Zeugma (planthopper)

Species of the genus Zeugma are found in central and western parts of Indonesia, in Malaysia, Thailand, Cambodia, the Philippines, Taiwan and in Assam (India). The description of the type species of Zeugma, Zeugma vittata, was based on a specimen of unknown origin.^[11] In 1913, Muir described Zeugma monticola which he later regarded as a synonym name for Zeugma vittata, giving Parit Buntar (peninsular Malaysia), Mowong (Borneo) and Pekalongan (Central Java) as localities.^[3] Four other species of Zeugma have been described by Muir from Indonesia, Zeugma elegans and Zeugma karnyi from the Mentawai Islands, off West Sumatra, Zeugma corporaali from Medan in northern Sumatra, and Zeugma javana from Java.^[12][13][4] In addition, Zeugma fuscinervis has been described from Assam (India), Zeugma valdezi from the Philippines, as well as two species from Taiwan (Zeugma maesta and Zeugma makii).^[6][7][8] Several unidentified species of Zeugma have been reported from southern Thailand, southern Cambodia and from Sulawesi Island in Indonesia.^[5]

Typically, species in the tribe Zoraidini have forewings which are at least 3½ times longer than wide, hind wings which are less than half as long as the forewings and a media vein on the forewings which has 5 or 6 branches.^[10] In the genus Zeugma the above features do not apply. The forewings are broader, only about 2½ times longer than wide, the hind wings are longer than half the forewing length, usually around 60% of the forewing length, and the media vein on the forewing has 8 or more branches, usually with none of them branching further into sub branches. Such features are found in the tribe Derbini and Zeugma has been placed into that tribe before the 1950s.^[9] However, Zeugma was transferred to the tribe Zoraidini by Fennah after redefining the tribe Zoraidini. This transfer was mainly based on the venation of the forewings, specifically that of the clavus and the cubitus, as well as on the venation of the hind wings. Like in other genera of Zoraidini, the forewings of Zeugma have an open clavus where the two veins of the clavus join, but the combined vein does not reach the hind margin, instead it meets the veins of the cubitus.^[10]

When live Zeugma species are at rest, they carry their wings in a roof-like position covering their abdomen.^[5] This is also in contrast to most other species of the tribe Zoraidini which raise their wings above the body.^[14] Both wing positions are not found in species of the tribe Derbini, which spread out their wings laterally when at rest, holding them parallel to the surface they sit on.^[10][15] Due to the various differences to other genera in the tribe Zoraidini, the genus Zeugma has been placed in a separate subtribe, the Zeugmatina.^[16]

Within the tribe Zoraidini, the species of Zeugma are of medium size, the body is around 5 mm long from the tip of the head to the end of the abdomen. The forewings are usually around 9 mm long.^[3][6] Zeugma elegans appears to be the largest species with a body length of 6 mm and a forewing length of 13 mm.^[4] The head is broad, as broad as the thorax, another unusual feature in the tribe Zoraidini. The dorsal part of the head between the eyes (the vertex) and the face are also broad. The antennae are elongated, but shorter than the face.^[10] The typical colour of Zeugma species is light brown or stramineous (straw-coloured), often with dark brown marks or bands. For example, the forewings or the mesonotum might have dark brown bands. The forewing veins are also often dark brown or are lined with dark brown stripes. Further, the body and legs can have additional marks which may be black, red or yellowish.^[3][4][5]