The larvae of Dermatobia hominis, (the human bot fly), are obligate ectoparasites that cause furuncular myiasis. The larvae feed inside of a subdermal cavity for 5 to 10 weeks, while undergoing development through 1st, 2nd and 3rd instar stages. When they are finally mature, they burrow out of the skin and drop to the ground to pupate in the environment. Larvae removed from humans may be in early or later stages of development and measure 2.5 to 7.0 cm in length. They have a piriform shape with concentric rows of black spines on all but the poster 3 body segments, anterior hook-like mouth parts and posterior respiratory spiracles. Like other myiasis-causing fly larvae, they can be differentiated by the morphologic features of their posterior spiracles. A pictorial key for identifying myiasis-causing fly larvae can be found HERE. The fascinating images of a D. hominis larva being removed are courtesy of Dr. Carlos Chaccour. He used soap paste to suffocate the larva and facilitate its removal. Check out the video of the larva prior to removal HERE. If you look closely, you can see the larva moving within it's cavity in the skin. HERE is another video from a different case of an extracted larva.