Winter worm, summer grass
High in the alpine meadows of the Tibetan Plateau, between 3,000 and 5,000 meters, a strange biological drama unfolds underground. It involves a parasitic fungus, Ophiocordyceps sinensis, and the larvae of ghost moths from the genus Thitarodes. The life cycle begins when fungal spores infect a moth larva living underground, where it feeds on plant roots. The fungus germinates inside the living host, slowly replacing the larva's tissue with its own mycelium. This process kills and mummifies the larva, leaving its exoskeleton intact. After overwintering, a dark, stalk-like fruiting body, or stroma, erupts from the dead larva's head and pushes up through the soil. This entire fungus-larva combination is known in Tibetan as yartsa gunbu, which translates to "winter worm, summer grass," and has been used in traditional medicine for centuries.
The fungus contains several bioactive compounds, including cordycepin, adenosine, and various polysaccharides. Traditional Chinese Medicine, where it was first recorded in the 18th century, values it as a tonic believed to treat a range of ailments from fatigue to respiratory problems. Its reputation grew internationally after 1993, when Chinese athletes, who reportedly used it in their diet, broke several world records in track and field. The fungus's high value is also tied to its use as a status symbol.