Bolborhinum Boucomont, 1911

Mondaca, José & Smith, Andrew B. T., 2008, A revision of the southern South American genus Bolborhinum Boucomont (Coleoptera: Geotrupidae: Bolboceratinae), Zootaxa 1794, pp. 1-48 : 5-10

Genus Bolborhinum Boucomont, 1911

( Figs. 1–37 , 47, 50, 53)

Bolborhinum Boucomont, 1911: 339 (as a subgenus of Bolboceras ). Type species: Bolboceras tubericeps Fairmaire, 1861 by original designation. Gender: neuter.

Description. Form ( Figs. 1–37 ): Color usually reddish-brown to black, the lighter brown coloration of some specimens is likely the incomplete sclerotization of newly emerged adults (teneral coloration); body spherical, strongly convex. Size moderate (length 7.5–22.0 mm; width 4.0–10.0 mm). Head in male: Subtriangular or trapezoidal, longer than wide. Mandible with outer margin rounded, weakly sinuate or almost straight, anteriorly with apex acute, curved inwards. Labrum with apex variably emarginated; dorsal surface rugose or rugopunctate. Clypeus and frons with variable ornamentation ( Figs. 1–37 ). Some species have cephalic armature that is either comprised of 1 horn at midline of clypeal apex or of 2 horns. In the case of 2 cephalic horns, 1 is at the midline of clypeal apex and the other horn (depending on the species) is either located on the clypeus immediately behind the first or further back at the frontoclypeal margin or between the eyes. Another type of armature consists of a large anteriorly directed clypeal horn and 2 large horns that originate in the ocular margin. In some cases, the cephalic armature either consists of 1 anteriorly directed clypeal horn and 4–5 small horns situated behind the clypeal horn in different places on the head or with a prominent trapezoidal frontal tubercle formed by 4 tubercles joined laterally by a longitudinal carina. Frons impunctate to sparsely punctate, finely rugose. Vertex dorsally smooth, only with micropunctures, flat or depressed. Antenna with 11 antennomeres; antennomere 1 shorter than 2–8 combined. Antennal club ovoid, with 3 antennomeres ( Fig. 47); outer antennomere usually more convex than the inner antennomere; dorsal surface completely setose; basal antennomere weakly convex, often nearly flat; dorsal surface partially setose on outer distal margin. Eyes partially divided by canthus; eye canthus with outer lateral margin arcuate or straight, surface generally rugopunctate. Pronotum: Sexually dimorphic, males generally with deeper anteromedian excavations. Pronotum transverse, convex, without horns, generally with deep and wide anteromedian excavation (except in B. tricorne ); dorsally either with posterior transverse ridge parallel to basal margin (not always present in Bolborhinum ) or with a pair of prominent protuberances in the anterior margin of the pronotum and with the lateral border projected anteriorly ( B. trilobulicorne ). Dorsal surface sparsely punctate, sometimes with impressed medial furrow; lateral surface with moderately dense to dense punctation concentrated around the lateral fovea, on the anterior and posterior angles of pronotum, and along lateral margin. Scutellum: Triangular , length less than basal width ( Fig. 50); surface with punctures small, variable in density; lateral margin curving inward at base; basal margin slightly arcuate or straight; apex of scutellum subacute or rounded. Elytron: Convex; anterior margin not upturned; surface with 7 variably impressed striae between suture and humeral umbone; punctures small to moderate, separated by 1 or more puncture diameters; intervals smooth, only with micropunctures; second stria almost reaching elytral base. Ve n t e r: Surface with setation yellowish-brown or tawny brown, long, moderately dense, partially covering thorax and abdomen; abdominal sternites densely punctate. Prosternum posteriorly with apical tooth, dorsally with median carina. Mesocoxae subcontiguous. Metasternum pyriform, bulbous, convex medially, with median long metasternal carina; dorsally with small, dense punctures, partially covered by moderately dense, long setae; metasternal process anteriorly truncate. Legs: Protibia with 5 to 6 teeth on outer margin; teeth with acute or rounded apex; protibial spur subparallel, straight, acuminate at apex, length equals or exceeds the apex of the second protarsomere. Protarsus with first tarsomere longer than fifth, second to fourth tarsomeres decreasing in length. Mesotibiae and metatibiae robust, variably shaped in lateral view, but always with unlobed subapical carina and with knob-like projections randomly spread over surface above subapical carina. Male genitalia: Symmetrical, weakly sclerotized; aedeagus small, simple in structure, subparallel-sided; parameres short, basally membranous, with apex narrow distally, obtuse ( Fig. 53).

