Oncocephala acutangula Gestro, 1917

Calcetas, Orlando A., Staines, Charles L., Adorada, Jessamyn R., Calilung, Venus J., Caoili, Barbara L. & Jamias, Serlie B., 2021, Review of the Genus Oncocephala Agassiz, 1846 (Coleoptera: Chrysomelidae: Cassidinae: Oncocephalini) in the Philippines, The Coleopterists Bulletin 75 (2), pp. 445-458 : 447-449

Oncocephala acutangula Gestro, 1917 ( Figs. 1–5 )

Oncocephala acutangula Gestro 1917: 404 . Type locality: Philippines, Mindanao , Davao; type depository (holotype): MSNG.

Redescription (n = 3). Length = 4.8–5.3 mm (apical margin of head to apex of elytron), width = 2.5–3.0 mm (middle of elytra). Head, pronotum, elytra and legs pale brown with black tinge; antennae black with dark brown tinge, pale brown towards apex ( Fig. 1 ). Head. Compound eyes conical dorsally, vertex with two rounded pits on each side; dorsal cephalic horn pear-shaped, anterior half distinctly narrower than posterior half in dorsal aspect ( Fig. 2 ), narrowing towards anterior margin, boat-shaped and elongate in lateral aspect ( Fig. 3 ), wedge-shaped anteriorly, rounded posteriorly; with cephalic horn formula of 6 (2-2-2). Antenna. 1.5× length of pronotum; antennomeres 1 and 2 broader apically; antnenomere 3 distinctly longer than 4; antennomeres 4–5 broader apically; antennomeres 7–10 quadrate; antennomere 11 conical, distinctly elongate, slender; antennomere 1 without striation, 2–11 with striation, 2–6 broadly striate, 8–11 finely striate.Antennal length 3.2 mm. Pronotum. Longer than wide; anterior margin almost straight medially; lateral protuberance equilateral, small, with narrow basal margin posterolaterally; lateral margin slightly convex medially; anterior angle obtuse, posterior angle acute; posterior margin concave laterally, almost straight medially, each side and medial margin broadly carinate; with two subapical conical tubercles; medial longitudinal cavity interrupted medially by a callosity; pronotal width 1.1 mm; pronotal length 2.0 mm. Scutellar shield. Anterolateral margin wedge-shaped, lateral margin straight, apically rounded. Elytron. Humeral margin with 4 distinct, minute tubercles near scutellar shield (scutellar tubercles); with tubercle on costa II (elytral tubercle 1), and a tubercle between costae II and III (elytral tubercle 2); humeral tubercle (elytral tubercle 3) small, almost equal in size to elytral tubercle 1; lateral margin distinctly broader apically with pronounced medial sinuation and large, irregularly spaced teeth; exterior apical angle acute, ≤45°, distinctly elongate laterally; apical margin wedge-shaped, dentate; sutural angle angulate, almost 90°; with 10 distinct elytral tubercles; tubercle 1 on costa I small, conical; costa II with 5 distinct tubercles: T1 moderate, equilateral, rounded apically, connect- ed to T2 basally; T2 moderate, equilateral, with short, almost truncate apical margin, coalesced, connected to T3 subapically; T3 large, scalene, rounded apically, connected to T4 basally; T4 and T5 small, convex, coalesced, connected to each other subapically; minute tubercles present between tubercles: one tubercle between T1 and T2, four between T2 and T3, two between T4 and T5; costa III with 1 distinct tubercle: T1 small, equilateral, rounded apically; costa IV with 3 distinct tubercles: T1 moderate, equilateral, rounded apically, with broad basal margin; T2 moderate, conical and T3 small, conical; costa V without distinct tubercles, costal margin near sutural angle connected to costal margin of T5 of costa II; elytral tubercle formula 10 (1-5-1-3-0); elytron width 1.3–1.5 mm medially; elytron length 3.0– 3.5 mm. Leg. Femur not rugose or tuberculate ( Figs. 1, 4 , 5 ).

Material Examined. Holotype. Philippines: MINDANAO: Davao, Baker (1, MSNG) . Other material. Philippines: LUZON: Mindoro: Mt. Calavite , W. Schultze (1, SDEI-09716 ) ; VIZAYAS: Leyte: San Jose , stagnant pool, 26-xi-1944, E. Rey (1, MGFT) ; Leite: Tacloban, 1940, Linke Becke (1, SDEI-09714 ) ; Panay: Jamindan (1, SDEI-09715 ) .

Distribution. Philippines (Luzon, Visayas).

Remarks. This species can be distinguished from all other species of Oncocephala in this study by having the exterior apical angle of elytra acute, ≤45°, while it is almost 90° in all other species. The teeth on the lateral margin of the elytra are tapered apically and more pronounced in O. acutangula , while apically rounded and less pronounced in all other species.

The overall dorsal aspect of the cephalic horn of O. acutangula , O. bicristata , O. angulata and O. philippinica is pear-shaped while it is ovoid in O. polilloana . The anterior half of the same in O. acutangula , O. bicristata , O. angulata and O. philippinica is distinctly narrower than the posterior half, while it is almost as broad in O. polilloana .

The elytron has the largest number of tubercles on costa II, namely 5, and tubercles 4 and 5 of costa II coalesce subapically.Along with O. philippinica , O. acutangula has a total of 10 distinct elytral tubercles. The variation of characters observed within the species are as follows: the lateral teeth of the elytra are larger and more pointed than in other species and the exterior apical angle of the elytron ≤45°.

Figures

Figs. 1–4. Oncocephala acutangula. 1) Habitus, dorsal aspect; 2) Cephalic horn, dorsal aspect; 3) Cephalic horn, lateral aspect; 4) Habitus, lateral aspect.

Fig. 5. Oncocephala acutangula holotype habitus, dorsal aspect (photograph from MSNG, courtesy of R. Poggi).