Caterpillar fungus or yarsagumba, is known in China by the Tibetan term, yartsa gunbu, which means "winter worm, summer grass." It's one of the most highly valued medical materials in traditional Chinese medicine, along with ginseng & pilos antler.
In Yunnan caterpillar fungus grows wild in the mountains. Every spring there is a 40-day season when it can be found on the slopes. Many of the locals go out during the season to collect caterpillar fungus and some of them sell it in the cities