Female. As male except in the following respects. Head: trapezoidal; shorter than in male; dorsally without horns, but with a variably developed tubercle or tubercles on frontoclypeal region or frons; with a pair of short lateral carinae that converge distally. Clypeus truncate and elevated apically, dorsally rugulose. Pronotum: without anteromedian excavation, only with small concavity or depression located immediately behind of the apical margin of the pronotum. Female genitalia: not diagnostic.

Diagnosis. The following characters will separate Bolborhinum from all other South American Bolboceratini: head in the males with one to five horns of various forms and sizes ( Figs. 1 , 3, 4, 6, 7, 9, 11, 13); females without horns, only with a small tubercle situated near the frontoclypeal region or on the frons (Figs. 2, 5, 8, 10, 12, 14). Antennal club ovoid ( Fig. 47). Pronotum in males generally with deep and wide anteromedian excavation, dorsally with basal transverse ridge parallel to basal margin; females with a small concavity or depression located immediately behind the apical margin of the pronotum. Scutellum triangular. Elytron without basal margin or with weak basal margin, with 7 striae between medial suture and humeral swelling. Prosternal process prominent. Mesocoxae subcontiguous. Metasternum pyriform, bulbous, with median metasternal carina; metasternal process anteriorly truncate, not distinctly convex between mesocoxae. Protibial spur extending to apex of protibia. Mesotibia and metatibia with transverse ridge well separated from the distal apex, not subapical. Male genitalia: aedeagus small, simple in structure, subparallel-sided; parameres short, basally membranous, with apex narrow distally, obtuse ( Fig. 53).

Distribution. The species of this genus inhabit semiarid regions, including mixed Andean steppes with Araucaria trees and the Nothofagus forest habitats of southern South America ( Argentina and Chile). Bolborhinum occurs from sea level to high altitudes in the Andes Mountains (from 50– 2,500 m).

Taxonomic relations. Bolborhinum shares many characters with Halffterobolbus Martínez , Pereirabolbus , and Zefevazia ; these four genera are obviously closely related. Phylogenetic analyses and taxonomic revisions of the latter three genera are needed before the exact relationships and delimitations can be determined for all four of these Neotropical genera. Bolborhinum also appears to be closely related to the Australian genus Bolborhachium Boucomont. Both genera share a median anteriorly directed clypeal horn in some species, the outer segment of the antennal club usually more convex than the inner segment, the latter often nearly flat, the pronotum with a posterior transverse ridge, the scutellum with the lateral margin curving inward, the basal margin often sharply deflected downward, the sutural stria curving inward anteriorly and terminating near the apex of the scutellum , the prosternum posteriorly with an apical tooth, and the metasternal process often flat and anteriorly truncate ( Howden & Cooper 1977).

Nomenclature. The generic names Bolboceras Kirby and Bolborhinum Boucomont are both neuter in gender. Many species that were described in the genus Bolboceras over the past almost two centuries were erroneously given a masculine ending. Since most species currently classified in the genus Bolborhinum were originally described in the genus Bolboceras , several specific names need to be emended to agree in gender with Bolboceras and Bolborhinum , the genera they were originally and currently combined with. Several examples of this can be seen in the species treatments below.

Natural History. Little is known of the natural history of Bolborhinum species, and the larvae and pupae have never been described. We hypothesize that the larvae are mycetophagous. This would be congruent with observations made for North American and Australian members of the tribe Bolboceratini ( Howden 1955, Howden & Cooper 1977). The adults of the genus Bolborhinum appear mainly in early winter (July) and are active until autumn (May). Species of the genus Bolborhinum live in the proximity of forests and in clearings surrounded by low shrubs. The adults spend most of the time underground sheltered inside their burrows. At dusk, the males emerge to make circular flights at low height (10–30 cm) above the ground in search of females. Adults are largely nocturnal or crepuscular, and most species are moderately attracted to artificial light, especially to low intensity ultraviolet light (UV) (based on label data and personal observations). Some species of Bolborhinum concentrate many tunnels over a small surface area. They can construct galleries in sandy soil or sometimes can also be found in argillaceous, volcanic, or rocky soil. The adults dig a vertical tunnel of up to 1 m in depth, and sometimes the tunnel can be sinuous or otherwise not perfectly vertical. Lateral tunnels are constructed at the bottom of the main tunnels, presumably for larval burrows. The depth and direction of the tunnel seems to be influenced both by the type of soil and size of the beetle. Externally, the burrows are quite distinctive with small piles of fresh earth that are pushed to the surface and accumulate around the opening. Frequently it is possible to find more than one species of Bolborhinum sharing the same habitat.

