The caterpillar that is prone to infection by the fungus lives underground in the alpine grass and shrub regions of the Tibetan Plateau and the Himalayas, at an altitude between 13,000 – 14,500 feet. The dark brown to black fruiting body (or mushroom) emerges from the ground in spring or early summer, always growing out of the forehead of the caterpillar. The long, usually columnar fruiting body reaches about 12 inches above the ground.

Because the amount of Cordyceps is limited, and because of its value (about 1/8 the price of gold), over-harvesting and habitat destruction have become issues in Tibet, Nepal, Southwest China, and Mongolia. The fungus is being cultivated, but the wild-harvested product is in most demand. The fungus is found in very poor regions of the world and thus the search for this expensive product has caused large-scale economic and social dilemmas. The problems are varied in nature and include: 1) exploitation due to demand leads to species decline, 2) counterfeit and adulterated products are being sold, 3) harvesters sometimes insert a lead wire into the caterpillar body to make it heavier and therefore worth more, causing lead contamination, and 4) it is inadvertently causing a serious threat to the remaining tigers left in India because the wealth that cordyceps has brought to some Tibetan people is being used to purchase the hides of tigers and leopards for expensive and prestigious traditional costumes.

For medicinal use, good quality cordyceps should be large unbroken caterpillar bodies that are yellowish brown in color with a white, solid cross-section. Care should be taken to test the product to assure there is no sign of lead contamination.

Cordyceps sinensis is an insect parasitizing fungus found at high altitudes on the Qinghai-Tibetan plateau. This fungus lives primarily in the larvae of one particular species of moth, the Hepialus armoricanus, or Himalayan bat moth.

Fungal spores invade the caterpillar through its breathing pores, or are ingested by the caterpillar. The spores then germinate and penetrate the larva, entering its circulatory system, growing and eventually killing the host. Cordyceps is, in essence, the mummified caterpillar with fungus sprouting from it.

The name in Chinese “dong chong xia cao” (冬虫夏草) translates as “winter worm, summer grass” (meaning “worm in the winter, (turns to) plant in the summer”). The fungus infests the worm and lives on it in the winter, then in the transition from spring to summer, it metamorphoses into fungal mycelium (like a plant, or “grass”).

There are many other species of the genus Cordyceps, which all seem to have potent biologically active compounds present. There has been a great deal of attention and research given to Cordyceps and the genus has been shown to produce some potent antibiotics, immune stimulants, and anti-neoplastic agents.