Unlike most cestodes, this one is only three segments long. The hindmost segment is gravid, with numerous ova. The definitive hosts for these tapeworms are dogs. Scolex of a tapeworm showing suckers, a prominent rostellum and at least 14 spines. Ovum of Hymenolepis diminuta , the rat tapeworm.
Insects ingest the ova, and the cysticercoid larvae develop in the hemocoel.
Rats acquire the infection by ingesting the insects. Occasionally, humans are reported infected with the rat tapeworm.