In the present study, the role of earthworm species Drawida willsi Michalsen in cellulose decomposition of microbial rich pressmud substrate has been evaluated, and to assess whether this native species of earthworm digest cellulose directly (with associated gut microbiota) and also to know if there is any effect on microbial biomass and activity leading to a change in the equilibrium between fungi and bacteria during decomposition process. The findings suggest that the presence or absence of earthworms in vermireactors significantly increased the rate of cellulose decomposition (0.43 and 0.26% cellulose loss day(-1) with and without earthworms, respectively). However, the direct contribution of D. willsi to degradation of cellulose was not significant; although the presence of earthworms considerably increased microbial biomass and cellulase and beta-glucosidase activity. (C) 2010 Elsevier Ltd. All rights reserved.