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Cuterebra buccata

By Dave Brown

Geographic Range

Rabbit bot flies (Cuterebra buccata) are primarily Nearctic and native to the eastern United States and Canada. Their range includes much of the east coast from New Hampshire and Long Island, New York, southward through Virginia, Maryland, Tennessee, Georgia, and Florida. They are absent from Maine, Rhode Island, and Vermont. Rabbit bot flies have been documented as far west as North Dakota, Kansas, New Mexico, and Arizona. They have also been reared from rabbits in Texas. There have been additional observations of this species in Wisconsin, northern Illinois, and Iowa.

Rabbit bot flies have been documented in Canada in southern Ontario and Nova Scotia.

Museum records also document one specimen from the state of Querétaro, Mexico, and there are reports of rabbit bot flies as far south as Neotropical regions in Guatemala and Honduras. (GBIF Secretariat, 2022; Sabrosky, 1986)

Habitat

As larvae, rabbit bot flies bury themselves within a mammalian host, the typical host being cottontail rabbits (Sylvilagus floridanus). However, they also use atypical hosts such as snowshoe hares (Lepus americanus) and domestic rabbits (Oryctolagus cuniculus). They have also been reported to use non-native rat species like black rats (Rattus rattus) and Norway rats (Rattus norvegicus).

Rabbit bot fly larvae typically burrow into the hip or groin region of their hosts, but may also settle in the neck and shoulder regions. They develop a breathing hole at the surface of the skin of the host. After feeding on their hosts, larvae emerge from these breathing holes and burrow themselves into the ground. Larvae then metamorphose into pupae and remain underground for several months before emerging as adult flies. Rabbit bot flies can be found on the edges of forests and around the dens of their rodent hosts, where they lay their eggs. Like most bot fly species in the eastern United States, rabbit bot flies are active at ambient temperatures above 20°C and require substantial sunlight.

Elevation ranges for rabbit bot flies have not been reported. (Cogley, 1991; Kaufman and Wood, 2015; Sabrosky, 1986)

Physical Description

Adult rabbit bot flies have a long red stripe and a red dot in their eyes, typical of bot fly species that use hosts in the order Lagomorpha. They have white hair with a pattern of black spots on their face and three spots on their cheeks. These three spots are unique to rabbit bot flies. The most ventral spot is also the largest of the three. The thoraxes of rabbit bot flies are white or light gray with fine hairs. There is also a cluster of black spots along their abdomens.

Female rabbit bot flies have shorter hairs on their thoraxes compared to males. Males measure a total length between 16.5 and 17.5 mm, while females are typically 18 to 20 mm. Reported wingspans are 14.5 to 16.5 mm in males and 16.5 to 18.0 mm in females.

Whereas other bot fly species, such as mouse bot flies (Cuterebra fontinella), possess multiply-pointed spines along their bodies, rabbit bot flies have singly-pointed spines. Rabbit bot fly larvae vary in size by instar. For example, at the beginning of the second instar, they measure about 5.8 mm long by 1.6 mm wide. By the end of the second instar, they measure 10.5 mm by 4.5 mm. At the end of their third instar, they are 26 to 32 mm long, and 13 to 16 mm wide. Rabbit bot fly larvae remain in their hosts for approximately two weeks to complete their three instar stages before leaving hosts to pupate. A study in Georgia reported that pupation time lasted 103 to 129 days. However, the pupal stage can last longer in northern parts of their range. (Colwell, 2001; Knipling and Brody, 1940; Sabrosky, 1986)

  • Sexual Dimorphism
  • female larger
  • sexes shaped differently
  • Range length
    16.5 to 20 mm
    0.65 to 0.79 in
  • Range wingspan
    14.5 to 18 mm
    0.57 to 0.71 in

Development

Rabbit bot flies lay their eggs outside of the dens of their hosts. Upon hatching, larvae burrow into the skin of host animals. Hatching is staggered as an evolutionary defense to prevent an entire cluster of eggs attaching to an atypical host. Heat and friction are a catalyst for eggs hatching and will cause them to hatch quicker. Cold temperatures inhibit the hatching and growth of the eggs.

