A review of the pseudoscorpion genus Ideoblothrus (Pseudoscorpiones, Syarinidae) from western and northern Australia

Five new pseudoscorpion species belonging to the genus Ideoblothrus are named and described from Western Australia and the Northern Territory: I. pisolitus from a single pisolitic mesa near Pannawonica, I. nesotymbus from limestone karst on Barrow Island, I. westi from limestone karst near the Fortescue River, I. descartes from a vine thicket on Descartes Island in the Kimberley, and I. milikapiti from rainforest on Melville Island. New specimens of I. papillon Harvey from Papillon Cave and I. woodi Harvey from Cave C‐167, Western Australia are recorded. A further species is recognised but not named as adult specimens are not available: Ideoblothrus sp. ‘Mesa A’ occurs within a different pisolitic mesa than I. pisolitus.


Introduction
The pseudoscorpion genus Ideoblothrus was first named by Balzan (1892) as a subgenus of Ideobisium Balzan, 1892, with a single included species, Ideobisium (Ideoblothrus) similis Balzan, 1892 from Petare, Miranda Province, Venezuela. The name Ideoblothrus languished as a synonym of Ideobisium until resurrected by Muchmore (1982) who revalidated the name, elevated it to generic level and provided a modern description of the genus and the type species. He also transferred many other species of Ideobisium to Ideoblothrus and demonstrated that the two genera, although sharing several similarities, could be reliably distinguished from each other based on a variety of morphological features. Muchmore (1982) also compared Ideoblothrus with Pachychitra Chamberlin, 1938, originally named for a cave-dwelling species from Yucatán, Mexico (Chamberlin 1938) with a further nine species named and described from across the Central America and the Caribbean region (Hoff 1945(Hoff , 1964Wagenaar-Hummelinck 1948;Muchmore 1972Muchmore , 1979. He concluded The material examined for this study is lodged in the Western Australian Museum, Perth (WAM). Terminology and mensuration mostly follows Chamberlin (1931), with the exception of the nomenclature of the pedipalps, legs, and with some small modifications to the terminology of the trichobothria (Harvey 1992). The following abbreviations are used in the illustrations for the carapaceal setal rows: an, anterior row; oc, ocular row; me, median row; in, intermediate row; po, posterior row. This system is slightly modified from that employed by Gabbutt (1965) and Gabbutt and Vachon (1965, 1967, 1968 for the Neobisiidae. The following abbreviations are used in the illustrations for the male genitalia, largely following Legg (1975): ejca, ejaculatory canal atrium; gls, glandular setae; lgs, lateral genital sac; mgs, median genital sac.
The specimens were studied using temporary slide mounts which were prepared by immersion of specimens in 25% lactic acid at room temperature, and mounting them on microscope slides with 10 or 12 mm coverslips supported by small sections of 0.25, 0.35, or 0.50 mm diameter nylon fishing line. After study the specimens were washed in distilled water and returned to 75% ethanol with the dissected portions placed in 12 6 3 mm glass genitalia microvials (BioQuip Products). All specimens were studied using an Olympus BH-2 compound microscope and illustrated with the aid of a drawing tube. Measurements were taken at the highest possible magnification using an ocular graticule. Photographs of whole animals were taken using a Micropublisher 5.0 digital camera mounted on a Leica MZ16 microscope; multiple images were combined using Auto-Montage by Syncroscopy (version 4.01).
We have directly compared the five new species of Ideoblothrus with the published descriptions of all previously known members of the genus to ensure that they have not been previously named. In the diagnoses, however, we have limited our comparisons to the previously name Australasian species, utilising the following descriptions: Daday (1897), Table I. Named species of Ideoblothrus and their recorded distributions.

