Botflies live on every continent except Antarctica, though the species people worry about most, the human botfly, is confined to tropical and subtropical regions stretching from southern Mexico to Argentina. The broader botfly family (Oestridae) includes dozens of species adapted to remarkably different environments, from equatorial rainforests to Arctic tundra, and from Mediterranean pastureland to the deserts of the Sahara. Where you are likely to encounter one depends entirely on which species is in question and which animals share the landscape with you.
The Human Botfly and Its Neotropical Range
The species most people mean when they say “botfly” is Dermatobia hominis, sometimes called the torsalo or berne. It is native to tropical and subtropical Central and South America and is widely distributed throughout the Americas, from the southern regions of Mexico to Argentina.1PubMed Central. Imported and Autochthonous Cases of Myiasis Caused by Dermatobia hominis: Taxonomic Identification Using the Internal Transcribed Spacer Region Dense, humid lowland forests and agricultural fringe areas are its preferred habitats. The fly thrives where warmth, moisture, and abundant blood-feeding insects intersect, because it depends on mosquitoes and other biting flies to deliver its eggs to a host.
Rather than landing directly on a person or animal, the female Dermatobia captures a smaller fly or mosquito in midair and glues her eggs onto it. When that carrier insect later lands on warm skin to feed, body heat triggers the eggs to hatch, and the larvae burrow in.2PubMed Central. First record of Psorophora ferox (Diptera: Culicidae) infested with eggs of Dermatobia hominis (Diptera: Cuterebridae), in Ucayali: Peru This hitchhiking strategy, called phoresis, ties the human botfly’s range tightly to areas where blood-feeding insects are abundant year-round. You will not find established populations in dry highlands or temperate cities, because the carrier insects the botfly relies on do not thrive there.
Within its range, infestation rates tend to spike in lowland rainforest zones popular with ecotourists. One study of returning Israeli travelers found that 80% of myiasis cases were acquired in Latin America, with over half of those traced to the Madidi National Park area in Bolivia’s Amazon basin.3Journal of Travel Medicine. Myiasis in Travelers The remaining 20% of cases in that study were acquired in Africa, involving different fly species. For the human botfly specifically, the Amazon basin and Central American lowland forests represent the highest-risk zones.
North American Botflies That Target Rodents and Rabbits
The United States and Canada have their own native botflies, though they rarely make headlines because they almost never parasitize humans. The genus Cuterebra includes roughly 30 species across North America, and their larvae develop under the skin of wild rodents and rabbits. In Florida alone, five Cuterebra species have been documented. Four of those have broad ranges stretching across much of the continent, while one, Cuterebra cuniculi, appears restricted to southern Georgia and Florida.4Florida Entomologist. Cuterebra Bot Flies (Diptera: Oestridae) and Their Indigenous Hosts and Potential Hosts in Florida
These flies inhabit forest edges, meadows, and brushy areas where their rodent and lagomorph hosts nest. Female Cuterebra lay eggs near burrow entrances or along runways that mice and rabbits use regularly. When a small mammal brushes past, the larvae latch on. Domestic cats and dogs sometimes pick up Cuterebra larvae by investigating rodent burrows, which is how most pet owners in temperate North America first learn that botflies exist close to home. If you live anywhere from Florida to southern Canada and your outdoor cat comes home with a mysterious lump, a Cuterebra larva is a real possibility in the warmer months.
Adult Cuterebra have an interesting habitat preference during mating season. Males congregate on bare, elevated ridgetop perching sites, a behavior called hilltopping. Research on Cuterebra austeni found that the same ridgetop locations served as mating sites over at least 22 years, with males drawn specifically to locally elevated, vegetation-free spots.5Journal of Insect Behavior. Long-Term Stability in the Mating System of the Bot Fly Cuterebra austeni (Cuterebridae) Individual flies even returned to exact perching spots after being captured, marked, and released. That kind of site fidelity means these flies are loyal to very specific patches of habitat, not just general areas.
Livestock Botflies Across the Northern Hemisphere
Cattle, horses, sheep, and goats each have their own dedicated botfly parasites, and these species have followed domesticated herds across the globe for millennia.
Cattle Warble Flies
The genus Hypoderma, commonly known as warble flies, causes a condition called hypodermosis in cattle. Female flies lay eggs on the legs and lower body of cattle; the hatching larvae burrow through tissue and migrate through the animal’s body over months before settling under the skin of the back, where they form the characteristic bumps (“warbles”) and eventually drop out to pupate in the soil. Hypodermosis is an endemic parasitic disease common in countries across the northern hemisphere.6PubMed Central. Epidemiological Surveillance of Hypodermosis in Cattle from Romania Historically, warble flies were a serious pest across Europe and North America. Eradication programs in western Europe and parts of North America have dramatically reduced their numbers, though they persist in eastern Europe, Central Asia, and parts of China.
