F. N. Young.
Two New North American Species of Hydrovatus, with Notes on Other Species (Coleoptera: Dytiscidae).
Psyche 70(3):184-192, 1963.

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TWO NEW NORTH AMERICAN SPECIES OF
HYDROVATUS, WITH NOTES ON OTHER SPECIES
(COLEOPTERA : DYTISCIDAE)
BY FRANK N. YOUNG
Department of Zoology, University of Indiana The North American species of Hydrovatus 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 Hydrovatus. 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. 19. 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 pustulatus Melsheimer (fig. 10) , new combination to replace I$. cuspidatus pustulatus Melsh. (Young, 1956) and H. pustulatus co7npresxus Sharp (fig. g), new combination to replace 13. cuspidatus conzpressus Sharp (Young, 1956). 'Contribution No.
729 from the Zoological Laboratories of Indiana Uni- versity, aided by grants from the TJ. S. Public Health Service and the National Science Foundation.
Manuscript received by the editor December 26, 1962.



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The relationship between pustulatus and compresyus is still not completely determined, but the two apparently represent the extremes of a single species which varies geographically. Typical pustulatus decreases in size from north to south and possibly also to the east in North and South Carolina and Georgia. The largest specimens I have seen are from Wisconsin, Michigan, New York, Illinois, and Indiana. Specimens from Virginia, Tennessee, Arkansas, and northern Louisiana are smaller although very similar in other respects. Speci- mens from Cherokee County, Alabama; Mitchell, Lanier, Baker, and Decatur counties, Georgia; Houston County, Alabama; and Calhoun, Jackson, and Walton counties, Florida, apparently represent inter- grades between typical pustulatus and the smaller, darker compressus. The latter apparently replaces pustulatus in the Atlantic and Gulf Coastal plain from Louisiana to North Carolina, although occasional specimens occur which have when teneral elytral markings of the type of pustulatus.
The male genitalia (fig. 3)
of the single type of compressus (in
BMNH) is as far as I can see identical with those of pustulatus (fig. 2) and with those of numerous specimens examined from throughout the range. Specimens from southern Florida tend to be smaller and somewhat more coarsely punctate than the type of com- pressus, but in other respects agree with it perfectly. Specimens from North Carolina (Brunswick Co., Near Bishop, vii.25.1959, F.N. Young in University of Michigan Museum of Zoology) and South Carolina (Beaufort Co., Cambahee River marsh, vii.25.1959, F.N. Young in UMMZ) although variable are also very similar to the type of comfiressus. I have also seen a single female from the Bahamas (San Salvador Island, near Cockburn Town, iii.18.1953, E. B. Hayden in American Museum of Natural History) which probably also repre- sents conipressus.
Hydrovatus inexpectatus new species
DIAGNOSIS: A small, pale Hydrovatus (fig. 4) similar in shape to the Brazilian crassulus Sharp (fig. 6), but differing from that species in the smaller size (1.89-2.15 mm in length) and the different structure of the clypeus. Body form less convex than any of the American species and with the sides of the elytra converging so gradually that they appear almost parallel-sided when viewed from above. Male 'The genitalia of the type were unfortunately lost after the above figures were drawn. A specimen from Florida with genitalia intact and previously compared with those of the type has been deposited in the BMNH.



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186 Psyche [September
aedeagus unique (fig. 5) among the American species (male of crassulus unknown to me), the broadened tip suggesting some of the Old World species.
HOLOTYPE MALE: Body form irregularly elongate oval, the sides of the elytra when viewed from above less strongly arched than in most species and thus giving the appearance of being parallel-sided in the middle portion, gently converging posteriorly until the sides curve sharply in and then recurve to form the acuminate tip; in profile, body arched dorsally but somewhat flattened on pronotum ; ventral profile less arched than usual, almost flat. Total length, 1.98 mm; greatest width, I .2g mm ; width at base of pronotum, I .20 mm ; width at apex of pronotum, 0.82 mm; length of pronotum at midline, 0.43 mm; length from base of prosternal process to apex of coxal lamina, 0.86 mm; width between eyes, 0.52 mm. Head distinctly microreticulate, the meshes impressed so that surface is only feebly shiny; meshes finer on clypeus than on front and vertex; punctation fine, sparse, and ir- regularly distributed ; clypeus with distinct margin, the margin irregu- lar and somewhat thickened at middle but not noticeably truncate and not sharply raised in middle (not as described for c? of cramlus, Zimmermann I 92 I : 191 ) ; antennal tubercles, feeble clypeal tubercles, and punctate clypeo-frontal grooves much as in pustulatus and other species, but clypeal tubercles somewhat more distinct; usual rows of punctures near eyes difficult to see because of the impressed micro- sculpture; arms of tentorium (?) vaguely visible through the thin integument running from antennal bases to converge on the front. Pronotum with impressed microreticulations much as on vertex of head ; usual transverse anterior row of punctures and discal punctures coarser than punctures on head, the latter somewhat irregularly dis- tributed but denser than on head; sides distinctly margined, the mar- gins nearly straight with anterior angle acute; angle of pronotal margin with elytra when viewed from the side very obtuse. Elytra with impressed microreticulation as on head and pronotum but the meshes coarser and more regularly hexagonal ; punctation coarse, deep, rather regularly distributed ; punctures coarser than on pronotum, separated by from two to four times the diameter of a single puncture; inter- mediate series of punctures indistinguishable from others ; elytral margins distinct, curved in profile, not visible from directly above; no distinct sulci on sides of elytra; tip moderately acute, somewhat deflexed. Venter: Prosternal process broadly triangular, the tip cephalad forming a minute ventral hook; disk of process microreticu- late, the lateral (hind) angles irregularly minutely tuberculate ; lateral



