Tamil Nadu has witnessed large-scale migration of butterflies belonging to the Danainae sub-family from the Eastern Ghats and plains towards the Western Ghats during September.
They migrate from the Eastern Ghats and plains towards various nearest hill ranges of the Western Ghats before the start of northeast monsoon.
During April and May, these butterflies, generally called ‘tigers and crows’ migrate from the Western Ghat hill ranges towards the Eastern Ghats and plains of Tamil Nadu.
This is happened before the onset of the southwest monsoon.