Arcastes dimidiata Laboissière, 1929

Hazmi, Izfa Riza & Wagner, Tomas, 2010, Revision of Arcastes Baly, 1865 from the Oriental Region (Coleoptera, Chrysomelidae, Galerucinae), ZooKeys 42 (42), pp. 79-99 : 95-97

Arcastes dimidiata Laboissière, 1929

Arcastes dimidiata Laboissière, 1929: 92 .

Total length. 4.70–6.80 mm (mean: 5.85, n=5)

Head. Reddish-brown to red. Details of mouthparts and impressions on vertex like the description of the genus. Basal two and terminal two to three antennomeres yellowish-red, some specimens also with black antennal base (Figs 18, 19). Shape of antennomeres like description of the genus, but median antennomeres less enlarged. Ratio length of second to third antennomere 0.50–0.57 (mean: 0.53), ratio length of third to fourth antennomere 0.60–0.70 (mean: 0.66; Fig. 20 ).

Thorax. Shape and coloration of pronotum and scutellum like in the description of the genus (Figs 18, 19). Pronotal width 1.70–2.20 mm (mean: 1.99 mm), ratio length to width 0.53–0.55 (mean: 0.54). Basal third of elytra entirely reddish-brown to red, apical two third black (Figs 18, 19). Elytral length 4.00– 5.90 mm (mean: 5.04 mm), maximal width of both elytra together 2.90–4.00 mm (mean: 3.46 mm), ratio of maximal width of both elytra together to length of elytra 0.66–0.70 (mean: 0.68). Underside and legs like in the description of the genus, some specimens also with reddish femur.

Abdomen. Pale yellow to brown, occasionally darker on middle, and last sternite usually dark brown to black.

Male genitalia. The outer shape as in the description of the genus. Endophallus with three spurs located at the upper part, the biggest one next to the lateral spiculae. Tectum not incised at apex, slender, almost reaching towards the apex of the median lobe (Fig. 21).

Female genitalia. Spermatheca with oval to elongated nodulus. Middle part more less long and slightly curved, cornu long and curved ( Fig. 22 ).

Distribution. Recorded from Sabah (Borneo) and western Sumatra ( Fig. 6).

Diagnosis. Arcastes dimidiata can be easily differentiated from A. biplagiata and A. suturalis by the elytral coloration. The basal elytral third is reddish and strongly contrasting with the black two terminal thirds, while it possess neither a pale suture nor elytral spots (Figs 1, 11, 18).

Type material. Holotype, 1 ♁, “ Siberut Island , West Sumatra, Sept. 1924, G. B. K and N. S, Arcastes dimidiata Laboissière, 1929 ” (Fig. 19) ( BMNH) . Holotype by monotypy. Type locality: 1°55'S / 99°17'E.

Further material examined. Malaysia. 1 ex., N. Borneo, Samawang, Nr. Sandakan, 14th July. 1927, Ex. F. M. S. Museum. B. M. 1955–354, 5°50'N / 118°6'E

Figure |8. Arcastes dimidiata Laboissière, 1929 . Dorsal colour pattern.

( BMNH); 2 ex., N. Borneo, Mt. Kinabalu , Pinosuk Plateau, 14.–17.III.1964, 5,225 ft, Royal Soc. Exped., col. S. Kueh, B. M. 1964–250, 6°4'N / 116°33'E ( BMNH) ; 1 ex., Borneo. Kinabalu, Jacoby Coll. 1909–28 a, 6°4'N / 116°33'E ( BMNH) .

Figure |9. Arcastes dimidiata Laboissière, 1929 . Photographs of the holotype A. dimidiata Laboissière, 1929 : a with labels b detail.

a

b

Figures

Figure 20. Arcastes dimidiata Laboissière, 1929. Antennae: a male b female.

Figure 22. Arcastes dimidiata Laboissière, 1929. Two different spermathecae.