Diagnosis
Species of Ideoblothrus can be distinguished from the morphologically similar genus Ideobisium by the following features, following Muchmore (1982): eyes completely absent (two pairs of eyes present in Ideobisium); pleural membrane granulo-striate near cephalothorax, remainder longitudinally striate (Muchmore stated that Ideoblothrus has entirely smooth pleural membranes) (granulate anteriorly, becoming longitudinally granulo-striate or smoothly striate posteriorly in Ideobisium); trichobothria ib, isb, esb, and eb positioned in an oblique row near base of fixed finger (positioned near middle of hand and isb on external side of hand near base of fixed finger in Ideobisium); pedipalpal segments mostly smooth but with fine granules on flexor side of femur, patella, and chelal hand (entirely smooth in Ideobisium); suture between femur IV and patella IV not indented on dorsal margin (indented in Ideobisium); arolium as long as or slightly longer than claws (arolium shorter than claws in Ideobisium); internal genital setae of the male arranged in two triangular groups of three (two parallel longitudinal rows of three in Ideobisium); median genital sac of the male genital system of Ideoblothrus species composed of single sac (distinctly bipartite in Ideobisium).
Ideoblothrus is also very similar to Microblothrus Mahnert, 1985, known by M. tridens Mahnert, 1985 from Amazonian Brazil, which was distinguished from Ideoblothrus by the lack of trichobothria isb and sb.
Ideoblothrus can be distinguished from the other genera currently included in the Syarinidae as follows. Syarinus Chamberlin, 1930 andAnysrius Harvey, 1998 (Syarininae) possess a much-reduced femur of legs III and IV, and the suture between the femur and patella is strongly oblique (femur not reduced in size, and suture slightly oblique to long axis in Ideoblothrus). Trichobothrium ib is located on the chelal fingers in Ideoblothrus, Microblothrus, but is situated on the dorsal margin of the chelal hand basal to the level of eb and esb in Aglaochitra Chamberlin, 1952, Alocobisium Beier, 1952, Chitrella Beier, 1932, Chitrellina Muchmore, 1996, Hadoblothrus Beier, 1952, Microcreagrella Beier, 1961, Microcreagrina Beier, 1961, Pseudoblothrus Beier, 1931, and Nannobisium Beier, 1931.

Description
The description presented by Muchmore (1982) requires no modification except for: Pedipalp: robust, segments usually less than 3.0 times longer than broad, but more than 3.0 times longer than broad in troglobitic species.
Male genitalia: median genital sac composed of single ovoid sac.

Description
Deutonymph. Colour: generally pale, pedipalps pale yellow orange. Chelicera: with five setae on hand, all setae acuminate; movable finger with one subdistal seta; flagellum of five blades, distal blade broadened and finely denticulate; serrula exterior with ca 17 blades.
Pedipalp: trochanter 1.57, femur 2.77, patella 2.31, chela (with pedicel) 3.21, chela (without pedicel) 3.03, hand 1.49 times longer than broad, movable finger 1.11 times longer than hand. Fixed chelal finger with six trichobothria, movable chelal finger with two trichobothria ( Figure 5): esb, isb, sb, and st absent; eb situated at base of fixed finger; ib situated on dorso-distal surface of hand; ist and est situated close together; it situated distally to est and ist; et situated sub-distally; b situated sub-basally; t situated sub-medially; t slightly shortened, lanceolate, and bent backward. Venom apparatus only present in fixed chelal finger. Chelal teeth: fixed finger with 22 slightly retrorse teeth, tooth row ending just distal to it; movable finger with 32 rounded teeth, tooth row extending midway between t and b.
Dimensions ( Chelicera: with four setae on hand, all setae acuminate; movable finger without subdistal seta; flagellum not visible in preparation; serrula exterior with ca 14 blades. Pedipalp: trochanter 1.35, femur 2.45, patella 2.17, chela (with pedicel) 3.35, chela (without pedicel) 3.17, hand 1.53 times longer than broad, movable finger 1.13 times longer than hand. Fixed chelal finger with three trichobothria, movable chelal finger with one trichobothrium ( Figure 6): isb, esb, sb, st, est, ist, b, and it absent; eb situated at base of fixed finger; ib situated on dorso-distal surface of hand; et situated sub-distally; t situated medially on movable finger; t bent backwards, but not lanceolate. Venom apparatus only present in fixed chelal finger. Chelal teeth: fixed finger with 12 slightly retrorse teeth, tooth row ending distally to et; movable finger with 22 rounded teeth, tooth row extending to t.

