Triodontus bicavatus ( Fairmaire, 1905 )

Frolov, Andrey V., Montreuil, Olivier & Akhmetova, Lilia A., 2016, Review of the Madagascan Orphninae (Coleoptera: Scarabaeidae) with a revision of the genus Triodontus Westwood, Zootaxa 4207 (1), pp. 1-93 : 66-68

Triodontus bicavatus ( Fairmaire, 1905)

( Figs. 33 A–H)

Orphnus bicavatus Fairmaire, 1905: 118 .

Triodontus bicavatus (Fairmaire) : Paulian 1977: 1221. Triodontus obsoletus Brancsick : synonymy by Paulian 1977.

Type material examined. Holotype ( Figs. 33 A, D), male, “MUSÉUM PARIS 1906 Coll. Leon Fairmaire / Orphnus bicavatus opm n. sp. XXX / TYPE” (MNHN)

Additional material examined. MADAGASCAR. Antsiranana: one male, “ Mt. d'Ambre [Amber Mountains, 12°31′50″S, 49°10′24″E] / Museum Paris 1934 Brouhard ” ( MNHN); one male, “Mad. Vohemar, Ampanefena XII.36 Vadon [Vohemar, Ampanefena, 13°52′00″S, 49°58′00″E]” ( MNHN) ; one male, “ Diego Suarez [12°16′00″S, 49°16′59″E] / Museum Paris 1936 Coll. A. Boucomont” ( MNHN) ; four males, five females, “ Andapa / Madagascar Ron Antalaha XII.37 Vadon [Antalaha District, Andapa, 14°39′00″S, 49°39′00″E ” ( MNHN); four males, nine females, “ Madagascar-Est dct. Sambava R.N. XII-Marojejy Ambatosoratra 1700m XI-60 P.Soga [Ambatosoratra, Natural Reserve of Marojejy (RNI XII), 1700 m, 14°25′59″S, 49°43′59″E]” ( MNHN) ; seven males, 10 females, “ Madagascar Ron Antalaha XII.35 Vadon Andapa [Antalaha District, Andapa, 14°39′00″S, 49°39′00″E]” ( MNHN) ; 10 males, 32 females, “ Mt. d'Ambre [Amber Mountains] Madagascar ” ( MNHN) ; one male, “ Madagascar Nord Montagne D'Ambre Foret de Sakaramy 28.XII.2005 A.Ballerio ” ( ABCB) ; Mahajanga: three males, “ Anginjanbary [dubious locality] / Madagascar Ron Mandritsara XII-37 Vadon!” ( MNHN) .

Diagnosis. Triodontus bicavatus is most similar to T. nitidulus . Males of the former species can be separated by having abdominal sternite 8 rather wide, not sinuate medially, and with oval transverse concavity, and also by having the lateral lobes of the parameres with small keel-shaped processes on proximal parts. Females of these species are difficult to separate.

Description. Male. Color of head, pronotum, and elytra dark brown; legs, antennae, and underside of the body brown ( Figs. 33 A–B).

Frontoclypeus convex anteriorly, rounded laterally, anterior margin crenulate and setose in dorsal view. Eyes relatively small (diameter slightly smaller than the distance between eye and gula in ventral view), incompletely divided by canthus into small, dorsal and large, ventral parts. Frontoclypeus with small tubercles mediad of each eye and in some specimens with a horn in the center of the frontoclypeus. The horn, when the most developed, is about as long as the width of the head, acutely rounded apically, straight to somewhat curved caudally at the apex, slightly rugose on posterior side.

Pronotum with a bulge medially, with excavations aside the bulge, and with 2 ridge-shaped tubercles laterally of each excavation. The median bulge has 3 small but distinct tubercles. Lateral margins with wide border appearing somewhat crenulate in dorsal view, with a row of brown setae. Anterior margin with wide, smooth border. Posterior margin with fine border, not crenulate, punctate with narrow longitudinal punctures. Surface of most pronotum smooth, anterior and posterior angles with sparse and coarse punctation.

Scutellum rounded apically, its visible part is about 1/12 length of elytra.

Elytra convex, with distinct humeral humps, their maximum width is approximately at the middle. Elytra with 10 distinct striae on disc and with oblique line from base of 6th stria to approximately middle of 8th stria. Stria with small punctures. Intervals with minute punctures, almost smooth. Base of elytra with an irregular row of coarse punctures.

Sternite 8 medially feebly sinuate (in ventral view), with elongate transversal fovea ( Fig. 33 G).

Parameres ( Fig. 33 F) with large outer lobes covering inner lobes (in lateral view). Proximal parts of outer lobes with small keel-shaped processes. Internal sac of the aedeagus with 1 strongly-sclerotized, somewhat horseshoeshaped, symmetrical sclerite and with 2 similar protuberances of the membrane ( Fig. 33 E).

Female. Females ( Fig. 33 C) differ from males in having long apical spur on protibiae, absence of head and pronotum armature including tubercles mediad of each eye, densely punctate dorsal side of head, and longer abdominal sternites including 6th sternite, which is evenly rounded apically.

Variation. The variation is similar to that of T. nitidulus : pronotal and head armature of males is subject to allometric variability from fully developed (as described above) to almost undeveloped (with the males having small frontoclypeal tubercles in the middle and small fossa on the pronotum anteriorly). Body length of examined specimens varied from 6.5–8.2 mm (males) and from 6.5–7.5 mm (females).

Remarks. Paulian (1977) considered O. obsoletus a junior synonym of T. bicavatus , however the type specimen of the former species has all the diagnostic characters of T. nitidulus (see above).

Distribution. T. bicavatus is known from a few localities in northern Madagascar including the northernmost part of the island ( Fig. 33 H).

Figures

FIGURE 33. Triodontus bicavatus. Habitus in dorsal view (A, B—male [A—holotype], C—female), labels of holotype (D), internal sac of aedeagus (E), aedeagus in lateral view and parameres in dorsal and ventral view (F), abdomen of holotype (G), distributional records (H).