1954] 
Cook — Hydracarina of Michigan 
147 
Male: Length of body 1.3-1. 5 mm; length of genital field 
0.43-0.46 mm; width of genital field 0.49-0.54 mm. 
Body rounded, integument soft; a pair of small sclerites 
present near posterior end of dorsum, these plates approxi- 
mately 0.07 mm in length; acetabular plates broadly joined 
at both ends, length of genital opening less than one-half 
length of genital field; genital acetabula numerous (55-65 
on each side), two pairs of acetabula considerably larger 
than the others; apodemes of posterior border of third 
coxae complete. 
Palps large and powerful; the dorsal lengths of the pal- 
pal segments, in millimeters, varied as follows : P-I, 0.031- 
0.040 mm; P-II, 0.224-0.240 mm; P-III, 0.184-0.204 mm; 
P-IV, 0.392-0.406 mm; P-V, 0.092-0.095 mm; peg on ven- 
tral side of P-II located on a slightly raised tubercle, peg 
projecting directly outwards (Fig. 7) ; swimming hairs 
present on third and fourth pairs of legs ; claws with minor 
clawlets present posterior to the major clawlets. 
Female: Length of body 1.4-1. 6 mm; length of genital 
field 0.35-0.37 mm; width of genital field 0.33-0.38 mm; 
width of pregenital sclerite 0.21-0.23 mm. 
Body, legs and palps similar to those of male except 
that they average slightly larger; 58-67 genital acetabula 
on each side; acetabular plates not united as in male, but 
able to open and close over the genital valves; posterior 
portion of genital field only slightly wider than anterior 
portion. 
Habitat: Most commonly taken in lakes but the author 
has one record from a permanent pond. Although this 
species is an excellent swimmer, it is often found crawl- 
ing about in cracks and crevices of submerged logs. 
Range: Marshall (1932) lists this species from New 
York, Wisconsin and Michigan. Limnesia {Limnesiopsis) 
anomala has been taken in only eleven Michigan counties. 
However, these are widely scattered and it is likely that 
this species occurs throughout the state. 
Subgenus Limnesiella Daday 
Limnesiella Daday, 1905. Zoologica, 44 :306. 
Neolimnesia Lundblad, 1936. Zool. Anz., 116:202. 
Subgeneric diagnosis : Genital acetabula numerous ; claws 
