The house-dust mite, D. pteronyssinus (Trouessart) was reared in the laboratory at 25 +/- 1-degrees-C, 75 +/- 5 % R.H, and complete darkness on both media wheat bran and wheat bran with yeast powder. Biological aspects have been obtained on two diet for the four generations, complete development from egg to adult averaged 24.6 +/- 0.3 and 18.4 +/- 0.3 days for females and males on wheat bran and 37.6 +/- 0.3 and 24.1 +/- 0.4 days for females and males on wheat bran with yeast powder. Egg incubation period, larval, protonymphal and tritonymphal durations were studied. Hatching, mating and oviposition were investigated. The hypopus did not occur, no parthenogenesis was observed.