Hydrophilus ater Olivier Hydrophilus ensifer is a species of water scavenger beetle in the family Hydrophilidae found in the Americas.

[1] As of 2020, there are two valid subspecies of H. ensifer, H. e. ensifer and H. e. duvali,[2] however the differences among the subspecies are not well understood.

[3] The genus Hydrophilus are among the largest aquatic insects.

[4][5] Hydrophilus ensifer is found from Argentina northwards throughout most of South America, through Central America north into central Mexico, and throughout the Caribbean.

[5][4] Hydrophilus ensifer reaches as far north as South Florida in the United States.