The bot fly is not your average housefly. The various species can be described as myiatic flies, meaning they invade living tissue or organs of humans and animals when they are still in their larvae stage. In their adult form, species like the Horse Stomach bot fly Gasterophilus intestinalis resemble honey bees and are about 18 millimeters in length. The larvae of most species are usually red or light yellow in the early stages with rows of spines covering the body.
Where to find them:
Bot flies like the Human bot fly are native to Central and South America. They can also be found in northern Argentina and Trinidad. Species like the Horse Stomach bot fly are found worldwide.
The Human bot fly regularly infests humans and a wide range of animal hosts, especially cattle. Infections with myiatic flies start out as itchy sores that develop into painful boil-like lesions that often ooze. When the bot fly is discovered, it is surgically removed and those who are affected are usually monitored for additional lesions.
The red larvae of the Horse Stomach bot fly develop by clustering in various areas of the animal’s stomach. Some species remain attached to the flesh by their mouth hooks for up 12 months until they mature.
The parasite completes one generation each year. After the adult flies copulate, the pregnant female deposits her eggs on the hairs of the forelegs and chest area in the case of the Horse Stomach bot fly. The eggs usually hatch within a week.
In the case of the Human bot fly, the female fly captures another blood-sucking insect like a tick or a mosquito and glues her eggs to its abdomen. When the carrier feeds, the larvae hatch and penetrate the host’s skin. After six weeks of development, the larvae emerge and pupate on the soil. The entire cycle takes around three months.