The potential use of Californian red earthworm flour as a nitrogen source for the production of lactic biomass was assessed. Three fermentation substrates, earthworm flour (EF), earthworm flour + yeast extract (EF + YE) and a commercial substrate MRS (control) were used. The substrates were formulated using 60 g L-1 of glucose as the carbon source and 34 gL-1 of earthworm flour as the nitrogen source.Weissella confusa was used as lactic acid bacterium. Nine batch fermentations were performed at 32°C and 100 rpm for 4 h, and the kinetics of the biomass concentration, lactic acid concentration and substrate consumption were compared. No differences were observed in the biomass concentration of the EF and EF + YE substrates, and final concentrations of 1.36 and 1.47 g L-1 were obtained, respectively. The lactic acid concentration did not differ significantly between EF + YE and the commercial substrate, and values of 4.79 and 4.33 g L-1 were obtained, respectively. These results suggest that earthworm flour can be a low-cost alternative for lactic acid biomass production.   Key words: Earthworm flour, Weissella confusa, lactic acid bacteria.