Larvae burrow into their hosts through any orifice or open wound. They then migrate through the body and settle within the neck, shoulders, posterior, or hips of their rabbit hosts. The rear or genitals of male rabbits are ideal for larval development.

Larvae embedded in a host form a "warble" underneath the skin. Warbles have three parts to them, all of which aid in development. Pores are holes which allow the bots to breathe under the skin of their hosts. Capsules are a thickened layer of host skin that protects the larvae. The capsule layer gets thicker as larvae develop due to the attempts of hosts to heal the open wound. Finally, cavities are the areas in which larvae reside during development.

Rabbit bot fly larvae complete three instars in their hosts. At the beginning of the second instar, they measure about 5.8 mm long by 1.6 mm wide. By the end of the second instar, they are 10.5 mm long by 4.5 mm wide. At the end of their third instar, they are 26 to 32 mm long, and 13 to 16 mm wide. A study in Georgia reported that rabbit bot fly larvae remained in their hosts for roughly two weeks to complete the three instars before leaving hosts to pupate. However, in colder regions this development can take up to 30 days.

After 14 to 30 days, rabbit bot flies exit their hosts through the breathing hole in the warble and settle into soil substrate. Upon entering the soil, larvae will enter diapause in the soil throughout cold periods and exhibit delayed development. Diapause ends when warmer months come, at which point larvae pupate. Depending on regional climate and diapause use, the pupation process can take 1 to 12 months. However, studies in Georgia measured pupation times of 103 to 129 days.

Adult rabbit bot flies live for 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. (Knipling and Brody, 1940; Sabrosky, 1986)

Reproduction

Mating systems of rabbit 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 a predetermined time or if there is some deciding stimulus is unknown. Females lay eggs outside of rabbit dens to improve the chances of hatched larvae finding a host.

The reproductive systems of rabbit bot flies are thought to mirror those of other mammalian-host bot fly species in the genus Cuterebra. Typically, they are not able to fly in colder temperatures, so they will aggregate to mate when it is sunny and above 20 °C. Males fly to patrol and protect a territory from competitors. Females fly less often, and only fly to find a landing site where males can find them. Intercourse typically lasts around 3 minutes. (Colwell, 2001; Hadwen, 1915; Hunter and Webster, 2012; Sabrosky, 1986; Shiffer, 1983)

Rabbit bot flies reach sexual maturity once they reach their adult stage, which can take 2 to 12 months. They breed in summer months at ambient temperatures above 20°C. However, one study found that rabbit bots in southern Georgia experienced two bouts of reproduction per year. In this case, a larva from June pupated for 75 days and then reached adulthood by August of the same year. Then, larvae from November pupated for 103 to 129 days and reached adulthood the following spring, between March and April. It is likely that temperature limits reproductive capability at sites farther north in their range.

Fertilization in rabbit bot flies is internal, as females use their ovipositor to gather sperm from males. Female flies die soon after laying eggs. Although females bots of other species lay about 2,000 eggs in the breeding season, exact brood numbers have not been reported for rabbit bot flies.

Rabbit bot fly eggs do not hatch all at once. Instead, they are staggered to protect all larvae from burrowing into the same unsuitable host, the eggs stagger in their hatching and will not hatch at the same time. Larvae are immediately independent upon hatching.