Remarks
This species is known only from Cave C-167 situated on Cape Range peninsula. Due to a typographical error, Harvey (1991b) incorrectly reported that the width of the chela in the male of I. woodi is 0.21 mm; the correct width is 0.27 mm.
Very few protonymphs of the family Syarinidae have been described. The protonymphs of Ideobisum caecum Mahnert, 1979 (now Ideoblothrus caecus) from Brazil (Mahnert 1979) and Anysrius chamberlini Harvey, 1998 from Tasmania (Harvey 1998) were described and the trichobothrial pattern illustrated, but neither recorded or illustrated the morphology of trichobothrium t. Mahnert (1985b) illustrated the trichobothrial pattern of Microblothrus tridens Mahnert, 1985 from Brazil and showed that trichobothrium t is distinctly lanceolate. The protonymph of I. woodi has an acuminate trichobothrium t, quite unlike the morphology of the deutonymph and adults. Whether this pattern is more widespread throughout the family remains to be seen through the examination of more protonymphs.

Etymology
The specific epithet refers to the presence of this species within Mesa B, which is formed from pisolite.

Diagnosis
Ideoblothrus pisolitus differs from all other species of the genus by the noticeably more slender pedipalpal patella and chela, which are 2.22-2.26 ("), 2.08-2.27 (R) and chela (with pedicel) 3.36-3.47 ("), 3.07 (R) times longer than broad, respectively. In addition, I. pisolitus has only four setae in the intermediate row of the carapace, which are situated near the lateral margins of the carapace.
Genitalia: male genitalia with small rounded ejaculatory canal atrium; moderately sized lateral genital sacs and an undivided, enlarged median genital sac ( Figure 19); male internal genital setae arranged in two triangular groups of three; pair of setae surrounding an anteromedian notch of the posterior genital operculum; single, ovoid median genital sac. Female genitalia ( Figure 21) with single, broad median cribriform plate, and one pair of slender lateral median cribriform plates.
Legs (Figures 12, 13): femora I and II longer than patellae I and II; femora I and II with one transverse lyrifissure situated sub-distally; femur + patella of leg IV 3.74 ("), 3.88 (R) times longer than broad; legs III and IV with articulation between femur and patella segments slightly oblique; tibiae III and IV with medial tactile seta; metatarsi III and IV with sub-basal tactile seta; diplotarsate, all legs with tarsus longer than metatarsus; subterminal tarsal setae distally serrate; arolia same length as claws, not divided; claws simple.

Tritonymph. Morphology generally as in adults.
Colour: all sclerotised portions pale red-orange, rest of body pale yellow-brown. Chelicera: with five setae on hand, all setae acuminate; movable finger one sub-distal seta; galea straight and extends past tip of finger but not extending to tip of galeal seta; flagellum of five blades, distal blade broadened and finely denticulate; serrula exterior with ca 22 blades.
Pedipalp: internal margins of femur, patella, and chela with light granulations, setae on internal margins very long and acicular; femur without tactile setae; trochanter 2.04, femur 3.06, patella 2.19, chela (with pedicel) 3.17, chela (without pedicel) 2.94, hand 1.58 times longer than broad, movable finger 0.91 times longer than hand. Fixed chelal finger with seven trichobothria, movable chelal finger with three trichobothria (Figure 11): isb and sb absent; eb and esb situated at base of fixed finger; ib situated on dorso-distal surface of hand; ist and est situated close together, et situated sub-distally; b situated sub-basally; st and t situated sub-distally, t lanceolate, slightly shortened, and bent backward. Venom apparatus only present in fixed chelal finger, venom duct very short, nodus ramosus inflated. Chelal teeth: fixed finger with ca 29 rounded teeth; movable finger with ca 38 rounded teeth.
Legs: femur I longer than patella I; metatarsi and tarsi not fused; arolium same length as claws, not divided.

