TWO NEW NORTH AMERICAN SPECIES OF 
HYDROVATUS , WITH NOTES ON OTHER SPECIES 
(COLEOPTERA: DYTISCIDAE) 1 
By Frank N. Young 
Department of Zoology, University of Indiana 
The North American species of Hydrovcitus still present some of 
the most perplexing problems found among the water beetles. The 
western United States and Mexican species are particularly poorly 
known, and considerable work is needed before a satisfactory tax- 
onomic treatment of the Nearctic fauna can be completed. Even in 
the eastern United States, several problems remain and new species 
may be found as characteristics for their separation are discovered. 
The two new species described below were first recognized in mass 
collections from Payne Prairie south of Gainesville, Florida. Once 
their distinctiveness was realized other specimens were found either 
mixed with other species in the collection or in unsorted material. 
The series from Payne Prairie were sorted out from among approxi- 
mately 5,000 specimens of other species of Hydrovcitus. 
After examining and dissecting specimens of the Palearctic H. 
cuspidatus Kunze in the British Museum (Natural History), I am 
convinced that I was completely in error in referring the Nearctic 
pustulatus Melsheimer and compressus Sharp to this species. H. cus- 
pidatus and clypealis Sharp, although superficially similar to pustula- 
tus differ in several important respects. Both, for example, have a 
ridge with cross striations on the anterior border of the hind coxae 
which probably functions as a stridulatory organ, and in both species 
the male genitalia are of an entirely different type from any of the 
American species. The parameres are complex, in cuspidatus (fig. i) 
there is a distinct hook at the apex and in clypealis chitinous pieces 
curve in at the tip and membranous lobes project irregularly. The 
shape of the aedeagus is distinctive in both species. 
In consequence, the American forms need to be reassigned as fol- 
lows: Hydrovatus pustulatus puslulatus Melsheimer (fig. io), new 
combination to replace H. cuspidatus pustulatus Melsh. (Young, 
1956) and H. pustulatus compressus Sharp (fig. 9), new combination 
to replace H. cuspidatus compressus Sharp (Young, 1956). 
Contribution No. 729 from the Zoological Laboratories of Indiana Uni- 
versity, aided by grants from the U. S. Public Health Service and the National 
Science Foundation. 
Manuscript received by the editor December 26, 1962. 
184 
