Blue in colour, these worms migrate to the uplands in the spring and move back to the warmer, lower altitudes before winter sets in. For villagers of the areas they inhabit, the movement of these blue worms acts as a kind of weather forecast mechanism, implying that it will rain.
The Wah Umstew river joins the Wah Umsong to flow as a tributary of the Wah Umngot in the valley between certain areas of the Mawkynrew and Pynursla blocks. The worms inhabit the river beds of the Mawlyngot, Rasong and Rangphlang villages, especially during the winter.
Additional chief secretary P Barkos Warjri said as he was determined to see this phenomenon, he went to the Wah Umstew on April 15 through the Mawlyngot village where he saw several clumps of these worms.
"Thousands of them were piled up in two clumps on the river bed. The young ones are red in colour, but the mature ones, some of which grow up to one foot in length, are a rich blue," he said, adding that the next day, on April 16, it rained heavily and the villagers told him that the worms had started ascending the hills.
Birds and fishes usually have a sumptuous feast of these worms during migration, Warjri said. "The ones that survive multiply in the fields on the hills and fertilize the soil, returning as an army in October towards warmer areas and settling on river beds in the winter," Warjri said.
People avoid venturing into the fields in October as the surface is very slippery as these worms migrate in hordes during this season.