Remarks
Ideoblothrus pisolitus has only been found within one iron-bearing pisolite mesa, approximately 173 ha in area, in the Pannawonica region of Western Australia. Three males, two females, and one tritonymph were collected from three boreholes using leaflitter baited traps placed at depths of 10-40 m.

Description
Deutonymph. Colour: generally pale, pedipalps and chelicera very pale yellow orange. Chelicera: with five setae on hand, all setae acuminate; movable finger one sub-distal seta; flagellum of five blades, distal blade broadened and finely denticulate; serrula exterior with ca 17 blades.
Pedipalp: trochanter 1.60, femur 2.93, patella 2.29, chela (with pedicel) 3.32, chela (without pedicel) 3.12, hand 1.58 times longer than broad, movable finger 1.03 times longer than hand. Fixed chelal finger with six trichobothria, movable chelal finger with two trichobothria (Figure 7): isb, sb, esb, and st absent; eb situated at base of fixed finger; ib situated on dorso-distal surface of hand; ist and est situated close together; it situated distally to est and ist; et situated sub-distally; b situated sub-basally; st situated sub-medially. Venom apparatus only present in fixed chelal finger. Chelal teeth: fixed finger with 18 rounded teeth, tooth row ending basally to et; movable finger with 27 rounded teeth, tooth row extending midway between st and b.

Remarks
A single deutonymph was collected from Mesa A situated approximately 7.6 km from Mesa B, the only known location of I. pisolitus. Due to the lack of adult specimens we cannot be sure of its identity. However, it is possible that it represents a distinct taxon, making it consistent with patterns found in other troglobitic organisms present within these pisolitic formations. In particular, molecular studies have shown Mesa A and Mesa B to contain distinct species of the schizomid genus Draculoides (O. Berry, unpublished data).

Etymology
The specific epithet refers to the occurrence of this subterranean species on Barrow Island (nesos, Greek, island; and tymbos, Greek, tomb).

Diagnosis
Ideoblothrus nesotymbus is substantially larger than most other Australasian species [e.g. pedipalpal patella length 0.45-0.50 mm ("), 0.53-0.56 mm (R)], including I. descartes, I. westi, I. milikapiti, I. pugil, I. ceylonicus, I. palauensis, and I. bipectinatus which are all substantially smaller (e.g. pedipalpal patella length less than 0.33 mm). Ideoblothrus nesotymbus differs from I. pisolitus in the shape of the pedipalpal chela which is noticeably more slender in I. pisolitus. It differs from I. pugil robustus in being slightly larger [e.g. pedipalpal patella length 0.42 mm (R)]. It differs from I. woodi by the length of the male galea, which is relatively long in I. nesotymbus and much reduced in I. woodi. It differs from I. papillon by the slightly less slender pedipalpal chela, which is 2.59 ("), 2.69-2.92 (R) times longer than broad in I. nesotymbus and 2.83 ("), 3.00 (R) times longer than broad in I. papillon.
Genitalia: male genitalia, identical to I. pisolitus, apart from internal genital setae arranged in a triangular group of three setae and a group of four setae: pair of setae on edge  Legs: femora I and II longer than patellae I and II; femora I and II with one transverse lyrifissure situated sub-distally; femur + patella of leg IV 2.68 ("), 2.98 (R) times longer than broad; legs III and IV with articulation between femur and patella segments slightly oblique; tibiae III and IV with medial tactile seta; metatarsi III and IV with sub-basal tactile seta; diplotarsate, all legs with tarsus longer than metatarsus; subterminal tarsal setae distally serrate; arolia same length as claws, not divided; claws simple.

Remarks
Ideoblothrus nesotymbus has only been found at three locations within limestone karst on Barrow Island. One male and three females were collected from boreholes using leaf-litter baited traps placed at depths of 5-46 m.

Etymology
This species is named for Paul West, collector of the holotype.

