Trans-continental migration of dragonfly Pantala Flavescens between India and Africa: Energetics and Role of wind

The dragonfly species \textit{Pantala flavescens }migrates between India and Africa, covering a distance of around 14000-18000 km, crossing the Indian ocean twice, which is very extraordinary for a dragonfly or any flier. The route followed in this migration is India-Maldives-Seychelles-Africa-India, comprising of four legs. For such a migration, flight energetics and role of wind are most important factors. Computation models were developed for energetics, optimal time and route estimation. Energetics estimation shows, a P.flavescens can fly for 90hrs, covering a distance of 1400km; Without wind, time required for the completion of migration is more than 90hrs for all the legs. Our results show that with wind assistance, the time taken is well within 90hrs for all the legs. Also, P. flavescens detour from the virtual direct line connecting the two points of a leg in the sense of geodesic, and it follows the wind, which is expected based on the wind compensation capability of dragonflies. The results clearly show that wind assistance is vital if P.flavescens has to complete the migration. Pantala flavescens is able to achieve this great feat with the help of winds and stand in league of birds as far as migration flight is concerned.