In a seminal paper on the biology and pathology of "Tunga penetrans", Eisele "et al." (2003) provided and detailed the five stages of tungiasis, thereby detailing the "in vivo" development of the female chigoe flea for the first time. In dividing the natural history of the disease, the Fortaleza Classification formally describes the last part of the female flea's life cycle where it burrows into its host's skin, expels eggs, and dies. Due to the nature of the discussion, overlap with other sections, particularly the one on symptoms, is unavoidable.