Prismognathus formosanus Nagel, 1928

(Figs. 102, 130, 143, 197, 223, 235)

Prismognathus formosanus Nagel, 1928: 274 [type locality: monte Morrison (Yushan, central Taiwan)], Fig. 2, male; Sakaino 1992: 10 –11, localities, Figs. 6–10, males and female; Fig. 12, aedeagus; Mizunuma & Nagai 1994: plate 51, Figs. 232 (1–8), males and female; Fujita 2010: 163, plate 98, Figs. 483-1–3.

Prismognathus piluensis: Fujita 2010: 163, plate 98, partim [Figs. 484-3, 484-4 for specimens from Anmashan]. Misidentification.

Material examined. CHINA: Taiwan: 4 3, 3 ƤƤ, Nantou, Sungkang, VIII.2003 -2007; 5 3, 3 ƤƤ, Nantou, Hewangshan, VII.2001 -2004; 8 3, 6 ƤƤ, Taichung, Anmashan, VIII.2005 -2009.

Identification. This species was described on a single male from Yushan, central Taiwan, characterized by the double subbasal teeth along the ventral ridge, a large gap between subbasal teeth and the median teeth on the mandible, the obtuse anterolateral angles of the head, and the strongly swollen postocular margins of the head. It is easily distinguished from the sympatric P. davidis, but is difficult to separate from the nearby P. piluensis .

The separation of P. formosanus and P. piluensis is problematic. Prismognathus piluensis was originally described from Pilu, eastern Taiwan, with the following differences in comparison with P. formosanus: the surface of the male head “more strongly punctuate”, the outer margin of the male mandible partly concave, the inner margin of the male mandible straighter, the median teeth of the male mandible larger in number, the subbasal teeth of the male mandible less protruding, and the body of the female more black and stout. However most of these differences vanish when more specimens are examined. Some male specimens from Anmashan, central Taiwan have the most above-mentioned characters in common with the males of P. piluensis and have been identified as P. piluensis by some collectors and researchers (Fujita 2010), however the examination of the male and female genitalia of this population prove them to be P. formosanus .

It is possible that P. piluensis is only restricted to the type locality and the very nearby area in eastern Taiwan. It is a pity that we have not been able to examine any specimen from Pilu.

Taxonomic notes. P. formosanus is more close to P. triapicalis than to any other species from the continent. The relationship between P. formosanus and P. piluensis is unclear at present.

Distribution. Central Taiwan.

Prismognathus piluensis Sakaino, 1992 (doubtful species) (Fig. 235)

Prismognathus piluensis Sakaino, 1992: 11 [type locality: Pilu, Hualien-Hsien (eastern Taiwan)], Figs. 1-5, males and female; Fig. 11, aedeagus; Mizunuma & Nagai, 1994: plate 51, Figs. 233 (1–2); Fujita 2010: 163, plate 98, partim [Figs. 484-1, 484-2, specimens from Pilu]

Material examined. None

Identification. As discussed above, this species could be a synonym of P. formosanus . Specimens from Pilu need to be examined to verify this hypothesis.

Distribution. Eastern Taiwan (Pilu of Hualien).