Three new species of Harpellales, collected on Mt. Tsukuba, Kanto Plain on Honshu Island, are described. Stachylina philoricola, derived from midgut of Philorus sp. (Blephariceridae: Diptera), and Lancisporomyces tsukubaensis, derived from the hindgut of Amphinemura sp. (Nemouridae: Plecoptera) nymphs, are described. Blephariceridae is newly added to the host insect families of Harpellales. A new genus, Zygopolaropsis, is proposed to accommodate the new species Z. sphaerica, derived from the hindgut of Baetis thermicus (Baetidae, Ephemeroptera) nymphs.