Yarsagumba is the result of a bizarre parasitic relationship between fungus and insect. Spores of the Cordyceps mushroom invade and consume the larvae of the Himalayan bat moth, which live underground at altitudes of 10,000 to 16,000 feet for as long as five years, feeding on roots before they commence their metamorphosis into moths.
After the fungal spores have killed and mummified the larvae, they send up a spindly brown stem, a tiny knob-headed mushroom – and then they are very likely to be picked.
There have been many attempts to farm yarsagumba, but none has ever succeeded. The only way the precious fungus can grow is by the fortuitous concurrence of spore and larva in alpine atmospheric conditions – and brave collectors must be willing to risk their lives to collect it.