I found the following info online:
Cricket Culture in China encompasses a 2000 year history of both singing insects and fighting crickets. Under the Song dynasty (960 - 1279 A.D.), cricket fighting flourished as a popular sport. Such activity was still flourishing during the Qing Dynasty (1616-1911), when the Emperor's family, city residents or village men and scholars, all collected crickets feverishly every summer.
A big body, big jaws and a black face are the standard of excellence for a cricket. But to find a good one is not easy. Fu Cun, who has 20 years experience of cricket fighting, said when he went out to catch crickets he often waited in the field a whole day for the right one. The way a cricket is raised is also crucial. "I feed my crickets a special food combining corn flour, wheat flour and apple pieces," said Huang Huoyong, a stall keeper at the Xizang Nanlu Flower and Bird Market. For especially excellent crickets, calcium tablets or ginseng might be added to strengthen their bodies and hone their fighting abilities. Huang said in the current cycle of cricket fighting, it is quite common to hear such stories: for some men, the adored creature who shares their bed each night is their champion cricket rather than their wife.
You can find more info at China Culture.org.