Horse Stomach Bots
The genus Gasterophilus includes several species whose larvae develop inside the stomachs and intestines of horses and donkeys. Adult females glue tiny yellow eggs to the hairs on a horse’s legs, chest, or muzzle. When the horse licks or rubs the area, the larvae enter the mouth and eventually attach to the stomach lining. These flies are found virtually everywhere horses are kept, from the Americas to Europe to Asia and Australia. Research in Romania documented widespread Gasterophilus infection across the country’s territory, highlighting ongoing welfare concerns for horses.7PubMed Central. Gasterophilus in horses from Romania: diversity, prevalence, seasonal dynamics, and distribution Horse owners in temperate climates learn to recognize the tiny eggs on their animals’ legs in late summer and fall, and routine deworming protocols in equine care exist largely because of these parasites.
Sheep Nose Bots
Oestrus ovis, the sheep botfly, takes a different approach: rather than laying eggs, the female fly deposits live first-stage larvae directly into a sheep’s nostrils. The larvae then crawl up into the nasal passages and sinuses, where they feed, grow, and eventually sneeze out to pupate in soil. This parasite is described as cosmopolitan, meaning it occurs across a wide geographic range, and is especially widespread in hot and dry regions including countries bordering the Mediterranean Sea.8Emerging Infectious Diseases. Oestrus ovis Nasal Myiasis with Pupation in Human Host, Greece, October 2025 Studies have documented its dynamics in habitats ranging from the Egyptian Nile Delta to the desert margins on either side of it.9Veterinary Parasitology. The distribution and seasonal dynamics of Oestrus ovis linne infesting the nasal cavities and sinuses of sheep in egypt
Oestrus ovis is endemic wherever sheep and goats are raised in warm, arid climates.10Small Ruminant Research. Oestrosis: Parasitism by Oestrus ovis Shepherds in Mediterranean countries, North Africa, the Middle East, and parts of South Asia all deal with this fly. Unlike many other botfly species, Oestrus ovis can occasionally strike humans. The fly sometimes mistakes a person’s eye or nose for a sheep’s nostril and deposits larvae there, a condition called ophthalmomyiasis when it involves the eye. Cases in humans tend to cluster in rural sheep-rearing areas during the fly’s active season.
Desert Specialists and the Camel Botfly
Not all botflies need lush forests. Cephalopina titillator, the camel nasal botfly, inhabits some of the driest environments on earth. Ecological niche modeling has shown that this species is most frequently found in arid and semi-arid regions of North Africa, the Middle East, and the Horn of Africa. Precipitation during the wettest month turned out to be the strongest predictor of where the fly occurs, contributing over 40% to the model’s accuracy.11PubMed. Morphological characterization of genital structures and sexual dimorphism in Cephalopina titillator (Diptera: Oestridae) with implications for climate change adaptation Even in deserts, the fly needs a minimum amount of seasonal moisture to complete its life cycle in the soil.
The camel botfly’s life strategy mirrors that of the sheep nose bot: adult females deposit larvae into the nostrils of camels, where they develop in the nasal sinuses. Wherever dromedary or Bactrian camels are herded, from Mauritania to Pakistan, this fly tends to follow. It is a good reminder that botflies are not just a tropical-forest phenomenon. Any environment that sustains a large warm-blooded host population can support a botfly species adapted to exploit it.
Arctic Tundra and Reindeer Botflies
Perhaps the most surprising botfly habitat is the Arctic. Two species parasitize reindeer and caribou across the circumpolar north: the reindeer warble fly (Hypoderma tarandi) and the reindeer nose bot (Cephenemyia trompe). Research on semi-domestic reindeer in Norway tracked both species over multiple years, collecting over two thousand warble fly larvae and hundreds of nose bot larvae from reindeer yearlings.12Rangifer. The timing and departure rate of larvae of the warble fly Hypoderma (= Oedemagena) tarandi (L.) and the nose bot fly Cephenemyia trompe (Modeer) (Diptera: Oestridae) from reindeer
These flies have adapted to a narrow window of activity during the short Arctic summer. Adults emerge, mate, and oviposit in the span of a few weeks when temperatures are warm enough for flight. Hypoderma tarandi lays eggs on reindeer leg hairs, and the resulting larvae migrate through the animal’s body over the winter, eventually surfacing along the back in spring. Cephenemyia trompe squirts live larvae into the reindeer’s nostrils; they develop in the nasal passages and are eventually sneezed or coughed out. For indigenous herding communities such as the Sámi, these parasites are a familiar and sometimes serious threat to herd health. Heavy infestations can weaken animals, damage hides, and reduce the value of reindeer products.
