Cuterebra fontinella

Geographic Range

Mouse bot flies (Cuterebra fontinella) can be found across the eastern United States and some regions of Canada (Nova Scotia, Ontario, Quebec, New Brunswick, Manitoba). Their range extends as far west as central North Dakota. The range continues southward to central Texas. From there they are found as far east as the Atlantic Ocean. Bot flies can be found as far south as Florida.

They are Nearctic and specifically native to North America. (Cameron, 1926; Sabrosky, 1986)


Adult mouse bot flies can be found at the edges of forests, especially around rodent dens, where they lay their eggs. These flies require ambient temperatures above 20 °C to be able to fly. They also require substantial sunlight.

Larval bot flies take residence within a host. They bury themselves within a host, the most typical being white-footed mice (Peromyscus leucopus). They also use hosts such as black rats (Rattus rattus), deer mice (Peromyscus maniculatus), golden mice (Ochrotomys nuttalli), cotton mice (Peromyscus gossypinus), and humans (Homo sapiens). The bot fly larvae burrow into the genital region of the mouse in the dermal tissue. They also develop a breathing hole at the surface of the skin to be able to breathe. From there, larvae will grow and emerge from the host via the breathing hole and burrow themselves in the ground. They metamorphose into pupae and remain underground for several months before emerging as adult flies.

There are no known reports of a typical elevation at which these bots live. (Cameron, 1926; Cogley, 1991; Jaffe, et al., 2005; Sabrosky, 1986; Slansky, et al., 2008; Wolf and Batzil, 2001)

Physical Description

As adults, mouse bot flies have yellow and black hair on their bodies. Amongst the yellow hair there is usually a black spot on the dorsal side of their heads. Females tend to have brighter, almost white hairs. The bright yellow hair and this black spot are unique identifiers, as others in the genus have darker hair or white hair. Furthermore, their eyes are solid black, while other species in the genus possess red spots in their eyes.

Adults measure 15.5 mm to 19 mm. Females tend to be larger than males, measuring up to 4 mm longer than males. Their wingspan averages 13 mm.

Larvae can grow to be 22 mm long and 13.9 mm wide. They are a dark brown-grey color and have a plated body to protect them from potential predators. Pupae have not been well-described. (Gingrich, 1981; Hadwen, 1915; Sabrosky, 1986; Wolf and Batzil, 2001)

  • Sexual Dimorphism
  • female larger
  • sexes colored or patterned differently
  • Range length
    15.5 to 19 mm
    0.61 to 0.75 in
  • Average wingspan
    13 mm
    0.51 in


Mouse bot flies rely on rodent host species for their developmental cycle. Females lay eggs near rodent dens and, upon hatching, larvae burrow into the skin of passing rodents. On average, larvae are 22 mm long and 13.9 mm wide. Individuals hatch at different times, to prevent an entire cluster of eggs attaching to the same host. This also reduces the chances of all larvae attaching to an undesirable host species. Heat and friction are catalysts for eggs hatching and will cause them to hatch quicker. Cold temperatures inhibit the hatching and growth of the eggs.

Larvae burrow into the host through any orifice or open wound. They then migrate through the body, typically settling underneath the skin near the genitals of their hosts. They form a warble - an assemblage of pores and capsules that aid in development - with a cavity that contains each bot fly larva. The pores of each warble act as holes for developing larvae to breathe. Capsules encase the cavities containing the larvae. This capsule layer gets thicker as the larvae develop, due to the attempts of host animals to heal the wounds caused by larvae.

After 20-30 days, developed bot fly larvae exit their hosts through pores of their warble and settle into soil substrate. When they enter soil, larvae form a cocoon and enter their pupal stage. This is a state of diapause that ends when warmer months return, at which point they pupate. The duration between diapause and the pupation process can be anywhere from one month to twelve months long. After pupating, adult flies measure an average of 30 mm long. Adult flies live approximately two weeks and do not feed; instead they focus solely on reproduction. They mate and lay eggs, beginning the cycle for the next generation. (Cogley, 1991; Colwell, 2001; Gingrich, 1981; Johnson, et al., 2018; Sabrosky, 1986)


Mating systems of mouse bot flies are not well known. Due to their short adult lifespan, they are thought to be monogamous.

Once a year, males congregate in an area to wait for females. It is unclear what triggers the congregation - whether it is predetermined or if there is some particular stimulus. Mouse bot flies lay their eggs outside of mice dens to improve the chances of hatched larvae finding a host.

The ovipositors of mouse bot flies are horseshoe shaped and small compared to other flies in the family Oestridae.

Mouse bot flies are not able to fly in colder temperatures, so they come together to mate when it is sunny and a moderate temperature (above 20 °C.) Males patrol their area as they do when protecting their territory, flying when there is sunlight. Females fly less frequently, and only to find a landing site where males can reach them. Intercourse typically lasts around 3 minutes. (Colwell, 2001; Hadwen, 1915; Hunter and Webster, 2012; Sabrosky, 1986; Shiffer, 1983; Wolf and Batzil, 2001)

Mouse bot flies are sexually mature in their adult stage, which can take 2 - 12 months to reach. They breed in summer months at ambient temperatures above 20°C. Like all flies, fertilization happens internally, with females using their ovipositor to gather sperm from males.

