BEIJING - Although classified as a mushroom, caterpillar fungus - or dongchongxiacao, which literally means "winter insect, summer grass" - is a parasite that attacks moth larvae. It slowly grows inside them until it kills and mummifies them, eventually producing a fruiting body that releases spores that infect other caterpillars. The fungus is harvested in May and early June, just before the spores are released. If consumed, it is said to boost stamina and sexual performance, as well as strengthening the immune system, lungs and kidneys. It is most commonly ground into a powder, dissolved with boiling water and served like tea.

Caterpillar fungus only grows at high altitudes on the Tibetan plateau in an area that stretches from Nepal, through northern Sichuan province and into Qinghai province. However, warming temperatures and over-harvesting have caused populations to fall by nearly 90 percent in some areas, say experts.

As a result, it is one of the most valuable medicinal products on the market today.