Moths hitch a ride on jet streams to get to warmer climates

A new study has shown that migrating insects like moths can hitch a ride on favourable jet streams and adjust their flight direction to get to warmer climates.According to a report in Nature News, the study used radar to track the movement of more than 100,000 noctuid moths, hawkmoths and butterflies as they migrated to northern Europe in the spring and south to the Mediterranean in autumn every year between 2000 and 2007.Jason Chapman of Rothamsted Research, the agricultural research institute in Harpenden, UK, and his colleagues report that the insects can control the direction in which they fly, selecting the most favourable winds to maximize the distance they travel.The team also found that insects tend to fly higher up, where the wind is fastest.The silver Y noctuid moth, for example, flies 425 m above ground - higher than the top floor of the Empire State Building in New York. How the moths detect these altitudes is still being studied, but sophisticated mechanisms that determine wind speed while they are flying help them to reach average speeds of 54 km an hour. With an additional jet stream push from behind, they can achieve top speeds of up to 90 km an hour. The moths seem to be able to detect the wind's direction and, using some sort of internal compass, correct their flight path. These moths only take flight when winds are at least somewhat favourable - never flying across the wind or into it. If winds don't completely align towards their destination, migrants can partially correct for that drift, keeping themselves on their preferred trajectory rather than simply being propelled downwind. In spring, migration corresponded with the northward wind. But in the autumn, migrants still arrived south even though the prevailing wind tended to blow eastward.It is well known that migratory birds are able to control their flight direction, sometimes flying across the wind. But because insects have a shorter lifespan than birds, they can't afford to waste time getting to their breeding grounds."Because insects fly slower than birds, they had to evolve a way to increase their speed. The way they've done this is to really exploit the wind," said Chapman. "Insect migration was always thought to be a rather chancy process," said Chapman. "We show evidence that a wide range of insects exert quite a lot of control on their pathway and are not, in fact, at the wind's mercy," he added.