In a rare phenomenon, Tamil Nadu witnessed a large-scale movement of Lime butterflies (Papilio demoleus) at May-end and June this year.
Observers spotted Lime butterflies moving from the north to the south and in the southwestern direction at a rate of 10 species per minute from June 9 to 14 and again from June 17 to 19. Another mass movement was observed on June 24. The northern and western parts of Tamil Nadu witnessed the highest of the movement.
The period is normally marked by the mass migration of milkweed family butterflies Dark blue tiger, Blue tiger, Common crow and the Double-branded crow (commonly known as ‘crows and tigers’) from the hill ranges of the Western Ghats to the plains and to the Eastern Ghats, triggered by the southwest monsoon. The movement of crows and tigers was limited to the Western Ghats foothills this year.
“Lime butterfly is not known to migrate or disperse regularly, but they are known to emerge in large numbers (population outburst) once in a few years and disperse to short distances along the ghats. Such a scenario was last observed during May 2018, when a large-scale movement was observed along the paths of the Bhavani and the Kallar near Mettupalayam, peaking to 200 specimens per minute,” said A. Pavendhan of The Nature and Butterfly Society (TNBS).
Tamil Nadu received widespread rain from April to June this year, and this could be one reason for this phenomenon, according to the seasoned observers of the TNBS.
According to them, the movement of the species belonging to the Swallowtail family was seen over Erode and Tiruppur into the direction of the Western Ghats bordering Coimbatore district and adjacent districts, including the Kotagiri side of the Nilgiris. Coimbatore city, too, witnessed a high presence of Lime butterflies, and they were observed laying eggs on all possible lime plants, their larval host plants.
Mr. Pavendhan observed the movement of the species while travelling to the northern parts of Tamil Nadu, including Chennai.
“The northern parts of Tiruppur district witnessed a continuous movement of Lime butterflies in large numbers for a week. The movement was also high along the highway between Coimbatore and Tiruppur districts, and the count went up to 20- 25 specimens per minute,” said TNBS member S. Gopal Krishnan of Tiruppur.
Dark Blue Tiger (Tirumala septentrionis), Crow (Euploea) species and Emigrants (Catopsilia pomona) were the other species which were observed moving along with Lime butterflies in small numbers.
TNBS members K. Sadhees Kumar in Erode, C.V. Nishanth in Coimbatore and H. Ramanasaran in the Nilgiris documented the phenomenon in their districts along with other enthusiasts. The movement observed by the TNBS in Tamil Nadu was shared with the now well-established migration monitoring WhatsApp group, Butterfly Migration India, which is collecting data from observers across the country.
