Dineutus, W. S. Macleay, 1825

Gustafson, Grey T., Hájek, Jiří & Miller, Kelly B., 2016, Description of two new species of Dineutus sensu stricto from Southeast Asia (Coleoptera: Gyrinidae) with a key to the known species of the subgenus, Acta Entomologica Musei Nationalis Pragae 56 (2), pp. 629-643 : 631-633

Subgenus Dineutus sensu stricto W. S. Macleay, 1825

The Dineutus s. str. species share the following features: generally large (normally at least 14 mm in length, up to 20 mm); coloration dorsally olive greenish, ventrally dark reddish brown; elytra typically with a narrow region of effaced reticulation in scutellar and sutural regions, apices regularly rounded with at least some form of apicolateral sinuation; protrochanters smooth and unmodified, without setae distally on ventral surface; profemora of male with two sub-apicoventral teeth; female ultimate protarsomere posteriorly with setose furrow; male mesotarsal claws similar among species, ventral margin strongly curved, narrowed in apical third.

Species of the subgenus exhibits very little sexual dimorphism (unlike the North American species assigned to subgenus Cyclinus Kirby, 1837 , or some African species of the subgenus Protodineutus Ochs, 1926 ( BRINCK 1955, GUSTAFSON & MILLER 2015)). The only known sexual dimorphism, in addition to obligate enlarged male protarsomeres with adhesive setae, is general size with males larger than females and often with the elytra slightly laterally expanded near midlength, giving them a somewhat more attenuated appearance anteriorly. There is no conspicuous sexual dimorphism in the shape of the elytral apices.

The species are found from southwestern China, through most of eastern China south of Beijing to Taiwan and the Ryukyu Islands, south through southeast Asia and the lesser Sunda Islands as far east as Timor.