Myiasis is an infestation of the skin by developing larvae(maggots) of a variety of fly species within the arthropod order Diptera. In cutaneous myiasis, the 2 main clinical types are wound myiasis and furuncular myiasis. In nasopharyngeal myiasis, the nose, sinuses, and pharynx are involved. Ophthalmomyiasis affects the eyes, orbits, and periorbital tissue, and intestinal and urogenital myiasis involves invasion of the alimentary tract or urogenital system.
Once deposited in the skin, the larvae start out as small and fusiform and later become pyriform to ovoid as they reach full development at lengths of 15-20 mm. They are encircled by several rings of spines. Eventually, if the cycle is unperturbed, larvae emerge from the host in 6-7 weeks and drop to the ground, where they pupate to form flies in 2-3 weeks.
Info from here