Genus Idister Marseul, 1880


Idister Marseul, 1880 [type species: Idister (Idister) morphon Marseul, 1880: 154].


Notes (Ohara & Mazur, 2000).

Idister was erected by Marseul in 1888 for a single species, I. morphon from Sumatra. Marseul emphasized the structure of hind legs (Fig. 4H) as representing important generic characteristics, apical margin of metatibia with two small carinae that are densely furnished with small denticles and the metatarsi densely covered by long silken hairs. Lewis (1892) added a new species, I. gestroi from Burma, to the genus, with, however, some hesitation. In 1989 Mazur added two new species, I. omalodellus and I. platysomoides, dividing the genus into two subgenera, Idister and Diister.

According to our detailed examinations of the species belonging here (except I. gestroi), the genus Idister is rather heterogeneous as mentioned below, and it contains also a variable undescribed species from New Guinea. The species included here might not be congeneric and should be revised and rearranged.

Distribution (as temporary stated). Southeast Asia (Bruma, Sumatra, Enggano Is., Mentawei Is., Borneo, New Guinea).


Subgenus Idister Marseul, 1880

Notes (Ohara & Mazur, 2000).

Idister Marseul contains two species, I. morphon and I. gestroi, and differs from the subgenus Diister Mazur in the outline of body more oval, the protibia without distinct tooth, the anterior tarsus with dense ventral pilosity, and the metatibia dilated and without distinct denticulation on outer edge (Mazur, 1989).

The structure of the male genital segments of I. morphon (Fig. 5) is so peculiar that it is quite difficult to find relationships between the subgenus Diister and other members of the tribe Platysomatini.

Distribution. Burma, Sumatra, Enggano Is., Mentawei Is., Borneo.


  • Idister (Idister) morphon Marseul, 1880
  • Idister (Idister) mendax Lewis, 1906

  • Subgenus Diister Mazur, 1989

    Diister Mazur, 1989: 735 [type species: Idister (Diister) omalodellus Mazur, 1989: 735].

     

    Notes (Ohara & Mazur, 2000).

    Diister is represented by two species, I. (D.) omalodellus and I. (D.) platysomoides both from New Guinea. It may be characterized by outline of body being more elongate, protibia normally toothed, anterior tarsus without dense ventral pilosity, and metatibia less dilated, with distinct denticulation on outer edge (Mazur, 1989).

    Because these species have normal hind tibiae and tarsi, Diister may be ranked up to the generic level.

    In both species, I. omalodellus and I. platysomoides, the structures of male genitalia and pygidia and the shapes of protibiae are very diverse (Fig. 6-9). On the other hand, the presence of the transverse striae of first two abdominal sterna is common to both species and may be an apomorphic character. There is no doubt that we have only fragmentary material from New Guinea. The systematic study of the genus is in need of further work.

    Distribution. New Guinea.



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