Incubation period and birth mass for rabbit bot fly larvae are not reported in the literature. (Colwell, 2001; Knipling and Brody, 1940; Sabrosky, 1986)

  • Breeding interval
    Once a year but sometimes two generations/year in souther locales
  • Breeding season
    Temperatures above 20C, typically just a few weeks long
  • Average time to independence
    0 minutes
  • Range age at sexual or reproductive maturity (female)
    2 to 12 months
  • Range age at sexual or reproductive maturity (male)
    2 to 12 months

After female rabbit bot flies lay eggs, there is no further parental involvement with offspring as they develop. Adults die approximately two weeks after emerging from the pupal stage. (Sabrosky, 1986)

  • Parental Investment
  • no parental involvement

Lifespan/Longevity

Adult rabbit bot flies have an average lifespan of approximately two weeks in the wild. Larvae typically stay within a host for 14 to 30 days, after which they exit their host and burrow in the ground to pupate. Pupae remain in the soil for 2 to 10 months depending on season and local climate. For example, in Georgia, pupation was measured from 75 to 129 days; some overwintered as pupae while others emerged in the fall the same year as they hatched.

Rabbit bot flies are not known to be kept in captivity due to the difficulty of replicating the conditions for pupation. The longest known lifespan in the wild is 12 months. (Knipling and Brody, 1940; Sabrosky, 1986)

  • Range lifespan
    Status: wild
    12 (high) months

Behavior

Rabbit bot flies have a parasitic larval stage and, upon emergence from their host, they burrow in the ground to pupate. This makes them fossorial during part of their life cycle. As pupae, rabbit bot flies enter a state of diapause - similar to hibernation - when temperatures are cool during late fall, winter months, and early spring months.

Rabbit bot flies typically use cottontail rabbits (Sylvilagus floridanus) as hosts, burrowing into the rear or hip area. Atypical hosts include snowshoe hares (Lepus americanus), domestic rabbits (Oryctolagus cuniculus), black rats (Rattus rattus), and Norway rats (Rattus norvegicus).

Rabbit bot flies do not socialize with each other outside of mating. They are solitary as larvae and pupae as a result of their parasitism and staggered stages of development.

Adult rabbit bot flies are active during the day at temperatures above 20 °C. Adult males patrol territories during the day, but only fly when there is sunlight, or for short periods (approximately 15 minutes) when the sun is covered. Females do not fly unless they are actively seeking a mate.

If an airborne insect enters the territory of a male rabbit bot fly, the male will attack and attempt to bring the intruder to the ground. If they can not directly attack an intruder, they chase it out of their territory. (Colwell, 2001; Sabrosky, 1986; Shiffer, 1983; Slansky, et al., 2008; Wolf and Batzil, 2001)

Home Range

There is little information on the home range of adult rabbit bot flies. Adult males defend a territory during the few weeks that they are alive and seeking mates. (Colwell, 2001)

Communication and Perception

Little is known about the communication of rabbit bot flies with conspecifics or related bot fly species.

Bot flies congregate for two weeks in warmer months to mate. The specific weeks vary depending on whether the pupation period ends in summer or fall. It is unknown what draws males to congregate in a specific area, although most literature suggests it involves chemical signaling. Males release pheromones that help them attract females and fly around so that females see them. Males also guard territories and will attack or chase insect intruders.

Rabbit bot flies have compound eyes, which allows them to distinguish shades of colors and respond quickly to external visual stimuli. They use tactile communication to find mates and procreate, as well as move through hosts. (Knipling and Brody, 1940; Sabrosky, 1986)

Food Habits

As larvae, rabbit bot flies bury themselves in a host and feed off of the flesh and bodily fluids of that animal. The main host that rabbit bot flies use are eastern cottontails (Sylvilagus floridanus).

