Chaetocnema (Chaetocnema) trapezoida Ruan, Konstantinov & Yang, 2019

Ruan, Yongying, Yang, Xingke, Konstantinov, Alexander S., Prathapan, Kaniyarikkal D. & Zhang, Mengna, 2019, Revision of the Oriental Chaetocnema species (Coleoptera, Chrysomelidae, Galerucinae, Alticini), Zootaxa 4699 (1), pp. 1-206 : 110-113

43. Chaetocnema (Chaetocnema) trapezoida Ruan, Konstantinov & Yang , New Species

( Figs. 64 , 65 )

Etymology: This species is named after its trapezoidal pronotum. Specific epithet is a noun in apposition.

Distribution: Thailand.

Diagnosis: Based on the original description ( Duvivier, 1892), C. nagpurensis Duvivier and C. trapezoida sp. nov. resemble each other superficially. However, they may be easily distinguished from each other by the body col- or. Chaetocnema nagpurensis is somewhat darker with head, prothorax and elytra bronzy, while pronotum and head in C. trapezoida are obviously metallic green. Interspaces between puncture rows of elytra are densely punctate and transversely wrinkled in C. nagpurensis , the same is finely punctate and not wrinkled (or only slightly wrinkled on peri-scutellar area) in C. trapezoida .

Host plants: Unknown.

Description: Body length: 2.15–2.25 mm. Body width: 1.20–1.25 mm. Ratio of length of antenna to length of body: 0.57–0.60. Ratio of elytron length (along suture) to width (maximum): 2.45–2.50. Ratio of pronotum width (at base) to length: 1.65–1.68. Ratio of length of elytron to length of pronotum (along middle): 2.25–2.35. Ratio of width of elytra at base (in middle of humeral calli) to width of pronotum at base: 1.00–1.05.

Pronotum and head metallic green. Elytra metallic green to bronzy brown. Pronotum and head finely reticulate. Antennomeres 1–6 completely yellow brown, 7–11 brown. Tarsi and tibiae yellow brown. Pro- and mesofemora light brown. Metafemur dark brown.

Head hypognathous. Frontal ridge wide, flat. Frontolateral sulcus present. Suprafrontal sulcus poorly developed, frons more or less merge with vertex. Orbital, supraantennal sulci poorly developed. Ratio of width of frontal ridge (excluding margin) to width of antennal socket (excluding margin): 2.20–2.30. Sides of vertex covered with numerous shallow and medium sized punctures, leaving a longitudinal area in middle impunctate. Number of punctures on vertex: 45–55 on each side of vertex. Number of punctures on orbit: 2–4 on each side. Number of punctures on frons (triangular area surrounded by frontolateral sulcus and clypeus): 0. Number of setae on clypeus: approximately 10-15. Number of setae on labrum: 6. Anterior margin of labrum slightly convex at middle.

Pronotum without longitudinal impressions near basal margin. Deep transverse row of large punctures at base of pronotum present laterally, absent at middle. Pronotal base convex, with middle expanded. Lateral margins of pronotum almost straight, converging forward.Anterolateral prothoracic callosity almost absent, slightly developed along lateral margin. Posterolateral prothoracic callosity poorly developed. Diameter of pronotal punctures 1.5–3 times smaller than distance between them.

Elytra with slightly convex lateral sides. Elytral punctures larger than those on pronotum. Punctures on elytron arranged in single rows, including peri-scutellar row. Elytral interspaces between puncture rows slightly costate at sides. Number of rows of minute punctures on each interspace: 2–3. Humeral callus moderately developed.

First male protarsomere slightly larger than second. Excavation on metatibia moderately deep. Large lateral denticle on metatibia sharp. Metatibial serration proximal to large lateral denticle absent or poorly developed.

Apex of aedeagus in ventral view narrowing gradually. Ventral longitudinal groove absent or poorly developed. Apical denticle in ventral view absent. Minute transverse wrinkles on ventral side absent. Aedeagus in lateral view evenly and slightly curved, somewhat sinusoidal near apex.

Types: Holotype: ♂ ( BMNH), labels: 1) Siam: Bankok, H. Hillman, B. M. 1928–366; 2 ) Holotype Chaetocnema trapezoida sp. nov. Des Yongying Ruan et al., 2016.

Paratypes: 1♂ (BMNH), labels: 1) Siam: Bankok, H. Hillman, B. M. 1928–366; 2) Paratype; 3) Chaetocnema trapezoida sp. nov. Des Yongying Ruan et al., 2016. 1♂ (USNM), labels: 1) Thailand: Kanchanasuri, alt. 50m, 28.vi.1989, V. Kuban leg.; 2) Chaetocnema singala Maulik, 1926 , det. Ruan, 2016; 3) Chaetocnema trapezoida sp. nov. Des Yongying Ruan et al., 2016.

Figures

FIGURE 64. Chaetocnema trapezoida sp. nov. Male habitus (hand drawing).

FIGURE 65. Chaetocnema trapezoida sp. nov. A Holotype (male), habitus. B Pronotum and peri-scutellar area of Holotype. C Head of Holotype, frontal view. D Aedeagus of Holotype, ventral view. E Aedeagus of Holotype, lateral view. F Apex of aedeagus of Holotype, ventral view.