[6] At the anterior end, a cone-shaped structure protrudes, supported by a palisade of stiff microtubular rods (nematodesmata).

[9] While D. nasutum is sometimes described as feeding exclusively upon Paramecium, it has been shown that the organism will readily devour other ciliate species, including Colpoda, Colpidium campylum, Tetrahymena pyriformis, Coleps hirtus, and Lacrymaria olor.

[1][10] Moreover, strains of Didinium raised on a Colpidium campylum will actually show a preference for a diet made up of that species, as well as a diminished ability to kill and ingest Paramecia.

[11] In the laboratory, other environmental stimuli, such as the age of the growth medium or the accumulation of certain metabolic waste products, can also trigger encystment.

[15] In 1859, Samuel Friedrich Stein moved the species to the newly created genus Didinium, which he placed within the order Peritricha, alongside other ciliates which have a ciliary fringe at the anterior of the cell, such as Vorticella and Cothurnia.

[17] In 1974, John O. Corliss created the order Haptorida, within the subclass Haptoria, for "rapacious carnivorous forms" such as Didinium, Dileptus, and Spathidium.