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The
enormous number of migratory moths flying high above our heads throughout the night aren’t at the mercy of the winds, but use them to reach their destinations, according to a study.
While it isn’t yet clear exactly how they do it, researchers said the new findings offer the first hard evidence that nocturnally migrating insects have an inbuilt compass that helps guide them. Using entomological radar, the study estimated that in a one-month period, some 200 million Silver Y moths migrated southwards over Britain, travelling some 300 km per night at 50 km per hour. Findings of the study have been published in the online journal Current Biology. “There has been speculation for many years about whether insects relying on the wind for their migrations can have any control over the direction in which they migrate,” said Jason Chapman of Rothamsted Research, who conducted the study. “If they don’t have any control, in many years the majority of the autumn population would get blown in unsuitable directions and die — the so-called Pied Piper effect. “Our studies demonstrate that the moths can influence their direction and speed of movement in a number of ways.” Researchers found the moths migrate only on nights when the wind directions are favourable. They then select their flying altitude so as to stay within the fastest winds, thus maximising their speed. The new study is the first to show that insect migrants flying high in the air on dark nights also use this method to beneficially influence their flight direction. Considering the high pest status of many insect migrants, and the positive effects of global warming on the frequency of insect migration, their movements will have increasing impact on global agriculture. — IANS
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