Ideoblothrus Balzan, 1892

Harvey, Mark S. & Edward, Karen L., 2007, A review of the pseudoscorpion genus Ideoblothrus (Pseudoscorpiones, Syarinidae) from western and northern Australia, Journal of Natural History 41 (5 - 8), pp. 445-472 : 449-450

Ideoblothrus Balzan

Ideobisium (Ideoblothrus) Balzan 1892, p 541 . Pachychitra Chamberlin 1938, p 111 ; Hoff 1945, p 1; Hoff 1964, p 7–8; Muchmore 1979, p 195 (synonymised by Muchmore 1982, p 207). Ideoblothrus Balzan : Muchmore 1982, p 207; Harvey 1991a, p 421; Harvey 1991b, p 495.

Type species. Ideobisium (Ideoblothrus) : Ideobisium (Ideoblothrus) similis Balzan, 1892 , by subsequent designation of Muchmore (1982).

Pachychitra : Pachychitra maya Chamberlin, 1938 , by original designation.

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 and Anysrius 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.

Pleural membrane: finely, longitudinally striate, but occasionally granulo-striate within cephalothorax.

Male genitalia: median genital sac composed of single ovoid sac.

Remarks

Our observations on the male genital system of several different syarinids indicate that there is substantial variation in the morphology of the median genital sac. Species of Ideoblothrus bear a single ovoid median genital sac, which we have observed in several Australian species, I. aeoodi ( Harvey 1991b, Figure 33 ), I. papillon ( Harvey 1991b) , I. pisolitus , I. nesotymbus , I. milikapiti , and I. descartes , as well as I. sp. from Colombia (WAM T65473). This morphology contrasts strongly with that found in species of Ideobisium which have a strongly bipartite median genital sac, confirmed in I. puertoricense Muchmore, 1982 from Puerto Rico (WAM T68624) and I. sp. from New Caledonia (WAM, not registered). The bipartite morphology also occurs in several other syarinids, including Aglaochitra Chamberlin, 1952 , Pseudoblothrus Beier, 1931 , and Chitrella Beier, 1932 (e.g. Chamberlin 1952; Vachon 1952, 1954, 1969; Mahnert 1980, 1990; Inzaghi 1983; M. S. Harvey, unpublished data).

Figures

Figures 29–35. Ideoblothrus aeesti sp. nov., holotype ♀. (29) Carapace. (30) Right pedipalp, dorsal. (31) Left chela, lateral. (32) Left chelicera, dorsal. (33) Leg I. (34) Leg IV. (35) Coxal region, ventral. Scale bars: 0.2 mm (29–31, 35); 0.1 mm (32–34).