Table 1 Comparison between stable carbon isotope analysis and conventional approaches applied in studying the development of Cordyceps sinensis.

Duration for different stages⁴⁰

Around 2 months

About 3–5 days

3–4 months

Around 2 months

Stable carbon isotope analysis (δ¹³C values of subsamples*)

H1 to H2: highest value, initial infection

A3 to Ai: slightly declined

H1 to S1: sharply jumped down

S1-Si: continuously decreased

H2 to T3: slightly declined, inception

T3 to A3: sharply decreased, incubation

Field observation in morphology

Could not be observed due to no symptom)⁴⁰

The larva started to behave abnormally, and its skin colour gradually changed^31,40.

Relatively long dormant period^40,43 (“Winter-worm”)

The stroma started to germinate at the head for more than 2 months and eventually formed the mature stroma^31,41,43 (“Summer grass”).

Macroscopic observation in the growth of mycelia

The inside became hollow and the integument became moist. Then, a white hyphal coil firstly developed at the pharynx and gradually extended to the whole body⁴².

The stiff worm was gradually coated by mycelia³¹.

1^st: The stroma kept growth for one month to reach the length of around 3 cm. Then, its apex swelled and covered with the granulated perithecium.

2^nd: The stroma continued to grow for 20 days to reach the final length of about 4.5 cm.

3^rd: In the coming 10 days, the stroma would underwent the development period of ascospores, including growth, maturation, and eruption^31,41.

Microscopic observation in the growth of mycelia

1^st: The infectious fungus firstly invaded the host and formed several spheroid hyphal bodies.

The inner of a stroma was made up of interwoven mycelia, and finally multiseptate and elongate fusoid ascospores were produced³¹.

2^nd: The hyphal bodies multiplied in the host and gradually formed multinucleate hyphal bodies.

3^rd: The multinucleate hyphal bodies further developed into mycelia through the following processes: budding multiplication, conglobation and connection, and hyphal body fusion. The mycelia continued to grow and completely filled the host body cavity^15,16,31,41.