The white-spotted flower chafer, Protaetia brevitarsis (Coleoptera: Cetoniidae), has been registered as a kind of human food in Korea in December, 2016. The larva has been known to have an important source for medicinal properties such as anti-cancer activity and prevention of liver-related diseases. However, the consumer market is depressed because of high price of the larvae produced. To promote consumption on the larvae, the production expense should be reduced. This study was carried out to evaluate two kinds of agricultural by-products as food source of P. brevitarsis larvae to improve the productivity and to reduce production costs of the larvae. The larvae were fed with spent king oyster mushroom (Pleurotus eryngii) substrate (P-SMS) and spent shiitake mushroom (Lentinula edodes) substrate (L-SMS), with a control of fermented oak sawdust. The effect of the diets on the development of P. brevitarsis, contents of minor nutrient components and heavy metals in the larvae produced were examined. In P-SMS diet, the larval rearing period was shortest as 16.2 days, the increasing rate of larval weight and the cocoon weight were highest as 156.3% and 4.1 g, respectively. Pupation rate was 100% and the adult emergence was highest as 93.3% in P-SMS d
iet, with no difference with control diet. Total nitrogen content reared in the P-SMS diet was highest as 10.28%, and the minor component, particularly Fe, was higher as 145.8 mg/kg than other diets. The heavy metal content in the larvae was below the minimum residual levels of Ministry of Food and Drug Safety of Korea. The oviposition preference of adults showed no significant difference among the diets. It was estimated that P-SMS has about 667,960 Won in economic gains per 100 kg larvae compared to FOS.