Studying life cycle of butterflies

We discussed the studies conducted by cubists on butterflies, @Anupmourya shared he started the work on slugs but also saw butterflies so he started to work on butterflies. He said he saw butterflies mating, he later found out that butterflies eggs can be seen on curry plant leaves as caterpillars feed on curry leaves. He found curry plant and found eggs of butteflies on it. He observed the entire lifecycle from egg to larvae to pupae and butterfly emerging from it. Cubists are making hypothesis when the egg will hatch to form the caterpillar, One observation suggests larvae emerged from eggs after two days of observation.
But how do we know when were eggs laid?

The matting butterflies found by Anup

Picture of Anup’s Butterfly hatched from eggs.

While discussing about mimics, Anup also shared photos of Red rose butterfly and Common mormon butterfly. Red rose is mimic of Common mormon.

Common mormon has more colors than Red rose so Red rose mimics gets saved from predators.