Dineutus amazonicus Hatch, 1930

Gustafson, Grey T. & Miller, Kelly B., 2015, The New World whirligig beetles of the genus Dineutus Macleay, 1825 (Coleoptera, Gyrinidae, Gyrininae, Dineutini), ZooKeys 476, pp. 1-135 : 20-21

Dineutus amazonicus Hatch, 1930

Dineutus (Cyclinus) amazonicus Hatch, 1930: 16.

Type locality.

U.S.A., Arkansas, "Sevier Co., Ark. Saline R. about 18 miles east of DeQueen."

Material examined.

None-see comments below in Discussion.

Diagnosis.

Male: unknown.

Female: Length 10 mm, elytral apices regularly oval, serration absent, lateral margins weakly sinuate, profemora of female with apicoventral tooth present running 1/5 its length.

Distribution.

Known only from the type locality.

Habitat.

Unknown

Discussion.

Dineutus amazonicus was described from a single female specimen collected in Arkansas during the 1930's. The species, as described by Hatch (1930), is unique among all other North American Dineutus in having females with an sub-apicoventral tooth present on the profemora, running approximately 1/5 its length. In Dineutus this is a commonly sexually dimorphic character, with the tooth present only in males. Hatch (1930) indicated the elytra of this species are similar to those of Dineutus emarginatus , being regularly rounded and lacking serration.

We were unable to locate the type specimen either at the Smithsonian (F. Shockley, pers. comm.) or Oregon State University (C. Marshall, pers. comm.) where Hatch’s collection was deposited. No specimens in the University of Arkansas collection were identified as Dineutus amazonicus (J. Barnes, pers. comm.). It appears that the type may be missing, and that no other published records of this species have occurred since its description in 1930. Although Hatch’s (1930) description at first sounds dubious, as the profemoral sub-apicoventral tooth is in all other species unique to males, Hatch was unlikely to mistake a female gyrinid for a male ( Hatch 1925b, 1926), and it therefore seems unlikely that he described a merely aberrant form. For this reason we have included the enigmatic Dineutus amazonicus , without having seen neither type nor any other specimens of this species.

The first author recently visited the type locality in an attempt to recollect this species, but was unsuccessful. The locality, Saline River, a large mud bottom river, also had present Dineutus ciliatus as described by Hatch (1930), but unsettlingly, the only other species collected at this locality was Dineutus emarginatus , the species stated to be most similar to that of Dineutus amazonicus . Hopefully in the future the type may be rediscovered or this enigmatic species recollected and its relationship with Dineutus emarginatus clarified.