Mud puddling

Mud-puddling is the phenomenon mostly seen in butterflies and involves their aggregation on substrates like wet soil, dung and carrion to obtain nutrients such as salts and amino acids.
This behavior is restricted to males in many species. In tropical India this phenomenon is mostly seen in the post-monsoon season. The groups can include several species often including members of the Papilionidae and Pieridae. Following pictures were captured from the banks of Bhavani river in South India of Common Lime Butterfly(Papilio demoleus). 

Common Lime Butterfly(Papilio demoleus)

Males seem to benefit from the sodium uptake through mud-puddling behaviour with an increase in reproductive success. The collected sodium and amino acids are often transferred to the female with the spermatophore during mating as a nuptial gift. This nutrition also enhances the survival rate of the eggs.

Common Lime Butterfly(Papilio demoleus)

 Papilio demoleus is an aggressive and very common butterfly. It is perhaps the most widely distributed swallowtail in the world. The widespread range of Papilio demoleus indicates the butterfly's tolerance and adaptation to diverse habitats. It is to be found in savannahs, fallow lands, gardens, evergreen and semi-evergreen forests and shows a preference for stream and riverbeds.