Nocturnally-flying moths can control the direction of their migrations

A recent research that took place at Rothamsted Research Station has permitted to better understand the complex mechanism of the moth flight during the migration period.

Till now researchers thought moths were carried by the wind from a location to another, without any control of their flight, but now we know they can control its direction and go to a more suitable place to permit them to complete their development and then to reproduce.
They can achieve their aim by means of a particular mechanism, similar to a compass, like that we can find in migratory birds and permitting them to control their flight direction and speed of movement in a number of ways.

The moths migrate only during those nights when the wind directions are favourable, that is when wind is blowing approximately southwards. Moths can also select their flight altitude so as to stay within the fastest winds and maximizing in this way their speed. During the flight they proceed in a roughly downwind direction, adding speed (of 5 m/s) to the wind one, so that they could move even quicker.
Most unexpectedly, said Chapman (from the Plant and Invertebrate Ecology Department, at Rothamsted Research Institute), the moths compensate when the wind direction is substantially off target.
This mechanism called 'partial compensation for wind drift' and it had been previously observed in insects, such as butterflies and social bees, that fly just a few feet above the ground during the day, added Dr. Chapman.

The new study is the first to show that insect migrants flying high in the air during dark nights also use this method to influence their flight direction.
Anyway we can tell the moths can influence their direction and speed of movement in a various number of ways.

Using entomological radar ('Vertical-Looking Radar'), the researchers estimated that in August 2003 about 200 million Silver Y moths migrated southwards over the U.K., traveling at more than 50 km per hour over distances in excess of 300 km per night. The researchers concluded saying: 'Considering the distances these moths would have flown, and their sophisticated orientation behaviors, it is apparent that many will have reached their over-wintering regions in just a few nights'.

The researchers think also that all these mechanisms may prove to be widespread among more migratory insects and considering that lot of them are dangerous to crops and as well the positive effects of global warming on the frequency of insect migration, the long-range movements of such pests will have increasing impacts on global agriculture. In this direction could be important to understand and predict their spatial dynamics.

The researchers involved in this study are:

To learn more about this argument you can read the article, published on 'Current Biology', nr. 18, 1-5.

Source: Rothamsted Research Station - UK

Author: , May 29, 2008

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