''Megadytes ducalis'' is a

species In biology, a species is the basic unit of Taxonomy (biology), classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of ...

water beetle A water beetle is a generalized name for any beetle that is adapted to living in water at any point in its life cycle. Most water beetles can only live in fresh water, with a few marine species that live in the intertidal zone or littoral zone. T ...

in the family

Dytiscidae The Dytiscidae – based on the Greek ''dytikos'' (δυτικός), "able to dive" – are the predaceous diving beetles, a family of water beetles. They occur in virtually any freshwater habitat around the world, but a few species live ...

. With a length of , it is the largest species in the family. Until recently, the species was only known from a single

specimen Specimen may refer to: Science and technology * Sample (material), a limited quantity of something which is intended to be similar to and represent a larger amount * Biological specimen or biospecimen, an organic specimen held by a biorepository ...

that was collected in the 1800s from

Brazil Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...

, but more specimens were discovered in 2019.

History

The first specimen of ''M. ducalis'' was collected in the 1800s from an unknown locality in Brazil. Rumors indicate it was found in the bottom of a canoe in the

Amazon Amazon most often refers to: * Amazons, a tribe of female warriors in Greek mythology * Amazon rainforest, a rainforest covering most of the Amazon basin * Amazon River, in South America * Amazon (company), an American multinational technolog ...

. In 2019, a study reported 10 additional specimens (including the first female of the species), all collected from the end of the 19th century, discovered incidentally in various historical collections. While the original holotype lacked any 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. Villagers in the region were involved in insect trade, capturing the much sought after specimens of ''

Hypocephalus armatus ''Hypocephalus armatus'', the mole beetle, is a species of beetle in the family Vesperidae. It is the only species in the genus ''Hypocephalus''. Both the genus and species were first described by Anselme Gaëtan Desmarest in 1832. It is found i ...

'' found around the region. As a consequence of the lack of recent records, the IUCN lists it as extinct. Considering the absence of information about the species and the limited studies conducted on water beetles in Brazil, it might still survive.

Morphology

''Megadytes ducalis'' is a large and robust beetle with total length ranging from 42.9 to 47.7 mm. It is distinctly larger than congeners such as '' M. lherminieri'' and ''M. magnus'', and not as broadly oval in shape as them. The two sexes of ''M. ducalis'' are externally similar, except for females being shiny without any signs of striae on the dorsal surface, and lacking protarsal disks and yellow setae on ventral surface of mesotarsomere I.

Ecology

Dytiscidae in general are aquatic and are predators as both adults and larvae.

Distribution

This species appears to have a restricted distribution in the

cerrado The ''Cerrado'' (, ) is a vast ecoregion of tropical savanna in eastern Brazil, particularly in the states of Goiás, Mato Grosso do Sul, Mato Grosso, Tocantins, Minas Gerais, and the Federal District. The core areas of the Cerrado biome are ...

of Western Brazil.

References

Dytiscidae Extinct animals of Brazil Beetles described in 1882 Taxonomy articles created by Polbot Extinct insects {{Dytiscidae-stub