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Dermatobia hominis (Linnaeus Jr., 1781) (Diptera: Oestridae)

Dermatobia hominis, also known as the Human Bot Fly, the American Warble Fly, and Torsalo is a Neotropical species which employs an extraordinary mechanism to parasitize its vertebrate hosts. D. hominis is endemic to the region extending from south of Mexico to northern Argentina and Chile. Adults range in size from 10-15 mm; are metallic, bluish-black in body color; have brown wings; and display yellow markings on the face and legs (Linnaeus Jr.’s original description). A rather conspicuous fly, given its size and coloration, this obligate parasite uses a process called phoresis (to carry or wear) in which another fly species becomes a vector for the transfer of D. hominis larvae to a suitable host. More specifically, following copulation a bot fly female will capture a mosquito, or in most cases some other hematophagous (blood-feeding) fly, in mid air where she proceeds to glue 10-50 eggs to its abdomen. These temperature-sensitive eggs develop and hatch in response to heat from the vertebrate host on which the vector feeds or lands. The larva may enter through the bite (or other) wound, along a hair follicle (West, Stanford website), or according to some reports, burrow directly into cutaneous tissue (Marinho et al., 2003) where the larva develops. The third-instar larva drops from its host 5-10 weeks later, burrows into the ground, pupates, and molts after 4-11 weeks to produce an adult bot fly. This process whereby tissues of a host are parasitized by a fly is known as myiasis (see link provided for more information). Although parasitism by D. hominis larvae is rarely fatal or even of serious detriment to the health of the host, all three larval stages develop in the cutaneous tissues of the host for up to 10 weeks (Tsuda, et al., 1996) thus producing a painful "warble" or tumor. In rare cases, myiasis can occur in body cavities such as the eyes, ears or nose. The warble if proximal to the brain can cause meningitis leading to death (Noutis & Millikan, 1994). Parasitism of cattle by D. hominis can also affect milk and meat yields as well as leather quality. In fact, production losses in Brazil cost between $200-$260 million (USD) per year (Grisi et al., 2002). D. hominis, unlike most other species of bot fly which are host-specific, can infect a variety of hosts to include humans, cattle, dogs, monkeys, swine (Cogley & Cogley, 1989) and in some cases even tucans and turkeys (Sambon, 1922). Please explore the links below which provide other detailed information.

Illustrations & Photos | Distribution | Vectors | Eggs | Myiasis | Literature

Content by Jonathan M. Eibl and Norman E. Woodley. Last Updated: August 31, 2004.