Key to species of Bolborhinum ( B. seai females are unknown)

Note: females, particularly smaller or worn individuals, are very difficult to identify past couplet 9 of this key. Distribution, association with males, and examination of long series will all increase the chances of positively identifying female specimens.

1 Head dorsomedially with 4 tubercles forming trapezoid (broadest basally) (Figs. 19–20). Clypeal margin reflexed with two tubercles or teeth. Well-developed individuals with longitudinal carinae between head tubercles and sometimes joining the clypeal tubercles. Males and females...................... ............................................................................................. Bolborhinum laesicolle ( Fairmaire, 1856)

1' Head with prominent horns, with fewer than 4 tubercles, or with tubercles not forming trapezoid dorsomedially..............................................................................................................................................2

2(1') Head with 5 distinct horns (Figs. 24–25); 1 horn at clypeal apex, 2 clypeal horns on either side of midline towards base of clypeus (not on lateral margin), 2 frontal horns on either side of midline slightly apical to eyes. Known only from northern Argentina (Catamarca) ......................................................... ........................................................................................................ Bolborhinum seai ( Martínez, 1951)

2' Head with different horn configuration. Known only from central and southern Argentina (Mendoza to Río Negro) and Chile.........................................................................................................................3

3(2') Clypeus with distinct horn or horns (horns rarely worn down to look like tubercles, if so, wearing evident); apex of clypeus never with parabolic, blade-like carina. Males..................................................4

3' Clypeus without horns, with tubercles and carinae; apex of clypeus often with parabolic, blade-like carina ( Figs. 23, 27, 29, 31, 33, 35, 37). Females..................................................................................9

4(3') Head with a single, large clypeal horn ( Fig. 22); frontal horn/tubercle absent........................................ .......................................................................... Bolborhinum nasutum ( Fairmaire and Germain, 1861)

4' Head with multiple horns or tubercles..................................................................................................5

5(4') Head with 1 large apically projecting clypeal horn and 2 large horns originating from supraocular margin ( Figs. 30 , 32). Well-developed individuals with an additional pair of lateral processes on clypeal horn ........................................................................................ Bolborhinum tricorne ( Solier, 1851)

5' Head without large horns originating from supraocular margin............................................................6

6(5') Head with 4 distinct horns; 3 clypeal horns and 1 frontal horn forming a diamond ( Figs. 13, 36); 2 lateral clypeal horns not on margin ........................................ Bolborhinum tubericeps ( Fairmaire, 1856)

6' Head with less than 4 horns, or with 4 horns but with 2 lateral clypeal horns on margin....................7

7(6') Head laterally with distinct blade-like process or horn on margin (Figs. 26, 28) ................................... ............................................................................................ Bolborhinum shajovskoyi ( Martínez, 1952)

7' Head without distinct lateral processes or horns, all horns located on or next to midline.....................8

8(7') Head with two horns, basal horn located between eyes; apex of the clypeal horn trilobed, frontal horn bifurcate ( Fig. 34 ) ......................................................................... Bolborhinum trilobulicorne sp. nov.

8' Head with either 1 or 2 horns, neither horn between or near eyes; 1 prominent horn at midline of clypeal apex and either 2 tubercles directly behind it or with a distinct clypeal horn directly behind it (rear clypeal horn sometimes bifurcate) ( Figs. 15 , 17, 18) ...................................................................... ............................................................................................ Bolborhinum geotrupoides ( Laporte, 1840)

9(3') Pronotum with small, round depression at the apical margin; pronotum impunctate on medial third of disc.................................................................... Bolborhinum nasutum ( Fairmaire and Germain, 1861)

