Excerpt: Members of the water mite genus Hydrochoreutes have a Holarctic distribution. They are found in lakes, ponds, and sluggish streams, but usually only in small numbers and therefore long series of specimens are difficult to obtain. Two species, ungulatus (Koch) and krameri Piersig, have a widespread range in Europe and Siberia and the latter species is also known from Algeria. Marshall (1937) reported ungulatus from Maine, Michigan, Wisconsin and California. However, the present author has seen no specimens from North America which can be assigned to the latter species and the illustrations in Marshall's paper are definitely not those of ungulatus. Therefore. there are no authentic records of the latter species in the New World. Cook (1956) named a new species, intermedius, from North America. Both the description and illustrations are inadequate for the latter and it is treated along with four new species in this paper.
Cook, David R.
"North American Species of the Genus Hydrochoreutes (Acarina: Pionidae),"
The Great Lakes Entomologist, vol 3
Available at: https://scholar.valpo.edu/tgle/vol3/iss4/3