Unlike other flies, mouse bot flies need several days after emerging from their pupated state to be able to lay eggs. Female flies die soon after laying eggs. It is estimated that females lay about 2,000 eggs in the breeding season.

To reduce the chances of all larvae burrowing into an unsuitable host, eggs do not hatch at the same, but rather in a staggered fashion. Larvae are immediately independent upon hatching.

There are no known reports of gestation period or birth mass as of 2022. (Colwell, 2001; Sabrosky, 1986)

  • Breeding interval
    Mouse bot flies breed once a year in the summer.
  • Breeding season
    Mouse bot flies breed in the summer at temperatures above 20°C.
  • Average eggs per season
  • Range time to independence
    0 to 0 days
  • Range age at sexual or reproductive maturity (female)
    2 to 12 months
  • Range age at sexual or reproductive maturity (male)
    2 to 12 months

Adults die approximately two weeks after emerging from their pupal stage, during which time they reproduce and lay eggs. After females lay their eggs, there is no further parental involvement in the development of bot flies. Newly hatched larvae are completely independent. (Colwell, 2001; Sabrosky, 1986)

  • Parental Investment
  • no parental involvement


Adult mouse bot flies have an average lifespan of approximately two weeks in the wild. Larvae typically stay within a host for 20-30 days, after which they burrow into the ground and pupate. Pupation lasts between 2 and 10 months depending on the season and climate in which the larvae burrow into the ground.

Mouse bot flies are not kept in captivity, due to the difficulty of replicating the conditions for pupation. The longest known lifespan in the wild is 11 months. (Cogley, 1991; Colwell, 2001; Sabrosky, 1986)

  • Range lifespan
    Status: wild
    11 (high) months


Mouse bot flies are parasites that burrow into the skin of their host. After they leave their host, they burrow into the ground to pupate. They enter a state of diapause, similar to hibernation when temperatures are cool - during late fall, winter months, and early spring months.

The typical host species for mouse bot flies are white-footed mice (Peromyscus leucopus). Atypical hosts include black rats (Rattus rattus), golden mice (Ochrotomys nuttalli) and cotton mice (Peromyscus gossypinus). Larval bot flies burrow into the skin near the genitals of their host. There have also been a few cases of mouse bot flies reported in humans (Homo sapiens), where larvae were found in the forehead area.

Mouse bot flies don't socialize with each other outside of mating. They are solitary as larvae due to their parasitic nature. Their short lifespan is spent mostly in solitude as a result of their parasitism and staggered stages of development.

Adult mouse bots are diurnal, active during the day, at temperatures above 20 °C. Adult males will patrol their territory during the day, but will only fly when there is sunlight, or for short periods when the sun is covered (about 15 minutes). Females do not fly unless they are looking for a mate.

When another mouse bot fly or other flying insect enters their territory, males attack and attempt to bring the intruder to the ground. If they can not directly attack the intruders, they chase the intruder out of their territory. (Colwell, 2001; Sabrosky, 1986; Shiffer, 1983; Slansky, et al., 2008; Wolf and Batzil, 2001)

  • Average territory size
    4.12 m^2

Home Range

Home range has not been quantified for adult mouse bot flies. Adult males are territorial during their 2 weeks of life, and territory size has been estimate at 4.12 m^2. (Colwell, 2001)

Communication and Perception

There is not much documented about communication between individual mouse bot flies or between mouse bot flies and other bot fly species.

Mouse bot flies tend to congregate for two weeks in the summer to mate. The specific weeks vary as it depends on when the pupation period ends. It is unknown what draws the males to congregate in a specific area; most literature suggests it is some chemical signaling. Males release pheromones that attract females and display to females by flying around. Males also guard their territories and will attack or chase insect intruders.

Mouse bot flies have compound eyes that allow them to distinguish shades of colors and respond quickly to external visual stimuli. They use tactile communication to find their mate and procreate, as well as find their way through a host. (Sabrosky, 1986; Sebeok, 1977; Wicker-Thomas, 2007)

Food Habits

Bot fly larvae feed off of the flesh and bodily fluids of the hosts in which they reside. In the case of mouse bot flies specifically, their main host is white-footed mice (Peromyscus leucopus). After feeding off of their host for 20-30 days, they will exit and pupate underground. Mouse bot flies do not feed as pupa. As adults, they lack a mouth, surviving off of stored energy from their larval stage. (Cramer, 2006; Cramer and Cameron, 2006; Durden, 1995; Sabrosky, 1986)

  • Animal Foods
  • mammals
  • blood
  • body fluids


The parasitic lifestyle of mouse bot flies is an anti-predation tactic. Also, by burrowing in the ground to pupate, they reduce their chances of discovery by predators. Adult mouse bot flies are colored yellow and black to mimic a bee, tricking potential predators into thinking they can sting.

