The effect in the production of fly larvae using four substrates: wheat bran, corn germ, filter cake and rice bran adding 20% of pig manure was evaluated. Insects cages were used to raise the house flies, under a randomized block design with four replicates. The temperature inside the substrates and outside was measured. In each treatment the number of larvae obtained and the average weight of these were determined, calculating the corresponding yields. The weight and crude protein content of the substrates were determined, at the beginning and end of the experiment, as well as the presence of Salmonella spp. and faecal coliforms. The comparisons of the temperatures, and the variables corresponding to the larvae were made by means of simple Anova, and for the protein contents of the substrates tests of related samples were used (P < 0.05). The temperature within wheat bran was higher than the rest of the substrates (P < 0.05) from the third to the fifth day. The weight of the larvae of flies did not differ by substrates (0.016899 g to 0.018160 g). This last substrate was also the one that showed a higher yield of fly larvae (82.37 g/kg). There is a decrease in crude protein in bio transformed substrates. No presence of Salmonella spp. was detected in the substrates, but faecal coliforms were detected in the sow.