Genus Pseudohercostomus Stackelberg

(Fig. 38 A–F)

Pseudohercostomus Stackelberg, 1931: 776. Type species: Pseudohercostomus echinatus Stackelberg [Oriental], by original designation.

Remarks. Stackelberg (1931) erected this genus for the Oriental species P. echinatus. Negrobov (1988) described a second species, P. allini Negrobov from Chile, and recently Yang & Grootaert (1999) described a third species, P. s i n e n s i s Yang & Grootaert, from Oriental China. Dyte & Smith (1980) also recorded the genus from the Afrotropical Region. Stackelberg (1931) placed Pseudohercostomus in the Dolichopodinae even though it has a bare scape and an encapsulated, non­pedunculate hypopygium. This subfamily placement has been followed by subsequent authors including Parent (1934c), Negrobov (1980), Ulrich (1981), Yang & Grootaert (1999) and Yang et al. (2001).

The systematic position of Pseudohercostomus is currently unclear. Although P. echinatus was excluded from the Dolichopodinae in the analysis, this species shows a number of similarities to certain species of Oriental Paraclius (e.g., P. abbreviatus) and Afrotropical Pelastoneurus (e.g., P. diversifemur) including the possession of dense surface setae on the anterior portion of the thorax, and the apical position of the lateral seta on the hind coxa. The latter two features; however, could not be coded into discrete states due to the presence of numerous intermediates encountered among the examined exemplars. Grichanov (2004) also recognized the similarity between Pseudohercostomus echinatus and certain Afrotropical species of Pelastoneurus and proceeded to synonymize Pseudohercostomus with Pelastoneurus Loew (= Paracleius Bigot). However, as a result of Grichanov’s (2004) alternate interpretation of the nomenclature involving the names Paracleius Bigot, Pelastoneurus Loew and Paraclius Loew, and the recent suppression of Paracleius Bigot by the I.C.Z.N. (2004), his synonymy of Pseudohercostomus with Pelastoneurus Loew (= Paracleius Bigot) must be rejected as Pseudohercostomus echinatus is clearly not congeneric with Pelastoneurus in the sense of the type species Pelastoneurus vagans.

Bickel (pers. comm.) has also suggested a possible relationship between Pseudohercostomus and the enigmatic New World genus Keirosoma Van Duzee. I have examined specimens of K. albicinctum Van Duzee (CNC) and agree that these genera may be related as they share several features including a bulky habitus, similar wing venation with R4+5 and M slightly divergent, apical position of the lateral seta on the hind coxa (but see comments above), segment 7 of the male genitalia entirely membranous, and somewhat similar male genitalia. At present the systematic position of Keirosoma is uncertain and it has been assigned to the Rhaphiinae (Foote et al., 1965), Diaphorinae (Robinson 1970a, 1970b; Pollet et al. 2004) and Sympycninae (Ulrich 1981).

Based on the cladistic analysis, I have excluded Pseudohercostomus from the Dolichopodinae; however, further analyses incorporating additional exemplars of Oriental Paraclius as well as Keirosoma are needed to elucidate the position of this genus.

Apparent autapomorphic features of Pseudohercostomus include the possession of a very wide metepimeron, the bilobate male sperm pump (Fig. 38 C) and the distinctive female terminalia with T10 densely covered with spines (Fig. 38 E,F). Stackelberg (1931) considered the 4 rows of acrostichals present in P. echinatus to be a generic character; however, I have examined a female of an apparently undescribed species from New Britain, New Guinea (CNC), which clearly possesses biserial acrostichals. This female also represents the first record of Pseudohercostomus in the Australasian and Oceanian Regions.

Material Examined. Pseudohercostomus echinatus Stackelberg, [AF, OR]: 2ɗ, 1Ψ (MNHN); 2ɗ (ISNB); Pseudohercostomus sp. 1, [AU]: 1Ψ (CNC).