Cephalissa is a monotypic moth genus in the family Geometridae. Its only species, Cephalissa siria, the orange triangle moth, is endemic to New Zealand. This species has been classified as nationally vulnerable by the Department of Conservation. It has suffered a contraction of its range, no longer being seen in Dunedin or Invercargill. It is currently found in the Mt Watkin Scenic Reserve, in eastern Otago, in the Rongahere Gorge and in the Dansey Ecological District. C. siria is known to inhabit kahikatea forest amongst Carex species as well as short tussock grasslands and shrubland. The larval host plant is Fuchsia perscandens. Adult moths are on the wing in October and November.

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