9' Pronotum without small, round depression at the apical margin; sometimes with longitudinal depression apically; pronotum punctate on medial third of disc; punctures small, sometimes concentrated near midline..........................................................................................................................................10

10(9') Supraocular margin elevated, cariniform, arcuate in posterior half (lateral view) ( Figs. 10, 31, 33)...... ....................................................................................................... Bolborhinum tricorne ( Solier, 1851)

10' Supraocular margin weakly elevated or not elevated...........................................................................11

11(10') Pronotum with thin, apical depression; pronotum with large punctures scattered unevenly across disc ............................................................................................. Bolborhinum tubericeps ( Fairmaire, 1856)

11' Pronotum with or without thin, apical depression at the apical margin; pronotal surface more evenly punctate; punctures typically small, dense...........................................................................................12

12(11') Head with clypeal tubercle elevated ( Figs. 8 , 27, 29), with prominent lateral cariniform processes. More common in Argentina, but also known from IX Región de La Araucanía, Chile.......................... ............................................................................................ Bolborhinum shajovskoyi ( Martínez, 1952)

12' Head with clypeal tubercle elevated or not elevated, without prominent lateral cariniform process. More common in Chile, but also known from Andean localities in Neuquén and Río Negro, Argentina..............................................................................................................................................................13

13(12') Pronotum anteromedially with furrow; dorsal surface with larger punctures concentrated laterally, at medial furrow, and on pronotal depression ................................... Bolborhinum trilobulicorne sp. nov.

13' Pronotum medially without furrow, anteromedially with weak depression at apical margin….............. ............................................................................................ Bolborhinum geotrupoides ( Laporte, 1840)

Clave para las especies de Bolborhinum Boucomont (la hembra de B. seai es desconocida)

Nota: las hembras, individuos particularmente más pequeños o gastados, son muy difíciles de identificar más allá del punto 9 de esta clave. La distribución, la asociación con los machos, y la revisión una serie numerosa aumenta las posibilidades de identificar positivamente los ejemplares femeninos

1 Cabeza dorsomedialmente con 4 tubérculos que forman un trapezoide (más amplio basalmente) (Figs. 19–20). Margen clipeal reflejado, con dos tubérculos o dientes. Individuos bien desarrollados con carenas longitudinales entre los tubérculos de la cabeza y el ápice clipeal. Machos y hembras ............. ............................................................................................. Bolborhinum laesicolle ( Fairmaire, 1856)

1' Cabeza con dos cuernos prominentes, con menos de 4 tubérculos, o con tubérculos que no forman un trapezoide...............................................................................................................................................2

2(1') Cabeza con 5 cuernos distintos (Figs. 24–25); 1 cuerno en el ápice clipeal, 2 cuernos clipeales a ambos lados de la línea media en la base del clípeo (no en el margen), 2 cuernos frontales a ambos lados de la línea media y ligeramente apical de los ojos. Conocida sólo del norte de Argentina (Catamarca)............................................................................................. Bolborhinum seai ( Martínez, 1951)

2' Cabeza con diferente configuración de cuernos. Conocida sólo del centro y sur de Argentina (Mendoza a Río Negro) y en Chile.................................................................................................................3

3(2') Clípeo con un cuerno o cuernos distintos (cuerno evidente, raramente bajo como tubérculo); ápice del clípeo nunca con carena laminar parabólica. Machos............................................................................4

3' Clípeo sin cuernos, con tubérculos y carenas; ápice del clípeo a menudo con carena laminar parabólica ( Figs. 23, 27, 29, 31, 33, 35, 37). Hembras..........................................................................9

4(3') Cabeza con un único y largo cuerno clipeal ( Fig. 22); cuerno frontal/tubérculo ausente ....................... ............................................................................. Bolborhinum nasutum ( Fairmaire y Germain, 1861)

4' Cabeza con múltiples cuernos o tubérculos...........................................................................................5

5(4') Cabeza con 1 cuerno clipeal largo apicalmente proyectado, y 2 cuernos largos que se originan en el margen supraocular (Fig. Figs. 30 , 32). Individuos bien desarrollados con un par adicional de procesos laterales en la base del cuerno clipeal ..................................... Bolborhinum tricorne ( Solier, 1851)

5' Cabeza sin cuernos largos originados en el margen supraocular...........................................................6

