Hymenolepis microstoma has a cosmopolitan (world-wide) distribution.
Hymenolepis microstoma is an enteric, obligate parasite. Adults live in the bile duct and small intestine of rodents such as mice (Mus musculus), and larvae infect grain beetles such as Tribolium spp., in which they metamorphose from larvae into juvenile worms.
Adults absorb nutrients directly from the host gut. They have lost their mouth and intestine and instead use their tegument to do the job of the intestine.