Predation is likely rare for mouse bot flies as they are adults flies for just two weeks. No predators of these bot flies have been reported in literature. (Hadwen, 1915; Hunter and Webster, 2012; Sabrosky, 1986)

  • Anti-predator Adaptations
  • mimic

Ecosystem Roles

Mouse bot flies have a parasitic life cycle which has a negative effect on the ecosystems they inhabit. They feed off of rodent hosts. The typical hosts, white-footed mice, (Peromyscus leucopus), have evolved to survive after being parasitized. Atypical hosts include black rats (Rattus rattus), golden mice (Ochrotomys nuttalli), deer mice (Peromyscus maniculatus), and cotton mice (Peromyscus gossypinus). Although black rats may not have not specifically evolved to survive this parasite, many do. (Cogley, 1991; Colwell, 2001; Cramer, 2006; Durden, 1995; Gingrich, 1981; Jaffe, et al., 2005; Jennison, et al., 2006; Johnson, et al., 2018; Sabrosky, 1986; Slansky, et al., 2008; Wolf and Batzil, 2001)

Species Used as Host

Economic Importance for Humans: Positive

Mouse bot flies provide no known economic benefits to humans.

Economic Importance for Humans: Negative

Rarely, mouse bot flies have parasitized humans. Removing these parasites requires medical attention, which can be costly.

Mouse bot flies can also inhabit domesticated animals, and removal requires veterinary assistance. These appointments tend to be more costly than that of removal from human hosts. Removal of one or two flies in dogs costs an average of $200. More substantial infestations can exceed $2,000. Eradication of infestations in cats tend to cost $200-$600. (Cogley, 1991; Colwell, 2001; Cramer, 2006; Durden, 1995; Gingrich, 1981; Jennison, et al., 2006; Johnson, et al., 2018; Sabrosky, 1986; Slansky, et al., 2008)

Conservation Status

Mouse bot flies have no special status on the U.S federal list, CITES, or the State of Michigan list. These flies have not been evaluated by the IUCN Red List.

No conservation efforts are currently in place for mouse bot flies. While they can harm domestic animals, wild animals, and occasionally humans, there are no widespread efforts to control populations of this bot fly species.

A threat to this species are forest and pasture fires. Mouse bot flies are very sensitive to temperature and the change in temperature of the soil causes larvae or pupae to die. (Boggs, et al., 1991; Colwell, 2001)


Dave Brown (author), Radford University, Sierra Felty (editor), Radford University, Bianca Plowman (editor), Radford University, Karen Powers (editor), Radford University, Victoria Raulerson (editor), Radford University, Christopher Wozniak (editor), Radford University, Genevieve Barnett (editor), Colorado State University, Galen Burrell (editor), Special Projects.



living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.


an animal that mainly eats meat

causes or carries domestic animal disease

either directly causes, or indirectly transmits, a disease to a domestic animal


uses smells or other chemicals to communicate


a period of time when growth or development is suspended in insects and other invertebrates, it can usually only be ended the appropriate environmental stimulus.

  1. active during the day, 2. lasting for one day.

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature


union of egg and spermatozoan


forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.


Referring to a burrowing life-style or behavior, specialized for digging or burrowing.


the state that some animals enter during winter in which normal physiological processes are significantly reduced, thus lowering the animal's energy requirements. The act or condition of passing winter in a torpid or resting state, typically involving the abandonment of homoiothermy in mammals.

internal fertilization

fertilization takes place within the female's body


A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.


Having one mate at a time.


having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.


reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.


an organism that obtains nutrients from other organisms in a harmful way that doesn't cause immediate death


chemicals released into air or water that are detected by and responded to by other animals of the same species


an animal that mainly eats blood

seasonal breeding

breeding is confined to a particular season


offspring are all produced in a single group (litter, clutch, etc.), after which the parent usually dies. Semelparous organisms often only live through a single season/year (or other periodic change in conditions) but may live for many seasons. In both cases reproduction occurs as a single investment of energy in offspring, with no future chance for investment in reproduction.


reproduction that includes combining the genetic contribution of two individuals, a male and a female


lives alone


uses touch to communicate


that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).


Living on the ground.


defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement


uses sight to communicate


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Cogley, T. 1991. Warble development by the rodent bot Cuterebra fontinella (Diptera: Cuterebridae) in the deer mouse. Veterinary Parasitology, 38/4: 275-288.

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Cramer, M. 2006. The Effects of Bot Fly (Cuterebra fontinella) Parasitism on the Ecology and Behavior of the White-footed Mouse (Peromyscus leucopus). (Master's Thesis). Cincinnati, Ohio: University of Cincinnati.

Cramer, M., G. Cameron. 2006. Effects of bot fly (Cuterebra fontinella) parasitism on a population of white-footed mice (Peromyscus leucopus). Journal of Mammalogy, 87/6: 1103-1111.

Durden, L. 1995. Bot fly (Cuterebra fontinella fontinella) parasitism of cotton mice (Peromyscus gossypinus) on St. Catherines Island, Georgia. The Journal of Parasitology, 81/5: 787-790.

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Wicker-Thomas, C. 2007. Pheromonal communication involved in courtship behavior in Diptera. Journal of Insect Physiology, 53/11: 1089-1100.

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