Diagnosis
Ideoblothrus westi is amongst the smallest species of the genus [e.g. pedipalpal patella 0.30 mm (R)] and, amongst the Australasian species, is of similar size to I. descartes and I.
pugil (e.g. pedipalpal patella 0.30-0.32 mm). It is larger than I. milikapiti, I. palauensis, and I. bipectinatus (e.g. pedipalpal patella 0.20-0.22 mm). Ideoblothrus westi differs from similarly sized species of the genus by the shape of the pedipalpal chela, which is rather stout and the externo-basal margin of the chelal hand is distinctly angulate.

Description
Adult female. Colour: pedipalps reddish brown, legs pale yellow brown, rest of body pale yellow. Chelicera ( Figure 32): five setae on hand, all setae acuminate, is very long, ls, sbs, bs, and es short; movable finger with one sub-distal seta; fixed finger with ca eight teeth; movable finger with ca four teeth; with two dorsal lyrifissures and one ventral lyrifissure; galea long, slightly curved and extends to tip of galeal seta; flagellum of five blades, distal blade broadened and finely denticulate; serrula exterior with ca 15 blades.
Pedipalp (Figure 30): mostly smooth, with only the internal margins of patella and chela with sparse fine granulations; setae on internal margins very long and acicular; trochanter without tubercles; trochanter 1.80, femur 2.69, patella 2.00, chela (with pedicel) 2.60, chela (without pedicel) 2.50, hand 1.35 times longer than broad, movable finger 0.82 times longer than hand. Femur without tactile setae; without basal projection. Patella with one lyrifissure situated dorsally near pedicel. Fixed chelal finger with eight trichobothria, movable chelal finger with four trichobothria (Figure 31): eb and esb situated close together on lateral margin of hand, isb situated medially at base of finger, slightly basal to ib; est situated near ist and it; et sub-distal; single sensory pit between sb and st; microsetae (chemosensory setae) absent on both fingers; trichobothrium b of movable finger situated sub-basally; sb, st, and t situated medially, close to each other; t lanceolate, slightly shortened, and bent backward. Venom apparatus present only in fixed chelal finger, venom duct very short, nodus ramosus inflated. Chelal teeth of both fingers with flattened edges; fixed finger with 13 teeth, tooth row terminating slightly basal to et; movable finger with ca 27 teeth; accessory teeth absent. External and internal chelal condyles small and rounded.
Genitalia: female genitalia not visible in preparation. Legs (Figures 33, 34): femora I and II longer than patellae I and II; femora I and II with one transverse lyrifissure situated sub-distally; femur + patella of leg IV 2.92 times longer than broad; legs III and IV with articulation between femur and patella segments slightly oblique; tibiae III and IV with one medial and one sub-distal tactile seta; metatarsi III and IV with subbasal tactile seta; diplotarsate, all legs with tarsus longer than metatarsus; subterminal tarsal setae distally serrate; arolia slightly longer than claws, not divided; claws simple.

Etymology
The specific epithet is a noun in apposition taken from the type locality, Descartes Island. This island was originally named for the famed French philosopher, mathematician and scientist, René Descartes (1596-1650).

