Nicagus occultus Paulsen & Smith

Paulsen, M. J. & Smith, Aaron D., 2005, A new species of stag beetle from sand dunes in west Texas, and a synopsis of the genus Nicagus (Coleoptera: Lucanidae: Aesalinae: Nicagini), Zootaxa 1050, pp. 45-60 : 48-55

Nicagus occultus Paulsen & Smith , new species ( Figs. 1–2 , 3 a, 4a, 5, 7–9)

Type specimens. Male holotype, female allotype, 100 male and 20 female paratypes. Holotype and allotype deposited at FMNH, labeled: a) “ USA: TX: WARD Co. / Monahans Sandhills State / Park, N of campground on / active dunes N 31.637 W / 102.817, morning, 855 m / 5–6 JUN 2005, M.J. Paulsen”; b) “ Nicagus occultus / PAULSEN & SMITH 2005 /”, “ HOLOTYPE ” or “ALLOTYPE”. Male (63) and female (10) paratypes labeled: a) labeled as holotype; b) paratype label: “ Nicagus occultus / PAULSEN & SMITH 2005 / PARATYPE ”. Male (21) and female (4) paratypes labeled a) “ USA: TX: WARD Co. / 4 mi NE Monahans, / Monahans Sandhills SP / N 31.5731 W 102.8953 / 30 MAY 2005; AD Smith”; b) paratype label as above. Male (5) and female (4) paratypes labeled: a) “ USA: TX: Ward County / Monahans Sandhills; 4.8 mi / NE of Monahans 30.V.2005 / N 31.5731 W 102.8953, on / sand dunes, Glene Mynhardt”; b) paratype label as above. Male (3) paratypes labeled: a) “ USA: TX: WARD Co. / Monahans Sandhills State / Park, N of campground on / active dunes N 31.637 W / 102.817, pre­dusk, 855 m / 4 JUN 2005, M.J. Paulsen”; b) paratype label as above. Male (6) and female (1) paratypes labeled: a) “ USA: TX: WARD Co. / Monahans Sandhills State / Park, N of campground on / active dunes N 31.637 W / 102.817, pre­dusk, 855 m / 5 JUN 2005, M.J. Paulsen”; b) paratype label as above. Male (2) and female (1) paratypes labeled: “ USA: TX: WINKLER Co. / 8 mi. NE Kermit, N 31 56’ / 24.6” W 102 58’ 41.3”, elev. 928 m /active dunes, morning; / 6 JUN 2005; M.J. Paulsen”; b) paratype label as above. Paratypes deposited in the FMNH, CMNC, FSCA, USNM, UNSM and in the collections of J.C. Abbott (Austin, TX), L. Bartolozzi (Firenze, Italy), D.C. Hawks (Riverside, CA), S. Kawai (Tokyo, Japan), E.G. Riley & Texas A&M University (College Station, TX), P.E. Skelley (Gainesville, FL), and the authors.

Male holotype description. Length: 7.8 mm. Width: 3.5 mm. Color: Head, pronotum, legs dark brown; elytra, tarsi, antennae slightly lighter, reddish brown. Head: Eye large, entire. Anteocular margin with rounded process protruding in front of eye. Vertex tumid, in lateral view appearing subtuberculate. Frons weakly depressed behind anterior margin, margin rounded apically and produced near antennal insertions, not strongly reflexed. Clypeus (inter­mandibular projection) nearly vertical, one­third as long as broad, emarginate anteroventrally to receive labrum. Labrum semi­circular, projecting anteroventrally. Mandibles short, broad, densely setose internally, not obscured by setae, acute apically, apices prominent in dorsal view. Antennae not geniculate; scape short, not longer than combined length of segments 2–7; club closeable, elongate lamellae fitting together loosely when closed, lamellae distinctly longer than last segment of maxillary palpus ( Fig. 2 a). Surface setose, densely punctate; punctures large, contiguous. Pronotum: Lateral margins not explanate, weakly crenulate, subangulate behind middle, nearly straight from anterior margin to angulation, emarginate from angulation to acute posterior angle. Margins fimbriate with setae longer than scutellum. Surface densely punctate except at midline; punctures large, each bearing 1 long, fine seta; setae palecolored (almost colorless), erect ( Fig. 3 a). Scutellum: Surface medially and apically glabrous, punctate and setose basally. Elytra: Lateral margins crenulate, fimbriate; setae longest at base, basal setae subequal in length to scutellum. Surface punctate; punctures large, each bearing 1 long, fine seta at anterior end; setae mostly more than 2 times longer than puncture diameter, pale­colored (almost colorless), erect. Legs: Protibia quadridentate 2 basal teeth small, apical 2 teeth strongly developed, acute; spur unciform, inwardly curved. Protarsus with last tarsomere subequal in length to tarsomeres 1–4 combined. Mesotibia with weak, oblique carina at basal third; spurs both longer than basal tarsomere, acute. Metatibia robust, in lateral view gradually widening towards apex ( Fig. 5 ), apex 1/3 as wide as long, oblique; posterior face expanded ( Fig. 7 ); inferior spur subequal in length to basal tarsomere, longer superior spur subequal in length to tarsomeres 1 and 2 combined, spatulate after middle, both spurs with spatulate faces coplanar with oblique apex. External tooth of metatibia reduced to weak carina. Metatarsus plus claw length as long as metatibia. Claws long, weakly curved, subequal in length to last tarsal segment. Genitalia: ( Fig. 8 ). Median lobe short, not reaching apex of parameres, apex broadly rounded (not acuminate), apical margin continuous with ventral concavity. Parameres strongly curved dorsally.

