[2] Millipedes in this genus are widespread in central Europe, with a distribution across about 650 km from the Harz mountains in northern Germany down to the Durmitor massif in Montenegro, and from Luxembourg and the French-Swiss border across to the Eastern Carpathian mountains in Romania.

[2] The German zoologist Karl W. Verhoeff first proposed Haasea in 1895 as a subgenus in the genus Craspedosoma to contain three species, including C.

[3] Later in same year, however, the American biologists Orator F. Cook and Guy N. Collins instead proposed Xiphogona as a genus for C. flavescens, which they designated as the type species.

[2] In 1898, the Italian zoologist Filippo Silvestri proposed Rhopalogona as a genus to replace Haasea.

Authorities have since deemed all the other names proposed for this genus to be junior synonyms of Haasea.