1963] 
Young — Hydrovatus 
191 
ously broad and flat; the 7th and 8th broader and flatter than usual; 
the nth modified, laterally excised. Coloration: Head and pronotum 
brownish yellow, pronotum somewhat darker on disk than at sides; 
elytra dark brown, lighter on lateral margins particularly toward 
apices, but without indication of any maculation. Venter and append- 
ages nearly uniformly brownish yellow. Male Genitalia (fig. 8) : 
Parameres of general type of pustulatus; tips less rounded than in 
concolor (fig. 7). Aedeagus flexulose at tip, finer and less abruptly 
narrowed than in concolor. 
Allotype female: Similar to male except for unmodified antennae; 
sex doubtfully determinable by the narrower anterior and middle 
tarsi. Microsculpture and punctation very similar. Coloration 
throughout slightly darker than holotype. Total length, 2.40 mm; 
greatest width, 1.80 mm; width at base of pronotum, 1.55 mm; 
width at apex of pronotum, 1.02 mm; length of pronotum at midline, 
0.69 mm ; length from base of prosternal process to tip of coxal lamina, 
1. 10 mm; width between eyes, 0.69 mm. 
Variation : The series before me varies slightly in color some speci- 
mens being darker and presumably more fully hardened than others. 
A series from Lanier County, Georgia, are particularly darker below 
than those from central Florida. 
Type locality: Holotype and allotype: FLORIDA: Alachua Coun- 
ty, Payne Prairie south of Gainesville, vii.23.1960, F. N. Young (in 
UMMZ). Paratypes, to be distributed to other museums: 8, same 
data as types; 27, same locality, viii.21-22, 1961. Alachua Co., San 
Felasco Hammock west of Gainesville, 2, x.5.1948; 1, ix.13.1950. 
Alachua Co., Lake Newnan east of Gainesville, 1, ix.27.1939. Gads- 
den Co., Chattahoochee, 2, vi. 13. 1954. Jackson Co., Cypress pond 
east of Marianna, 2, vi. 14. 1954. GEORGIA: Lanier Co., Pond 
south of Raysville, 15, vii.13.1960. All collected by F. N. Young. 
The two species described above will run in my key (Young 1956) 
to couplet four but are immediately distinguishable from davidis J. 
Balfour-Browne by size, body form, elytral punctation, and genitalia 
and from pustulatus by the genitalia and characters given under the 
diagnoses. 
I wish to express my thanks to Mr. J. Balfour-Browne and other 
members of the staff of the British Museum (Natural History) for 
their assistance and tolerance during my studies of the types of Ameri- 
can aquatic beetles in that institution. 
