|A live individual of Papilio macilentus|
|Museum specimen of Papilio macilentus, dorsal view|
Papilio macilentus, the Long Tail Spangle, is a species of butterfly belonging to the family Papilionidae.
The wingspan of Papilio macilentus reaches about 9–12 millimetres (0.35–0.47 in). Wings are black, with red spots, wavy edges and long tails on its hind wings. At the outer edge of the hind wings there is row of small red spots, while at the inner edge there is a red eye. This species has the longest tail in the family Papilionidae. Males have a yellow transversal band in the overlapping part between the fore wings and the hind wings.  The underside of the forewings is dark-brown, with black veins. The thorax , the head and the abdomen are black. 
The spring type is found from April to June, and the summer type from July to August. During daytime, females fly low and lay eggs one by one on the leaves of the plants. The larvae feed on Rutaceae species (Orixa japonica, Poncirus trifoliata, Ruta graveolens, Zanthoxylum ailanthoides, Zanthoxylum piperitum, Zanthoxylum schinifolium).  The species hibernates in the pupal stage.
Distribution and habitat
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- GloBIS (GART): Global Butterfly Information System. Häuser C., Holstein J. & Steiner A. (eds).
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