The Insect That Crosses an Ocean Without Any Individual Making the Trip

The wandering glider is the most widely distributed dragonfly on the planet, found on every continent except Antarctica, and it got there by treating the atmosphere as a conveyor belt.

Populations move with the Intertropical Convergence Zone, the band of rain that sweeps north and south each year. Gliders ride high-altitude winds behind the rain front, breeding in the temporary pools it leaves behind. A pool that will be gone in six weeks is perfectly adequate for a species whose larvae can develop in about five.

The best-documented leg runs between India, the Maldives and East Africa, a crossing of well over 3,000 kilometres of open ocean, with the full multi-generational circuit estimated at 14,000 to 18,000 kilometres. Genetic work backs up the flight data: gliders sampled in Texas, India, Japan and South America are far more closely related than geography suggests, which only happens if they are all part of one enormous mixing population.

Green darners do a smaller, tidier version of the same relay in North America. Isotope work on wing tissue shows a spring generation flying north, a summer generation born there, and a third generation heading south — with no individual ever repeating its parents' route.

They are not navigating from memory. They are inheriting a route.