which were previously placed elsewhere. As originally described by J. C. Chamberlin, it was a subfamily of the Ideoroncidae, based upon Bochica from Grenada, West Indies, with the following characteristics: The venom apparatus is well developed in both fingers of the palpal chela. The usual 12 trichobothria are present on the chela, with the internal basal (ib) trichobothrium on the dorsum of the hand near the middle. The chelicera has a long, slender, simple galea and a flagellum of two to four small, spinulated setae. The marginal teeth of both chelal fingers are distinct and contiguous. The subterminal tarsal setae are denticulate.
Tentatively, the following genera can be placed here, in addition to Bochica, even though some have characters at variance with some of those listed above: Leucohya and Troglohya, from caves in Mexico; Apohya, from Mexico; Mexobisium, from Middle America and Cuba; Antillobisium, from caves in Cuba; and an undescribed genus from a cave in Jamaica.

VACHONIIDAE

The carapace is longer than broad, and lacks eyes. The venom apparatus is developed only in the movable finger of the palpal chela; the venom duct is long. The tip of the fixed finger is blunt and bears several teeth. The internal basal (ib) trichobothrium is isolated on the dorsum of the chelal hand, near the middle. The chelicera has a long, slender, simple galea and a flagellum of three or four short, denticulate setae. The line of articulation between the basifemur and the telofemur of leg IV is oblique to the long axis of the femur. The claws on the legs are simple.
These pseudoscorpions have been found only in caves in Mexico and Central America. Al species are obviously highly modified troglobites; they are large and pale and have attenuated appendages.
Members of this family are certainly related closely to the Bochicidae, and further study may show that they actually belong in that family. Meanwhile, 2 genera, Vachonium and Paravachonium, are included here.

GYMNOBISIIDAE

This group, formerly considered by many authors to be a subfamily of the Vachoniidae, is actually quite distinct, possessing the following characteristics: The carapace is almost square when viewed from above. There are usually four eyes. A venom apparatus is present only in the movable finger of the chela. The venom duct is short. The fixed finger has terminal teeth arranged into a sheathing device for the venom tooth of the movable finger. The internal basal (ib) trichobothrium is at the base of the fixed chelal finger, with three other trichobothria. The chelicera has a branched galea and a flagellum of six to eight long setae, some terminally denticulate. The line of articulation between the basifemur and the telofemur of leg IV is perpendicular to the long axis of the femur. Each pedal claw has a small denticle on the outer margin, toward the base.
Four genera are included in the family: Gymnobisium, from South Africa; Mirobisium and Vachonobisium, from Argentina, Bolivia, and Chile; and Beierobisium, from the Falkland Islands. They are generally small, and inhabit soil and litter.