'' Botflies deposit eggs on a host, or sometimes use an intermediate vector such as the common
housefly, mosquitoes, and, in the case of
D. hominis, a species of
tick. After mating, the female botfly captures the
phoretic insect by holding onto its wings with her legs. She then makes the slip—attaching 15 to 30 eggs onto the insect or arachnid's abdomen, where they incubate. The fertilized female does this over and over again to distribute the 100 to 400 eggs she produces in her short adult stage of life of only 8–9 days. Larvae from these eggs, stimulated by the warmth and proximity of a large mammal host, drop onto its skin and burrow underneath. Intermediate vectors are often used since many animal hosts recognize the approach of a botfly and flee. Eggs are deposited on larger animals'
skin directly, or the larvae hatch and drop from the eggs attached to the intermediate vector; the body heat of the host animal induces hatching upon contact or immediate proximity. Some forms of botfly also occur in the
digestive tract after ingestion by licking. '') Myiasis can be caused by larvae burrowing into the skin (or tissue lining) of the host animal. Mature larvae drop from the host and complete the
pupal stage in the soil. They do not kill the host animal, thus they are true
parasites. The equine botflies present seasonal difficulties to
equestrian caretakers, as they lay eggs on the insides of horses' front legs on the
cannon or metacarpal bone (below the knee) and
knees, and sometimes on the
throat or
nose depending on the species. These eggs, which look like small, yellow drops of paint, must be carefully removed during the laying season (late summer and early fall) to prevent infestation in the horse. When a horse rubs its nose on its legs, the eggs are transferred to the mouth and from there to the
intestines, where the larvae grow and attach themselves to the stomach lining or the small intestine. The attachment of the larvae to the tissue produces a mild irritation, which results in erosions and ulcerations at the site. Removal of the eggs (which adhere to the host's hair) is difficult since the bone and
tendons are directly under the skin on the cannon bones; eggs must be removed with a sharp knife (often a razor blade) or rough sandpaper and caught before they reach the ground. The larvae remain attached and develop for 10–12 months before they are passed out in the feces. Occasionally, horse owners report seeing botfly larvae in horse manure. These larvae are cylindrical and are reddish-orange. In one to two months, adult botflies emerge from the developing larvae and the cycle repeats itself.
Cuterebra fontinella, the mouse botfly, parasitizes small mammals all around North America.
Dermatobia hominis, the human botfly, occasionally uses humans to host its larvae. ==As human food==