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19631 Young - Hydrovatus 187
borders indistinct. Hind coxae coarsely microreticulate and with large punctures separated by from one to two times the diameter of a single puncture. Abdominal sternites microreticulate, the meshes irregular and not deeply impressed; first visible sternite coarsely but shallowly and irregularly punctate; fused 2nd and 3rd sternites with a few coarse but shallow and scattered punctures on 2nd ; last visible sternite pointed behind, the point deflexed. Anterior and middle tarsi mod- erately expanded ; middle tibiae with a few large setigerous punctures on anterior face; antennae not evidently modified, not noticeably thicker than in female. Coloration: Head and pronotum light red- dish yellow. Elytra darker, light reddish brown except along suture and sub-basal and postmedian fascia or spots which are lighter (lighter markings more evident in other specimens in series.) Venter light reddish yellow including legs and
antennae. Male genitalia with
parameres of usual type for American species but aedeagus distinctive (fig. 5) in lateral aspect acuminate to tip and feebly recurved; in ventral aspect broadened toward tip and spatulate. ALLOTYPE FEMALE: Very similar to holotype; sex apparently deter- minable only by dissection. Cl~peus not detectably different from that of male except that the clypeal tubercles are reduced. Microsculp- ture and punctation very similar to holotype. Color somewhat lighter on all parts. Total length I .g8 mm; greatest width, I 20 mm ; width at base of pronotum, 1.02 mm; width at apex of pronotum, 0.82 mm ; length of pronotum at midline, 0.43 mm; length from base of pros- ternal process to apex of coxal lamina, 0.86 mm; width between eyes, 0.52 mm.
VARIATION : The paratype series varies somewhat in color - some specimens being slightly darker, particularly on the elytra, and some have light markings more distinct. The types may be slightly teneral. TYPE LOCALITY : Holotype and allotype : FLORIDA : Alachua Coun- ty, Payne Prairie south of Gainesville, vii.23.1960, I?. N. Young (in UMMZ).
Paratypes: I d same data (U. S. National Museum) ; i c? same data (Museum of Comparative Zoology) ; I ? same locality, viii.21.1961 (California Academy of Science ) ; I 9 same locality, viii. 21.1961 (BMNH) ; I $ same locality, viii.22.1961 (American Mu- seum of Natural History) ; 2 $ FLORIDA: Dade County, Miami, ix. I 3. I 960, blacklight trap, P. E. Briggs (Florida State Collection) . Hydrovatus ~latycornis new species
DIAGNOSIS: A medium sized, dark colored, and immaculate Hydro- vatus (fig. I 2) similar to the Mexican concolor Sharp (fig. I 3) but



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I 88 Psyche [September
differing from all the known American species in the flattened and widened intermediate antennal segments in the male (fig. I I). Larger and less attenuate behind than pustulatus com~ressus Sharp with which it has usually been found associated; smaller, more attenuate behind, and more finely punctate than peninsularis Young with which it was also associated. Male genitalia of same general type as in pustzdatus but differing in shape of aedeagus and parameres. Al- though the antennal n~odification suggests some of the African species, the genitalia and other characters indicate relationship with the Ameri- can group.
HOLOTYPE MALE: Body form broadly oval, less strongly attenuate behind than concolor; broadest at about basal third of elytra; dorsal profile convex, regularly curved; ventral profile not strongly arched; (Scale: 1 mm
approximately 10 mm on figure at X 10;
approximately 34 mm at X 40; approximately 46 mm at X 60.) 1. Hydrovatus cuspidatus Kunz., Corsica: Bastia, E. Reveliere (Sharp coll., BMNH). L-R. Ventral view of male aedeagus X 60; lateral view aedeagus X 60; inner face left paramere X 60; outer face right para- mere X 60.
2. H. pustulatus pustulatus Melsh. Indiana : Monroe Co., Bloomington, x.20.1952, J. R. Munsee (UMMZ).
L-R. Ventral view of male aedeagus
X 60; lateral view of aedeagus X 40; outer face right paramere X 40. 3. H. pustulatus compressus Sharp. Louisiana: New Orleans (male type in BMNH). Same as 2
4. H. inexpcctatus new species. Dorsal outline of holotype (UMMZ) X 10. 5. H. incxpectatus new species. Holotype (UMMZ). As in 2 and 3. 6. H. crassulus Sharp. Brazil. Dorsal outline of female cotype (BMNH) X 10.
7. H. concolor Sharp. Mexico: Mexico City, Hoge. Male cotype (BMNH). L-R. Ventral view of aedeagus X 60; prosternal process X 40; lateral view of aedeagus X 60.
8. H. platycornis new species. Holotype male (UMMZ). L-R. Ventral view of aedeagus X 60; prosternal process X 40; lateral view of aedeagus X 60; right paramere X 60.
9.
H. pustulatus compressus Sharp.
Dorsal outline of male type (BMNH)
X 10.
10.
H. pustulatus pustulatus Melsh.
Dorsal outline of male (same as fig. 2)
X 10.
11. H. platycornis new species. Right antenna of holotype X 60. 12. H. platycornis new species. Dorsal outline of holotype X 10. 13. H. concolor Sharp. Same data as fig. 7. Holotype male (BMNH) X 10. Note: The male genitalia of Dytiscidae are retracted into the body on the side. In copulation they are extruded outward, rotated, and projected forward and downward. The parts in the above figures are designated in relation to the copulatory position. Dashed or cross-barred areas are easily distorted membranous portions or portions broken in dissection. The dashed line across the parameres represents the base of the sheath into which the genitalia are withdrawn into the body.




