The genus was then used for members of the Entomophthorales known only (at the time of their collection and description) from their thick-walled resting spores.

[7] It was first thought in 1871, that the fungus was a conidial stage of Entomophthora muscae (a fungal parasite that attacks houseflies).

[9] Botanist I. Krassilstschik in Russia in 1886,[10] also discovered the fungus within the larval body of the coleopterous sugar-beet curculio Cleonus punctiventris.

Populations of both host species were also infected with the conidial state of a fungus identified as Entomophthora virescens.

It is possible that T. megaspermum and E. virescens represent the resting spore and conidial states, respectively, of a single fungus species, Entomophthora megasperma.