Female allotype description. Length: 7.8 mm. Width: 3.9 mm. As holotype except in the following respects: Head: Color darker, entirely dark brown except tarsi, antennae lighter reddish brown. Eye smaller than in male. Anteocular margin with subtriangular process protruding in front of eye. Vertex tumid, in lateral view appearing subtuberculate. Antennal club oval, small, lamellae subequal in length with last segment of maxillary palpus ( Fig. 2 b). Pronotum: Lateral margin weakly crenulate, crenulation lacking behind median angulation. Elytra: Surface setose, setae fine, short, most shorter than 2 puncture diameters. Legs: Protibia quadridentate, 2 basal teeth small, 2 apical teeth more strongly developed than in male; spur simple, short, acute. All claws curved, shorter than in male. Mesotibiae with 1–2 weak external teeth; spurs both longer than basal tarsomere, acute. Metatibia robust, in lateral view gradually widening towards apex, at apex nearly 1/2 as wide as long, with external oblique carina at basal third, weakly developed; spurs broader than in male, inferior spur longer than basal tarsomere, superior spur abruptly expanded at middle, broadly rounded apically, spatulate. Metatarsus shortened, length including claw shorter than metatibia. Genitalia: Sclerotized structures similar to those of N. obscurus (see Holloway 1969) except coxites with longer setae, hemisternite of ninth segment curved internally at base, and ninth pleurite approximately 2 times wider than in N. obscurus .

Variation. Males (n=100). Male paratypes differ from the holotype in the following characters: Length: 5.8–7.9 mm. Width: 2.5–3.5 mm. Color: light brown (teneral) to dark brown. Head: Anteocular process more or less strongly developed. Frons with weak to strong excavation behind anterior margin. Vertex with median elevation variably developed from simply tumid to tuberculate. Pronotum: Lateral margin rarely with crenulations reduced to absent behind middle. Legs: Anterior tibia with basal 1–2 teeth reduced or absent. Metatibia with external tooth usually absent or present as a reduced carina.

Females (n= 20). Female paratypes differ from the allotype in the following characters: Length: 6.6–9.4 mm. Width: 3.3–4.7 mm. Color: light brown (teneral) to dark brown. Head: Anteocular margin with process subtriangular to rounded. Pronotum: Lateral margins with crenulation weak to absent. Posterior angle produced, subacute to acute. Surface with glabrous impunctate spot variably enlarged along midline. Legs: Protibia tridentate or quadridentate, 1–2 basal teeth variably reduced or absent. External oblique carina at basal third variably produced, but never toothlike.

Sexual Dimorphism. Species of Nicagus show a high degree of sexual dimorphism. Females are generally larger, darker, and more oval ( Fig. 1 ). This is accentuated in N. obscurus and N. japonicus because the dorsal punctures of males are often filled with a grayish exudate or debris. This coating was not found in any male specimens of N. occultus , but males are generally still lighter in color than females. A more useful character for determining the sexes is the size of the antennal club. In females, the antennal club is small and round with segments about equal in length to the last segment of the maxillary palpus ( Fig. 2 b). Males have a much larger club with more elongate club segments, each distinctly longer than the last segment of the maxillary palpus ( Fig. 2 a). Females also have more robust metatibiae and shorter metatarsus than do males.

