Blue Mormon butterfly (Papilio polymnestor) belongs to the group of Swallowtail butterflies and is endemic to South India and Sri Lanka. They are fairly large and seen throughout the year.
I have seen the butterfly attracted to Ixora and Pagoda flowers in my garden for feeding, as is evident in these pictures. Hibiscus and Jasmine also are preferred food source. But the host plant for the larvae is Citrus plant.
The life cycle is similar to other swallowtails, with the caterpillar passing through five instars before the metamorphosis. If interested, you can view my posts on Common Mormon and Lime butterfly to see some stages of life cycle.
Blue Mormon is the State butterfly of the Indian state of Maharashtra.