The Arctic botflies’ range covers Scandinavia, northern Russia, Alaska, and northern Canada, essentially wherever wild caribou or domesticated reindeer exist. Climate change is a concern here. Warmer Arctic temperatures could extend the active season for adult botflies, increase the number of generations per year, or allow the flies to colonize higher latitudes and altitudes where reindeer herds have historically been less parasitized.13PubMed Central. Biting insects in a rapidly changing Arctic
Why Travelers Encounter Botflies Outside Their Native Range
Botflies do not establish breeding populations outside their natural range, but their larvae can travel inside people. A tourist bitten in the Amazon may not notice anything unusual until weeks later, when a growing larva under the skin produces a painful, boil-like lump back home in New York or London. The human botfly, Dermatobia hominis, is native to Central and South America and is regularly seen in travelers returning from endemic regions to temperate countries including the United States and Europe.14PubMed. The Botfly, A Tropical Menace: A Distinctive Myiasis Caused by Dermatobia hominis Physicians in non-endemic countries may not immediately recognize the lesion, since furuncular myiasis (a boil caused by a fly larva) is not something they encounter routinely.15PubMed Central. Cutaneous furuncular myiasis: Human infestation by the botfly.
The most common travel destinations associated with human botfly cases are lowland jungle areas of Bolivia, Brazil, Belize, Costa Rica, and Peru. The Amazon basin features disproportionately in case reports because it combines the right climate, dense mosquito populations to serve as egg carriers, and a steady stream of ecotourists spending time outdoors in short sleeves. Africa accounts for a smaller share of travel-associated myiasis cases, and those tend to involve different fly genera such as Cordylobia (the tumbu fly), not Dermatobia. If you are planning a trip to a tropical forest in the Americas and want to reduce risk, the practical advice is covering exposed skin, using insect repellent, and sleeping under a mosquito net, since the same mosquitoes that transmit malaria are the ones that can ferry botfly eggs.
How Livestock Movement Shaped Botfly Geography
The present-day distribution of livestock botflies is not purely natural. For thousands of years, human migrations carried domesticated animals and their parasites into new territories. The Mediterranean region served as a crossroads for commercial trade routes in early Western civilization, and the movement of sheep, goats, cattle, and horses across this area over more than three thousand years helped shape the evolution and distribution of parasitic botfly species.16PubMed Central. Human and livestock migrations: a history of bot fly biodiversity in the Mediterranean region This means the ranges of flies like Oestrus ovis and Gasterophilus species today partly reflect ancient trade routes and pastoral movements, not just climate suitability alone.
This historical dimension matters because it explains why some botfly species seem oddly cosmopolitan. Gasterophilus, for instance, infests horses on nearly every continent where horses are found, including Australia, where horses are not native. The flies came with the horses. Similarly, Oestrus ovis follows sheep wherever they are herded, from the Atlas Mountains to the Scottish Highlands. Eradication is difficult precisely because these flies have been embedded in livestock systems for so long that reintroduction from neighboring regions is almost inevitable after any local control effort.
Climate Change and Shifting Ranges
Several botfly species appear poised to expand their ranges as global temperatures climb. The camel nasal botfly modeling discussed earlier projects continued range expansion across the Sahel and East Africa under high-emissions climate scenarios, with contractions at the northern edges of its current range.11PubMed. Morphological characterization of genital structures and sexual dimorphism in Cephalopina titillator (Diptera: Oestridae) with implications for climate change adaptation In the Arctic, warming is expected to benefit reindeer botflies by lengthening the summer flight season and potentially allowing the flies to persist at higher elevations.
For the human botfly, direct range expansion northward is less certain. Dermatobia hominis depends on a chain of conditions: tropical warmth, abundant carrier insects, and suitable hosts. A modest warming in, say, the southern United States would not automatically import the whole ecosystem the fly needs. The greater concern is that increased travel to endemic regions, combined with unfamiliarity among healthcare providers in temperate countries, will lead to more imported cases being misdiagnosed or diagnosed late. The flies themselves are unlikely to colonize New York or Paris, but more tourists may bring larvae home.
Habitats at a Glance by Species Group
Pulling together the geographic threads, the major botfly groups sort neatly by the environments their hosts occupy:
- Tropical lowland forests: Dermatobia hominis (human botfly), southern Mexico through Argentina, tied to humid areas with dense mosquito populations.
- Temperate forests and meadows: Cuterebra species (rodent and rabbit bots), across North America from Florida to southern Canada.
- Pastureland worldwide: Gasterophilus species (horse stomach bots), found wherever horses are managed.
- Hot, arid grazing land: Oestrus ovis (sheep nose bot), cosmopolitan in warm, dry sheep-raising regions; Cephalopina titillator (camel nose bot), arid North Africa, Middle East, and Horn of Africa.
- Northern hemisphere cattle country: Hypoderma species (cattle warble flies), historically across Europe, Russia, and North America, now reduced in the west.
- Arctic and subarctic tundra: Hypoderma tarandi and Cephenemyia trompe (reindeer warble and nose bots), circumpolar wherever caribou and reindeer range.
The common denominator is not a climate zone or a vegetation type but a reliable host population. Botflies are specialist parasites, and their habitats are defined less by temperature or rainfall in isolation than by where their preferred host animals live, breed, and rest. A species adapted to camel nostrils has no use for a rainforest, and a species dependent on tropical mosquitoes for egg delivery cannot function on the tundra. Each botfly lineage has solved the problem of finding and infesting a host in a different way, and those solutions lock each species into the habitat where its strategy works.