Lemon butterfly is

Lemon butterfly is Papilio demoleus.
Papilio demoleus is a widespread swallowtail butterfly. The butterfly is also known as the lime butterfly, lemon butterfly, and chequered swallowtail.
This butterfly is an avid mud-puddler and visitor of flowers. It basks with its wings held wide open on tufts of grass and herbs, and generally keeps within a metre of the ground, even on cloudy days.
The female butterfly goes from plant to plant, laying a single egg at a time on top of a leaf, which it holds onto with its legs, and flies off as soon as the egg is laid. The egg is round, light yellowish, flattened at the base, smooth-surfaced, and about 1.5 mm in height. Fertile eggs develop a small red mark at the apex.