**2. Mass Production of** *Cordyceps* **Fungi**

Ascomycete entomopathogenic fungi are facultative with saprophytic growth abilities. However, it is still technically challenging, often difficult, to induce fungal sexual fruiting bodies on artificial media or on insect hosts under laboratory conditions [26]. Until recently, induction of the fruiting-body formation of the caterpillar fungus *O. sinensis* (best known as *C. sinensis*, one of the most expensive traditional medicines) was not successful [27,28]. After inoculation of the ghost moth (*Hepialus* spp.) larvae, it is an energy-intensive process for fungal infection and development within the insect body cavity at a relatively low temperature (less than 18 ◦C) and the formation of fruiting bodies for a total period of more than half a year (Figure 1A). Dozens of tons of the fruiting bodies (attached with insect cadavers) can now be produced annually in China [28]. In contrast, mass production of *C. militaris* has long been successful by inoculation of fungal propagates on artificial media (e.g., rice medium) (Figure 1B). Different from the homothallic nature of *O. sinensis* [26], *C. militaris* is sexually heterothallic but its single mating-type can also fruit but without mating and meiosis to produce sexual perithecia [29]. Without considering the mass production of *C. militaris* in Japan, South Korea and Vietnam, the annual yield of the dried fruiting bodies reaches up to 10,000 tons per year in China [22]. The fruiting bodies of *C. cicadae* together with the mycosed cicada pupae have also been used as a TCM in renal protection or for the treatment of chronic kidney disease [23]. Mass production of this fungus has also been successful with a yield of hundreds of tons each year (Figure 1C). In contrast to *C. militaris*, asexual fruiting bodies, i.e., synnema-like structures, are largely produced by *C. cicadae* [23]. A few other species such as *C. guangdongensis* have also been mass produced at different magnitudes in Asian countries. Without consideration of the liquid fermentations of *Cordyceps* fungi [22], careful evaluation and safety assessment are still required regarding the (daily) consumption of enormous amounts of fruiting bodies and their related products as foods or health-promoting additives, and utilization of the leftover substrates as animal feed.

**Figure 1.** Mass production of *Cordyceps* fungi. (**A**) Successful induction of the fruiting bodies (arrowed) of *O. sinensis* after inoculation of the ghost moth larvae for more than 150 days (image taken from the Sunshine Lake LLC, Yichang, China). Bar, 1 cm. (**B**) Mass production of *C. militaris* in plastic bottles (image taken from the Honghao Biotech Company, Jiangmeng, China). Insert, the fruiting bodies formed in a bottle 45 days post-inoculation. Bar, 1 cm. (**C**) Mass production of *C. cicadae* in plastic boxes (image taken from the BioAisa Pharmaceuticals, Pinghu, China). Insert, the fruiting bodies formed in a box 20 days post-inoculation. Bar, 1 cm.
