Abstract: In many areas in China, Chrysomya megacephala F. has gradually invaded the ecological niches occupied by Musca domestica L. and become the dominant species at garbage sites in the urban areas. To explore the influence of foods on the development of M. domestica and C. megacephala larvae when they were reared solely or jointly, the oviposition preference and life history of the F1 generation of wild blowfly C. megacephala and housefly M. domestica on wet wheat bran, pork muscle and their mixture were observed in the laboratory. The results showed that: (1) Blowflies preferred to lay their eggs on substrates containing pork muscle while houseflies preferred to lay their eggs on substrates containing wheat bran. (2) Newly-hatched housefly and blowfly larvae could reach adulthood on diets containing pork muscle. When raised on wheat bran, newly-hatched housefly larvae could reach adulthood while newly-hatched and 2nd instar blowfly larvae all died before entering into the next instar, but some 3rd instar blowfly larvae could reach adulthood. (3) When the same number of newly-hatched housefly and blowfly larvae grew mixedly on diets containing pork muscle, blowflies exhibited shorter developmental duration and higher survival rate than houseflies. When reared mixedly with houseflies on wheat bran, blowflies showed shorter developmental duration and higher survival rate than the same instar blowflies that grew solely on wheat bran. These results suggest that in coexistence the housefly can promote the utilization of the vegetable resource by the blowfly. This might be one of important reasons why the blowfly can invade successfully the ecological niches occupied dominantly by the housefly.

Key words: Chrysomya megacephala, Musca domestica, nutrition utilization, oviposition preference, growth and development, interspecific competition