DINEUTUS SENSU

SUBGENUS DINEUTUS SENSU NOV.

( FIGS 1 View Figure 1 , 7C View Figure 7 , 9E View Figure 9 , 11B View Figure 11 )

Type species: Dineutus politus Macleay, 1825 .

Synonyms: Rhombodineutus Ochs, 1926 syn. nov., Merodineutus Ochs, 1955 syn. nov.

Diagnosis: Within Dineutus , the sensu stricto subgenus can be diagnosed by the following characters: (1) head capsule of most species with a frons to clypeus ratio less than or equal to 1.5, (2) a transverse, rounded labrum, (3) distolateral angle of protibia without spine, (4) protrochanter glabrous ( Fig. 7C View Figure 7 ) – without setae apically on ventral face and (5) mesotarsal claws distinctly sexually dimorphic. The Dineutus s.s. subgenus contains the largest members of the genus (e.g. Dineutus macrochirus ) ( Brinck, 1984). Most species exhibit little to no distinguishable sexual dimorphism in terms of elytral shape. The mesotarsal claws are distinctly sexually dimorphic, but not nearly as well developed as those of the Cyclous subgenus.

Taxonomy: There are now 23 species within the sensu stricto subgenus, containing members of the former subgenera Merodineutus and Rhombodineutus . The species of this group were last treated by Mouchamps (1949b) (the original sensu stricto species), Brinck (1983) (the Rhombodineutus species) and Brinck (1984) ( Merodineutus species).

Distribution: Primarily distributed in New Guinea and Southeast Asia. One species, D. mellyi Régimbart, 1882a , extends into the far eastern Palearctic being found on the Ryukyu islands.

Discussion: The distinction of Merodineutus from Dineutus was tenuous, based primarily on elytral sculpture, protarsus and protibial modifications ( Brinck, 1984). Brinck (1984) even predicted the derivation of Merodineutus from Dineutus s.s. The subgenus Rhombodineutus was similarly based on elytral modifications resulting in a rhomboid body outline, and a more elongate labrum than other species of Dineutus ( Brinck, 1983) . Many Dineutus species show unique modifications to the elytral apices and protibial modifications as exhibited by the diversity of North American Dineutus ( Gustafson & Miller, 2015) . The large glabrous protrochanters within Dineutus are unique to this clade. For this reason, the other subgenera are synonymized with the Dineutus s.s. subgenus.

The close relation found here between Rhombodineutus and Merodineutus is novel. A phylogenetic analysis of the species of this area, including Rhomborhynchus , would prove quite interesting in elucidating directionality of colonization of New Guinea and validity of the numerous described species and subspecies ( Brinck, 1983, 1984).