This investigation was conducted to study the different biological aspects of astigmatid mites, Tyrophagus putrescentiae (Schrank) and Rhizoglyphus robini Claparede (Astigmata:Acaridae) when fed on different food kinds  i.e. pure white wheat flour, normal wheat flour, wheat germ, rice flour, maize flour and semolina at 25+2 ºC and 75+5 % R.H.. The results indicated that there were obvious differences between (incubation period, life cycle, longevity and life span) of both T. putrescentiae and R. robini and the different introduced food. The longest life span periods of T. putrescentiae male and female were noticed when the individuals fed on wheat flour, as  recorded 41.61 and 50.9 days, respectively. However, the longest life span periods of R. robini were observed on maize flour and recorded 49.2 and 41.2 days for male and female indivduals, respectively. The food type's suitability clearly affected the number of deposited eggs by the adult female of both T. putrescentiae and R. robini and revealed highly significance between the feeding on wheat flour for the first mite and maize flour for the second one (the most suitable feeding sources for mites) than any other feeding types. The highest number of T. putrescentiae eggs was 40.2 eggs on wheat flour and the lowest number was recorded on wheat germ (27.8 eggs).However, the highest deposited number of R. robini eggs was noticed when adult female fed on maize flour (140.2 eggs), but the lowest number of laid eggs was found when the indivduals reared on wheat germ (70.4 eggs).