The death of the flea marks the beginning of substage 4b (around day 25 post-penetration) as the body begins to eliminate the parasite through skin repair mechanisms (e.g. shedding and subsequent skin repair). At this phase, the lesion is seen as brown or black.By the 5th stage of tungiasis, the carcass of the T. penetrans flea has been expelled and there are circular skin residues of the infection that remain. There are only lingering symptoms at this time, described in the next section. Morphology
In a study of 1000 freshly ejected T. penetrans eggs, it was found that females are generally smaller than males for all criteria. In some cases, though, females had a bigger epipharynx and maxillar palpus. Due to its burrowing activity, the chigoe flea has developed a well-developed lacinia and epipharynx that is used to penetrate the skin. Overall, the fleas’ head is relatively flattened, which again aids in burrowing through the epidermal and dermal layers.Investigators have also found that adult T. penetrans have different morphologies with respect to the shape of their head. Some have a rounded head, others have head shapes that resemble ski ramps more than anything else; still, others demonstrate head shapes that are very linear with a slight bulge at the nose. These morphologies were seen to be host-specific, as only fleas of some head-types were found in specific hosts.
Tungiasis  is an inflammatory skin disease caused by infection with the female ectoparasitic Tunga penetrans, a flea also known as the chigoe, chigo, chigoe flea, chigo flea, jigger, nigua, sand flea, or burrowing flea (and not to be confused with the chigger, a different arthropod). The flea and the disease that it causes are found in the tropical parts of Africa, the Caribbean, Central and South America, and India. Tunga penetrans is the smallest known flea, measuring 1 mm across. It is also known in Latin America as the nigua and bicho de pie (Spanish) or bicho de pé (Portuguese), literally "foot bug". Tunga penetrans is a member of the genus Tunga, which comprises 13 species.Tungiasis causes skin inflammation, severe pain, itching, and a lesion at the site of infection that is characterized by a black dot at the center of a swollen red lesion, surrounded by what looks like a white halo. Desquamation of the skin is always seen, especially after the flea expands during hypertrophy. As of 2009, tungiasis is present worldwide in 88 countries with varying degrees of incidence. This disease is of special public health concern in highly endemic areas such as Nigeria, Trinidad and Tobago, and Brazil, where its prevalence, especially in poor communities, has been known to approach 50%.The chigoe flea is properly classified as a member of the order Siphonaptera as it is a flea. Although commonly referred to as chiggers, true chiggers are mites, which are minute arachnids.