JERUSALEM — For many Israelis, the biblical comparisons were irresistible: locusts were swarming across the border from Egypt three weeks before Passover, like a vivid enactment of the eighth plague visited upon the obdurate Pharaoh. Others with a more modern sensibility said it felt more like Hitchcock.

Israel first announced that it was on “locust alert” on Monday, after large swarms were spotted in the Cairo area. The Food and Agriculture Organization of the United Nations warned that wind and climate conditions increased the chances of an entomological cross-border invasion.

The Ministry of Agriculture set up a hot line for swarm sightings. By Tuesday, grasshoppers the size of small birds were reported on balconies and in gardens in central and northern Israel. But the largest concentration, an ominous black cloud of millions, settled for the night near the tiny rural village of Kmehin in Israel’s southern Negev desert, not far from the border with Egypt.

Potato farmers in the area complained that their fields were being ruined. Drivers said they could not see through their windshields for all the bugs flying in their direction.