Papilio demoleus is a common and widespread swallowtail butterfly. This species is found throughout tropical and subtropical regions of southern Asia. The butterfly is also known as the common lime butterfly, lemon butterfly, lime swallowtail, small citrus butterfly, chequered swallowtail, dingy swallowtail and citrus swallowtail. These common names refer to their host plants, which are usually citrus species such as the cultivated lime. Unlike most swallowtail butterflies, it does not have a prominent tail. Lime is a common butterfly and commonest among swallow tails in NEERI campus.

This butterfly ranges widely and is an extremely successful invader. Its proliferation appears to be aided by agricultural land use and urbanization that creates new, suitable open habitat and enhanced availability of host resources.

The adults range in wingspan from 80-100 mm. The hind wing has no tail. The upper portion of the forewing is largely black and the outer wing margin has a series of irregular yellow spots. Two yellow spots are present at the upper end of the discal cell with several scattered yellow spots in the apical region. The upper hind wing has a red tornal spot and the discal black band is dusted with yellow scales. The underside is paler yellow with the black areas more heavily dusted with yellow. The adults fly in every month but are more abundant after monsoons.

P. demoleus feeds on plants in the Rutaceae/Lime family. It is known to feed on virtually all species and varieties of native or introduced citrus (including cultivated members of the genus Citrus), Aegle marmelos (Bael fruit), Murraya (Indian curry-leaf tree) etc.