Most are aggressive predators equipped with long, mobile proboscides lined with toxic extrusomes, with which they stun smaller organisms before consuming them.

[2] Dileptus species have served as model organisms used in the study of ciliary patterns, ontogenesis, conjugation and food acquisition.

[3] Dileptus bodies are typically narrow or cylindrical, and have a macronucleus made up of more than a hundred scattered nodules.

Most Dileptus are colourless, but two nominal species carry symbiotic green algae in their cytoplasm.

[2][3][5] In a comprehensive taxonomic study published in 2012, Peter Vďačný and Wilhelm Foissner restricted the genus Dileptus to dileptids "having more than 50 dispersed macronuclear nodules that divide individually," which left only ten nominal species within the group.