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190 Psyche [September
more strongly convex in dorsal profile, less strongly convex in ventral profile than peninsularis, much as in pustulatus. Total length, 2.49 mm ; greatest width, I .SO mm ; width at base of pronotum, I .60 mm ; width at apex of pronotum, I .02 mm; length from base of prosternal process to apex of coxal lamina, 1.10 mm; width between eyes, 0.69 mm. Head microreticulate much as described in inexpectatus but meshes somewhat less impressed, the surface appearing more shiny; clypeal tubercles reduced; clypeo-frontal grooves more closely and heavily punctate; punctures along inner margins of eye difficult to see, apparently not setigerous; clypeal margin distinct, feebly truncate at middle, and bordered behind by an indefinite groove; punctation fine, sparse, and irregularly distributed. Pronoturn microreticulation coarser and more deeply impressed than on head but surface mod- erately shiny; punctation on disk coarse and dense compared with that on head, rather uniformly distributed but irregularly spaced; anterior row of coarse punctures not readily distinguished from discal punctation; punctation finer toward margins; sides distinctly mar- gined, gently curved, anterior angles moderately acute; angle of pro- notal margin with elytral obtuse but less so than in inexpectatus, about as in pustulatus. Elytra microreticulate about as on pronotum, meshes not deeply impressed, the surface moderately shiny; punctures coarser than on pronotum, more regular in size, and having a tendency to form irregular rows although not nearly as coarse nor with intermediate series of punctures forming such distinct rows as in concolor; humeri moderate, a feeble, punctate groove behind them above a feeble ridge; both groove and ridge more evidnt than in pustulatus but much less evident than in concolor. Venter: Prosternal process triangular with anterior end truncate ; distinctly but narrowly margined at sides ; disk punctate with inconspicuous microreticulations. Hind coxae and coxal lamina with very coarse, dense punctation, the punctures separated by less than the diameter of a single puncture and sometimes confluent; interspaces with irregular rugose sculpture but moderately shiny. First visible abdominal sternite and 2nd (fused with 3rd) with coarse punctures much as on coxae; interspaces with rugose sculpture repre- senting the coarse, deeply impressed meshes of the microreticulation evident on other abdominal sternites; meshes of abdominal microretic- ulation elongate ; last visible sternite acuminate behind, the tip deflexed. Anterior and middle tarsi moderately expanded, slightly more so than in female. Middle tibiae rather coarsely and densely punctate on anterior face, the punctures setigerous and irregular in shape. Antennae (fig. I I) with 3rd through 6th segments conspicu-



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19631 Young - Hydrovatus 191
ously broad and flat; the 7th and 8th broader and flatter than usual; the I ith modified, laterally excised. Coloration: Head and pronoturn 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, I .80 mm; width at base of pronotum, 1.55 mm; width at apex of pronotum, I .02 mm ; length of pronoturn at midline, 0.69 mm; length from base of prosternal process to tip of coxal lamina, 1.10 mm; width between eyes, 0.69 mrn.
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, I?. 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. I 948 ; I, ix. I 3. I 950. Alachua Co., Lake Newnan east of Gainesville, I, ix.27.1939. Gads- den Co., Chattahoochee, 2, vi.13.1954. Jackson Co., Cypress pond east of Marianna, 2, vi.14.1~54. 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.



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Psyche
[September
YOUNG, F. N.
1956.
A preliminary key to the species of Hydrovatus of the Eastern United States (Coleoptera: Dytiscidae). Coleopt. Bull. 10 : 53-54. ZIMMERMANN A.
1921. Beitrage zur Kenntnis der siidamerikanischen Schwimmkaferfauna nebst 41 Neubeschreibungen. Archiv fur Naturgesch, 87 (Abt. A. Heft 3) : 181-206.




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