Orthobrachia Warren, 1895

Huang, Guo-Hua, Su, Zi-You & Stuening, Dieter, 2016, Taxonomic notes on the genus Orthobrachia Warren, with description of a new species from China and Thailand (Lepidoptera, Geometridae), ZooKeys 609, pp. 121-137 : 122-123

Taxon classification Animalia Lepidoptera Geometridae

Orthobrachia Warren, 1895

Orthobrachia Warren, 1895. Novit. zool. 2: 121. Type species: Stegania latifasciata Moore, 1888 by original designation. In: Hewitson & Moore, Descr. new Ind. lep. Insects Colln late Mr. Atkinson: 260. [Type specimen: Lectotype, male, Darjeeling in India (BMNH, London), designation by Yazaki in Haruta, 1992]

Description and diagnosis.

Head. Male antennae shortly and stiffly bipectinate to three-fourths or four-fifth, rami unscaled on dorsal side, flattened and distally slightly clubbed, arising ventrally from about the middle or the proximal one third of the flagellomers. Female antennae filiform. Frons narrow, flat, smooth-scaled. Palps delicate, slightly curved upward, reaching just beyond frons. Basal segment rough-scaled, second segment smooth-scaled, terminal segment very small. Haustellum well developed. Thorax. Hind leg tibia not dilated, without scent-brush. Index of spurs 0-2-4. Forewings without fovea; common stalk of veins R2-R5 arising at large distance from the upper corner of the cell (= origin of M1) in forewing, very close to the origin of vein R1 which anastomoses with Sc. In hindwing vein Rs also at large distance from M1. Abdomen with tergites and sternites weak, membranous, only tergites 1 and 2 and sternites 1+2 may be slightly sclerotized. Sternite 3 without setal comb. Tympanal organs rather large, globular, without laciniae.

Characters indicating Orthobrachia to be a distinct genus are found in the male genitalia: Elongated, spined or densely setose lobes arising from dorsal margin of sacculus near its base are present in all species of Orthobrachia , but are not found in other genera of Baptini . The valves are elongated, more or less parallel-sided, with rounded apex, curved upward in all species except Orthobrachia simpliciata , with a broad, immaculate zone with one or two processes of different shape; valve lamina with an elongated field of setae; gnathos weak, only lateral arms present; juxta a broad, oval, somewhat elongate plate, ventrally angled and with v-shaped incision distally; aedeagus with bulbous caudal end, curved or straight, with one or two large cornuti on vesica, in two species with a bunch of external cornuti or a long row of small cornuti.

The female genitalia also indicate the distinctness of Orthobrachia , though their characters separate two species-groups: 1) the latifasciata -group, also containing flavidior , tenebrosa and owadai : their genitalia are characterized by a well sclerotized antrum with distal and/or lateral processes, continued into a long, sclerotized band that reaches deeply into the bursa copulatrix. Signum a large, ring-like structure without dentation; 2) the simpliciata -group with semicircular lamellae antevaginales, without long sclerotized bands and with a stellate signum. Orthobrachia simpliciata exhibits the most plesiomorphic characters in the female, but also in the male genitalia.

Host-plant.

Unknown.

Distribution.

Oriental Region. The distributional map of all the known species is provided in Figure 1.

Key to the species of the genus Orthobrachia

(based on wing pattern and colouration)