More than 100 Hongkongers rolled out a different kind of welcome for mainland tourists in Tsim Sha Tsui last month. Outside luxury-goods stores along Canton Road, protestors hurled insults and obscenities at the visitors, and several stores rolled down their shutters for fear that the crowd would run amok. Mock cans of DDT pesticide were reportedly aimed at the mainlanders during what was billed as an "anti-locust" protest.

For a nation so dependent on agriculture, imperial China was surprisingly ignorant about locusts. As late as the Song dynasty (960-1279), it was widely believed that locusts were mutant forms of fish and shrimp. "During droughts when the rivers dry up," it was written, "the eggs of fish and shrimp would hatch into locusts. Therefore, an abundance of fish is a harbinger of a good harvest year."

Methods of eradicating the scourge included banging on gongs, burning and trapping locusts at dawn when their wings were wet and then killing them. It wasn't until relatively late in imperial China that Ming-dynasty Renaissance man Xu Guangqi (1562-1633) conducted a study of 111 recorded plagues over the previous two millennia. His conclusion was that the peak period for locusts was "between summer and autumn, when the hundred crops have matured and are ripening, resulting in the most extensive damage".