Hydraena discicollis Fairmaire, nomen dubium

Hydraena discicollis Fairmaire 1898b: 469 .

Through the kindness of Antoine Mantilleri I was notified that the type specimen of H. discicollis was no longer affixed to the card. The pin with the card has the following labels: "Madag Perrier; Hydraena discicollis Fm. Madag; MUSEUM PARIS MADAGASCAR PERRIER DE LA BATHIE COLL. LEON FAIRMAIRE 1906." No potential syntypes were found.

Fairmaire (1898b: 468–469) described four species of Hydraena . The original description of the first of the four ( H. dilutipes) is written in Latin. The second ( H. impressicollis) and the third ( H. borbonica) are written in French, comparing them to H. dilutipes . The fourth species described is Hydraena discicollis, and here Fairmaire returns to a Latin description, which differs markedly in wording from the description of H. dilutipes . Significantly it states that the head is "capite nigro, paulo metallico" and the prothorax is "fulvo-lutoso, disco transversim infuscato." After the Latin description, Fairmaire comments that the pronotum is "ayant de chaque cote, au milieu une forte impression arrondie."

I know of no species of Hydraena that has the combination of a black metallic head and brownish pronotum and elytra, and impressions as noted. This leads me to surmise that Fairmaire was describing a specimen of Aulacochthebius or Ochthebius, not Hydraena .

In light of the foregoing, it is necessary to treat the name Hydraena discicollis Fairmaire as a name of unknown or doubtful application, that is, a nomen dubium as per the ICZN.