Diagnosis. This species is readily separated from its only North American congener ( N. obscurus ) by its dorsal vestiture, weakly crenulate lateral pronotal margins, and shape of the metatibiae. In N. occultus the dorsum of males bears mostly long, pale­colored setae ( Fig. 3 a). This differs from the short, flattened bristles of male N. obscurus ( Fig. 3 b). Although the dorsal vestiture of females of both species consists of fine, pale­colored setae, that of N. occultus females is relatively longer and more prominent. The crenulations of the lateral pronotal margins in N. occultus are poorly developed, being weak in males and virtually absent in some females. In contrast, the crenulations are stronger and always apparent in N. obscurus . Both sexes of N. occultus possess relatively short, conical metatibiae that gradually widen towards the apex ( Fig. 5 ). The metatibiae of N. obscurus are slender in males ( Fig. 6 ), and in females are abruptly expanded after the distal third. In addition, both sexes of N. occultus have more prominent, acute mandibles, and the apical protibial teeth are stronger and more acute ( Fig. 4 a–b). The median lobe of the male genitalia is rounded ( Fig. 8 ) and not acuminate as in males of N. obscurus , and the parameres are more strongly curved dorsally.

Both Nearctic species differ from N. japonicus , which has an evenly rounded lateral margin of the pronotum (not angulate as in the Nearctic species) with stronger tooth­like crenulations. In addition, N. japonicus has the anterior margin of the clypeus subtriangular and not rounded, the claws are relatively short and subequal in length to tarsomeres 3–4 together, and males have a bidentate protibial apex ( Fig. 4 c), rather than an apex with a single large tooth.

Species of Nicagus can be immediately separated from members of the Trogidae , with which they might be confused, by the presence in Nicagus of a bisetose arolium between the claws. An arolium is not present in members of the Trogidae .

Etymology. The specific epithet is derived from the Latin “ occultus ”, meaning hidden, concealed, or secret, in reference to the elusive nature of the species that has evaded discovery by entomologists for decades in an ostensibly well­studied locality. In addition, many males were observed to remain hidden under the sand with only their antennae exposed.

Distribution. ( Fig. 9 ). United States, Texas, Monahans Sandhills.

Locality Data. UNITED STATES: TEXAS: WARD (113): Monahans Sandhills State Park (4 mi NE of Monahans); WINKLER (4): 8 mi NE of Kermit.

Temporal Data. May (28), June (89).

Nicagus obscurus (LeConte) ( Figs. 3 b, 4b, 6, 9)

Nicagus obscurus ( LeConte, 1847: 86) (Ochodaeus) .

Diagnosis. This species possesses several characters intermediate between N. japonicus and N. occultus . In males, the lateral margins of the pronotum are moderately crenulate and subangulate; not as strongly angulate as in N. occultus , nor as broadly rounded as in N. japonicus . The apical protibial teeth ( Fig. 4 b) are smaller and more rounded than in N. occultus , but more strongly developed than in N. japonicus . However, the explanate lateral margins of the pronotum are more strongly developed in N. obscurus than in either of the remaining species. In male N. obscurus , the antennal club segments are relatively longer, and the dorsum bears short, flattened bristles ( Fig. 3 b). The metatibiae of N. obscurus are elongate in males ( Fig. 6 ) and straight internally (in dorsal view), and in females are abruptly expanded after the distal third (lateral view). The median lobe of the male genitalia has a small acuminate process at the apex ( Fig. 8 ) not a broadly rounded apex as in N. occultus or N. japonicus .

Distribution. Eastern North America ( Fig. 9 ).

Locality Data. 338 specimens examined (294 male, 44 female). CANADA: ONTARIO: GREATER TORONTO AREA: Toronto (CMNC, FMNH, UMMZ, USNM); LAMBTON: Grand Bend (CNC, FSCA); MANITOULIN: Billings (CNC); NIAGARA: Grimsby (MSUC); NORFOLK: Long Point (CMNC, CNC). QUEBEC: BROME­MISSISQUOI: Brome (CNC); no locality ( Katovich & Kriska 2002).

