PRELIMINARY STUDIES ON THE 
HYDRACARINA OF MICHIGAN: 
THE GENUS LIMNESIA, SUBGENERA 
LIMNESIOPSIS PIERSIG AND 
LIMNESIELLA DADAY^ 
By David R. Cook 
Department of Biology, Wayne University 
The genus Limnesia is represented in Michigan by mem- 
bers of four subgenera: Limnesia s.s., Tetralimnesia, Lim- 
nesiopsis and Limnesiella. Only the latter two subgenera 
will be treated in this paper. Both Limnesiopsis and Lim- 
nesiella have at times been considered to be distinct genera. 
However, most workers now look upon them as merely 
polyacetabulate members of the genus Limnesia. There 
has been some confusion between Limnesia {Limnesiopsis) 
anomala and Limnesia (Limnesiella) marshallae, the only 
previously described species belonging to these subgenera 
known from North America. It is hoped that a redescrip- 
tion of these two species will clear up this situation. In 
addition, a new Limnesiella is described from Michigan. 
Subgenus Limnesiopsis Piersig 
Limnesiopsis Piersig, 1897. Sitzungsb. Naturf. Ges. Leip- 
zig, 22/23:52. 
Subgeneric diagnosis: Genital acetabula numerous; claws 
with a series of three to five minor clawlets posterior to 
the two major clawlets; acetabular plates of male broadly 
joined at anterior and posterior ends. 
Limnesia (Limnesiopsis) anomala Koenike 
Figs. 1, 2, 7, 12 
Limnesia anomala Koenike, 1895. Abh. naturw. Ver. Bre- 
men, 13:207. 
Linmesiopsis anomala Piersig, 1897. Sitzungsb. Naturf. 
Ges. Leipzig, 22/23:52. 
Limnesiopsis anomala Marshall (in part), 1932. Trans. 
Wisconsin Acad. Sci., 27 :346. 
’Contribution from the Universit}' of Michigan Biological Station. 
146 
