The botfly (Dermatobia hominis), native to Central and South America, must utilize a human or other mammal host to live out its larval stage prior to transforming into a fly. Travelers to the botfly's habitat often bring back the larvae in their subcutaneous skin layers. If you're traveling to regions known to have a high population of botflies, you must take extra precautions, such as applying insecticidal sprays and wearing long sleeves with long pants to cover exposed skin regions.
Botflies measure a little under one inch in length. The hairy flies resemble bumblebees. The botfly's face is yellow, its legs orange and its body black with gray fur. The fly's abdomen is a brilliant metallic blue.
The adult female botfly catches a mosquito or muscoid fly. She does not kill the unlucky insect, but lays eggs on its body, according to the Centers for Disease Control and Prevention. The virtually microscopic eggs appear creamy in color and oval in shape. The female botfly normally sticks her eggs on the sides of the blood-sucking insect's body. The eggs hatch into small larvae on the insect. The larvae remain on the host insect until it lands on a human or other mammal to take a blood meal.
Once the mosquito or muscoid fly begins to feed, the larvae leave the insect and quickly penetrate the skin of the human or other mammal through the bite hole left by the mosquito or muscoid fly. Rarely, the larvae will utilize a hair follicle to gain entrance into the skin. They will feed within the subdermal cavity they create just below the skin's surface. The larvae breath air using two barely noticeable posterior spiracles that stick out of the skin's surface.
The larvae will molt seven days after entering the host's body. They will continue to feed on the host's tissue for another 18 days before undergoing one last molt to reach their final size. The larvae will remain in the host's body for an additional 30 days before burrowing out of the host's skin and falling to the ground to pupate (transform into a pupa) within the soil, according to the University of Florida.
The pupate stage of the botfly takes approximately two to three weeks. Once the pupate stage passes, the botfly emerges from the soil as an adult. It will quickly seek out another botfly to mate with before it perishes. The adult's lifespan is only one to nine days, according to the Merck Veterinary Manual.