UNITED STATES: GEORGIA: CLARKE: no locality (UGCA); FULTON/ DEKALB: Atlanta (FMNH, USNM); WHITE: Helen (UGCA). ILLINOIS: no locality (FMNH, MSUC). INDIANA: HENDRICKS: Stilesville (USNM); PARKE: Shades SP (FMNH, MJPC); TIPPECANOE: Wildcat Creek (FSCA), no locality (FMNH, MJPC, MSUC, UGCA, USNM); WARREN: no locality (FMNH). IOWA: JOHNSON: Iowa City (USNM); LEE: Shimek SF (MJPC); LINN: Indian Creek Nature Center (MJPC); STORY: Ames (CMNC, FMNH). KENTUCKY: LIVINGSTON: no locality (USNM). MARYLAND: ALLEGANY: Green Ridge SF, Oldtown (CMNH); ANNE ARUNDEL: Crofton (CMNH); MONTGOMERY: Plummers Island (USNM); PRINCE GEORGE’S: Berwyn (USNM), College Park (CMNC, USNM), Laurel (CMNH), Riverdale (USNM). MASSACHUSETTS: MIDDLESEX: Lowell (CNC); no locality (FMNH). MICHIGAN: BERRIEN: Warren Dunes (FMNH); OAKLAND: no locality (MSUC, UMMZ); ST. CLAIR: Port Huron (USNM); VAN BUREN: South Haven (CUAC); WAYNE: Detroit (USNM). MINNESOTA: ST. LOUIS: Duluth (INHS). NEW HAMPSHIRE: GRAFTON: Plymouth (CNC, FMNH, FSCA, UMMZ). NEW JERSEY: ESSEX: Newark (USNM). NEW YORK: ERIE: Buffalo (INHS); ONEIDA: Sylvan Beach (CNC); OSWEGO: Selkirk Beach (FMNH, MSUC, UNSM); SUFFOLK: Montauk (FMNH, FSCA), Napeague (INHS), Riverhead (CMNC), Wading River (CMNC, FMNH, FSCA, USNM). NORTH CAROLINA: WAKE: Raleigh (CMNC). OHIO: FAIRFIELD: Barnebey Center (CMNH, FSCA), Revenge (CMNH, MJPC); HOCKING: no locality (CMNC, FSCA, UNSM); PIKE: Liberty (KDKC, RAAC), Jackson Lake (CMNH); RICHLAND: Shelby (RAAC); VINTON: Lake Hope SP (CMNH, MLJC). SOUTH CAROLINA: OCONEE: Salem (CUAC); PICKENS: Clemson (FMNH, USNM); SPARTANBURG: Spartanburg (CUAC). PENNSYLVANIA: ALLEGHENY: Guyasuta Run (CMNH), no locality (USNM); LYCOMING: Loyalsock Creek (CMNH); NORTHUMBERLAND: Milton, Milton SP (CMNH); WESTMORELAND: Jeannette (CMNH). VIRGINIA: FAIRFAX: Black Pond, Dead Run, Great Falls (USNM), Springfield (CMNH). WASHINGTON, D.C.: Rock Creek (USNM). WISCONSIN: BAYFIELD, no locality (USNM), Quarry Point ( Katovich & Kriska 2002); DOUGLAS: Brule Point ( Katovich & Kriska 2002).

Figures

FIGURE 1. Dorsal habitus of N. occultus: a) male and b) female.

FIGURE 2. Head and right antenna of N. occultus (ventral view) of: a) male and b) female.

FIGURE 3. Vestiture of pronotum (lateral view) in male a) N. occultus and b) N. obscurus.

FIGURE 4. Protibial dentation (dorsal view) of male: a) N. occultus, b) N. obscurus, and c) N. japonicus.

FIGURE 9. Distribution of Nearctic species of Nicagus, indicated by triangles (N. occultus), or circles (N. obscurus). An open circle indicates a state record without specific locality data.

FIGURES 5 – 8. 5. Lateral view of male N. occultus, illustrating diagnostic characters: short, conical metatibia; weakly curved claws; and dorsally curved parameres. 6. Lateral view of elongate male metatibia of N. obscurus. 7. Apex of metatibiae of male N. occultus. 8. Male genitalia of N. occultus (dorsal view), showing rounded apex of median lobe.