Description
Adults. Colour: pedipalps red orange, carapace, chelicera, and coxae yellow orange, rest of body pale yellow. Chelicera: five setae on hand, all setae acuminate, is, ls, sbs, and bs long, es very short; movable finger with one sub-distal seta; fixed finger with ca 10 teeth; movable finger with six teeth; with two dorsal lyrifissures and one ventral lyrifissure; male galea short, only very slightly curved and not extending to tip of galeal seta; female galea long, curved and extends to tip of galeal seta; flagellum of five blades, distal blade broadened and finely denticulate; serrula exterior with 21-23 ("), 22 (R) blades.
Genitalia: male genitalia, as far as can be discerned, identical to I. pisolitus; internal genital glandular setae arranged in two triangular groups of three; pair of setae on edge of sternite III surrounding the antero-median notch of the posterior genital operculum. Female genitalia with single, broad median cribriform plate, and one pair of slender lateral median cribriform plates.
Legs: femora I and II longer than patellae I and II; femora I and II with one transverse lyrifissure situated sub-distally; femur + patella of leg IV 2.64 ("), 2.73 (R) times longer than broad; legs III and IV with articulation between femur and patella segments slightly oblique; tibiae III and IV with medial tactile seta; metatarsi III and IV with sub-basal tactile seta; diplotarsate, all legs with tarsus longer than metatarsus; subterminal tarsal setae not distally serrate; arolia same length as claws, not divided; claws simple.
Dimensions ( Figure 44): eb, esb, isb, and ib forming an arc on baso-lateral margin of hand; isb situated slightly distally to ib; ist, est, and it situated close together; et sub-distal; two small lanceolate setae present on fixed chelal finger, one situated near esb and another between isb and est; microsetae (chemosensory setae) absent on both fingers; trichobothrium b of movable finger situated sub-basally; sb, st, and t situated medially, close to each other, st and t nearly touching and separated by less than one areolar diameter; t lanceolate, slightly shortened, and bent backward. Venom apparatus present only in fixed chelal finger, venom duct very short, nodus ramosus inflated. Chelal teeth of both fingers with flattened edges; fixed finger with 20-21 teeth; movable finger with ca 27-29 teeth; accessory teeth absent. External and internal chelal condyles small and rounded.
Genitalia: male genitalia, as far as can be discerned, identical to I. pisolitus, apart from a smaller medial genital sac; pair of setae on edge of sternite III surrounding the anteromedian notch of the posterior genital operculum; internal genital glandular setae arranged in two triangular groups of 3.
Legs: femora I and II longer than patellae I and II; femora I and II with one transverse lyrifissure situated sub-distally; femur + patella of leg IV 3.00 times longer than broad; legs III and IV with articulation between femur and patella segments slightly oblique; tibiae III and IV with one medial and one sub-distal tactile seta; metatarsi III and IV with medial tactile seta; diplotarsate, all legs with tarsus longer than metatarsus; subterminal tarsal setae not distally serrate; arolia slightly shorter than claws, not divided; claws simple.

Remarks
Ideoblothrus milkapiti is known from a single location on Melville Island in the Northern Territory (Figure 1).

Discussion
The description of five new species of Ideoblothrus from western and northern Australia brings the total number of species in this genus to 41, with seven Australian species. Further species are known from Queensland, but have not been studied as part of this study, and they remain unnamed. Ideoblothrus is the largest genus of Syarinidae, and is also the third largest neobisioid genus, surpassed only by Neobisium with 216 species and Roncus with 115 species. It has the most widespread distribution of any neobisioid genus and is known from all tropical and subtropical regions of the world (Table I). It is difficult to postulate on historical scenarios that might have led to this cosmo-tropical distribution but the options include recent dispersal or a widespread Pangean distribution overlayed with vicariance.
Of the seven named Australian species, five occur within subterranean habitats, and all are from the semi-arid and arid zones of Western Australia. The only other subterranean species of Ideoblothrus occur in Mexico (Chamberlin 1938;Muchmore 1972), and all of these are no doubt the result of separate incursions into the subterranean milieu.
All of the Australian species of Ideoblothrus can be regarded as short-range endemic species as defined by Harvey (2002). All seven species have highly localised distributions and they occur in discontinuous habitats. Ideoblothrus papillon and I. woodi occur in caves on Cape Range Peninsula, I. pisolitus and I. nesotymbus (as well as I. sp. ''Mesa A'') occur in other subterranean cavities, and I. descartes and I. milikapiti occur in rainforest thickets. This pattern is very similar to the distribution of the other neobisioid family found throughout the region, the Hyidae (Harvey 1993, forthcoming). Epigean species of Indohya occur throughout the Kimberley rainforests, with troglobitic species occurring in the Cape Range Peninsula (I. humphreysi and I. damocles) and the Kimberley region (I. napierensis and I. gollum).