6(5') Cabeza con 4 cuernos distintos; 3 cuernos clipeales y 1 cuerno frontal formando las esquinas de un diamante ( Figs. 13, 36); 2 cuernos clipeales laterales no situados en el margen..................................... ............................................................................................. Bolborhinum tubericeps ( Fairmaire, 1856)

6' Cabeza con menos de 4 cuernos, o con 4 cuernos pero con 2 cuernos laterales en el margen..............7

7(6') Cabeza lateralmente con distinto proceso o cuerno en el margen (Figs. 26, 28)..................................... ............................................................................................ Bolborhinum shajovskoyi ( Martínez, 1952)

7' Cabeza sin proceso lateral o cuerno, todos los cuernos ubicados en o después de la línea media.......8

8(7') Cabeza con 2 cuernos, cuerno basal ubicado entre los ojos; ápice del cuerno clipeal trilobulado, cuerno frontal bifurcado ( Fig. 34 )................................................. Bolborhinum trilobulicorne sp. nov.

8' Cabeza con 1 o 2 cuernos, ningún cuerno entre o cerca de los ojos; 1 cuerno prominente en la línea media del ápice clipeal y 2 tubérculos ubicados detrás de él o con un cuerno clipeal distinto ubicado detrás de él (cuerno clipeal posterior a veces bifurcado ( Figs. 15 , 17, 18) ............................................. ............................................................................................ Bolborhinum geotrupoides ( Laporte, 1840)

9(3') Pronoto con depresión pequeña y redondeada en el margen anterior; pronoto sin puntuación en el tercio medio del disco........................................... Bolborhinum nasutum ( Fairmaire and Germain, 1861)

9' Pronoto sin depresión pequeña y redondeada en el margen apical; a veces con depresión apicalmente longitudinal; pronoto punteado en el tercio medio del disco; puntuación pequeña, a veces concentrada cerca de la línea media........................................................................................................................10

10(9') Margen supraocular elevado, careniforme, arqueado en la mitad posterior (vista lateral) ( Figs. 10, 31,

33) ................................................................................................. Bolborhinum tricorne ( Solier, 1851) 10' Margen supraocular débilmente elevado o no elevado........................................................................11

11(10') Pronoto con ligera depresión apical; pronoto con puntuación grande dispersa irregularmente alrededor del disco ........................................................................ Bolborhinum tubericeps ( Fairmaire, 1856)

11' Pronoto con o sin depresión ligera en el margen apical; superficie pronotal completamente punteada, uniforme; puntuación tipicamente pequeña, densa..............................................................................12

12(11') Cabeza con tubérculo clipeal elevado ( Figs. 8 , 27, 29), con procesos laterales careniformes, prominentes. Más común en Argentina, pero también conocida de la IX Región de La Araucanía, Chile...... ............................................................................................ Bolborhinum shajovskoyi ( Martínez, 1952)

12' Cabeza con tubérculo clipeal elevado o no elevado, sin procesos laterales careniformes. Común en Chile, pero también conocido de localidades andinas en Neuquén y Río Negro, Argentina...............13

13(12') Pronoto anteromedialmente con surco; superficie dorsal con puntuación gruesa concentrada lateralmente, en el surco, y en la depresión pronotal.............................. Bolborhinum trilobulicorne sp. nov.

13' Pronoto medialmente sin surco, anteromedialmente con ligera depresión en el margen apical.............. ............................................................................................ Bolborhinum geotrupoides ( Laporte, 1840)

Figures

FIGURE 1. Bolborhinum geotrupoides male in lateral view. FIGURE 2. Bolborhinum geotrupoides female in lateral view. FIGURE 3. Bolborhinum laesicolle in lateral view.

FIGURE 8. Bolborhinum shajovskoyi female in lateral view.

FIGURE 15. Bolborhinum geotrupoides male in dorsal view. FIGURE 16. Bolborhinum geotrupoides female in dorsal view. FIGURE 17. Bolborhinum geotrupoides male head.

FIGURE 30. Bolborhinum tricorne male in dorsal view. FIGURE 31. Bolborhinum tricorne female in dorsal view. FIGURE 32. Bolborhinum tricorne male head.

FIGURE 34. Bolborhinum trilobulicorne male in dorsal view. FIGURE 35. Bolborhinum trilobulicorne female in dorsal view. FIGURE 36. Bolborhinum tubericeps male in dorsal view.