Why Do Locusts Swarm and How Long Does It Last?
Certain conditions favor the creation of locust swarms: unusually heavy desert rains, favorable winds, good crops after periods of drought, a ban on long lasting pesticides and civil strife that disrupts control efforts. Rains foster egg development and promote quick growth of plants the locusts feed on. When otherwise harmless juvenile locusts get too crowded, they will suddenly align themselves and march in the same direction, triggering a potentially devastating swarm.
Locust swarms have no particular course of action and no idea of where they want to go. They are transported primarily by the winds and whether the end up in a field or barren patch of desert or even the sea is primarily a matter of luck. Ideally they hope to ride a wind to a place where winds converge and produce rain.
Locust can stay aloft for 17 hours at a time, and if the winds are strong enough they can range 3,000 miles in their lifetime.
Swarms can remain active over a long period in a large area. In 1985 and 1986, locusts began breeding around the Red Sea. They moved into Sudan in the summer of 1986. Civil war there hampered control efforts and they invaded North Africa and Arabia in the summer of 1987. Good rains in those areas allowed more breeding than usual.
Until recently, little was known about why solitary grasshoppers change their behaviour when in company – grouping together to indulge in widespread mayhem. Scientists have discovered a link to a neurochemical called serotonin, found in the brains of many animals including humans.
A study by the universities of Oxford, Cambridge and Sydney has found a build-up of serotonin in the nerves of the middle part of the locust’s body controlling its legs and wings causes, within the space of a couple of hours, the solitary locust to turn into its swarming alter-ego.
The finding opens the possibility of stopping the process long before it happens, by blocking the action of serotonin. The research team says that this discovery has great importance for it could finally lead to the production of insecticides capable of stopping vast swarms of locusts.
This could be used to prevent the massive destruction of crops that occurs when locusts swarm – a threat affecting the livelihoods of one-tenth of the world’s population. Globally there are about a dozen species of swarm-forming locust in a belt covering some 20 per cent of the world’s landmass, from north Africa to China.