[4] Although listed as extinct by the IUCN, the limited studies conducted on water beetles in Brazil means that it might still survive.

[3] The first specimen of B. ducalis was collected in the 19th century from an unknown locality in Brazil and is kept at the Natural History Museum, London.

[2] In 2019, a study reported 10 additional specimens (including the first female of the species), all collected in the late 19th century, discovered incidentally in the National Museum of Natural History of France.

While the original holotype lacked any exact location data, the new specimens all indicate that they were collected in Santo Antonio da Barra (now known as Condeuba) in the southern part of Bahia, Brazil.

[1] Considering the absence of information about the species and the limited studies conducted on water beetles in Brazil, it might still survive.