The plague of locusts that hit Hohhot last week had trickled down to only a handful yesterday, said agricultural officials in the capital of North China's Inner Mongolia Autonomous Region.

The brown insects, whose scientific name is Oedaleus asiaticus, have been puzzling technicians, as many experts had previously believed that this type of locust could not migrate a long distance.

Chen Jing, director of the city's plant protection station, said: "The number of locusts peaked on Wednesday and Thursday in downtown, as they reached up to 200 per square meter in some areas."

The insects covered trees, walls and windows in some quarters of the city, gnawing at leaves, grass and anything they could eat, she said. The problem was especially acute in brightly lit areas because the locusts are photokinetic - they move in response to light.

But the creatures seem not to have caused any substantial damage to the city, Chen said.

"They have either died or flown away and, by today, there were only sporadic plagues of locusts in the city center," she said.

Some local people claimed that the insects were attracted by Hohhot's strong night-time lights and flew to the city from nearby prairies, but Chen said she personally doubted this theory.

"It is common knowledge that this type of locust is unable to travel long distances," she said. "Besides, the prairies and farmland nearby did not have such massive numbers of locusts recently as, in many areas, the density was four to 20 locusts per square meter.”

Zhang Zuoran, of the Inner Mongolia Autonomous Region Grassland Plant Protection Station, said the unprecedented numbers of locusts in Hohhot may prompt a revision of people's traditional views of the insect.

"Many people have taken it for granted that these locusts could not migrate for long distances," he said. "But our on-the-spot investigation indicated they can fly a fairly long distance if powered by the wind." Usually, this type of brown locust can fly only up to 120 meters away from its normal habitat, Zhang said.

But, on July 19, Zhang and his colleagues observed in a grassland area of Shiziwang League - 100 kilometers north of Hohhot - that the relatively strong winds had enabled the locusts to travel much longer distances.

(China Daily August 5, 2003)