Rabbit bot flies do not feed as pupae. As adults they lack a mouth, and thus cannot eat. Instead, they use stored energy from their larval stage to survive for roughly two weeks, during which time they search for mates. (Cramer, 2006; Cramer and Cameron, 2006; Durden, 1995; Sabrosky, 1986)

Predation

Little is known regarding predators of rabbit bot flies. Larvae and pupae avoid predators by burrowing into hosts or the ground, respectively. Predation is likely rare for adult rabbit bot flies, as they are only alive and active for approximately two weeks. (Colwell, 2001; Sabrosky, 1986)

Ecosystem Roles

Rabbit bot flies are parasitic, which can have a negative effect on the ecosystems they inhabit. They typically feed off of hosts in the order (Lagomorpha). Their typical hosts, eastern cottontails (Sylvilagus floridanus), have evolved to survive being parasitized. Atypical lagomorph hosts include snowshoe hares (Lepus americanus) and domestic rabbits (Oryctolagus cuniculus), with the latter being reported to host up to 9 larvae in one individual. One report found that rabbit bot flies can be reared from non-native rats such as black rats (Rattus rattus) and Norway rats (Rattus norvegicus). (Knipling and Brody, 1940; Sabrosky, 1986; Slansky, et al., 2008; Wolf and Batzil, 2001)

Species Used as Host

Economic Importance for Humans: Positive

Rabbit bot flies provide no known economic benefit for humans.

Economic Importance for Humans: Negative

Rabbit bot flies pose a minor health risk to humans. There is one report of larvae found in an elderly man in Connecticut. Multiple bots on this individual reached the second instar stage, causing pain, lethargy, and minor skin damage. Removal of bot fly larvae requires surgery.

Rabbit bot flies are also known to parasitize domestic rabbits (Oryctolagus cuniculus), with as many as 9 larvae present in a single individual. (Knipling and Brody, 1940; Sabrosky, 1986; Stafford, et al., 2021)

Conservation Status

Rabbit 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 rabbit bot flies.

A threat to this species is forest and pasture fires. Rabbit bot flies are very sensitive to temperature and the change in temperature of the soil causes mortality of eggs, larvae, and pupae. (Colwell, 2001)

Contributors

Dave Brown (author), Radford University, Karen Powers (editor), Radford University, Galen Burrell (editor), Special Projects.

Glossary

Nearctic

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

Neotropical

living in the southern part of the New World. In other words, Central and South America.

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.

carnivore

an animal that mainly eats meat

causes or carries domestic animal disease

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

chemical

uses smells or other chemicals to communicate

diapause

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.

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

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

fertilization

union of egg and spermatozoan

forest

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

fossorial

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

hibernation

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

metamorphosis

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.

monogamous

Having one mate at a time.

motile

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.

oviparous

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

parasite

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

pheromones

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

sanguivore

an animal that mainly eats blood

seasonal breeding

breeding is confined to a particular season

semelparous

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.

sexual

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

solitary

lives alone

tactile

uses touch to communicate

temperate

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).

terrestrial

Living on the ground.

territorial

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

visual

uses sight to communicate

year-round breeding

breeding takes place throughout the year

References

Cameron, A. 1926. The occurrence of Cuterebra (Diptera, Oestridae) in western Canada. Parasitology, 18/4: 430-435.

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

Colwell, D. 2001. Parasitic Diseases of Wild Mammals, Second Edition. Iowa: Iowa State University Press.

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.

GBIF Secretariat, 2022. "Cuturebra buccata" (On-line). GBIF. Accessed June 19, 2022 at https://www.gbif.org/occurrence/search?taxon_key=1587508.

Gingrich, R. 1981. Migratory kinetics of Cuterebra fontinella (Diptera: Cuterebridae) in the white-footed mouse, Peromyscus leucopus. The Journal of Parasitology, 67/3: 398-402.

Hadwen, S. 1915. A description the egg and ovipositor of Cuterebra fontinella, Clark (Cottontail Bot.). Journal of the Entomological Society of British Columbia, N/A: 88-91.

Hunter, D., J. Webster. 2012. AGGREGATION BEHAVIOR OF ADULT CUTEREBRA GRISEA AND C. TENEBROSA (DIPTERA: CUTEREBRIDAE). The Canadian Entomologist, 105/10: 1301-1307.

Jennison, C., L. Rodas, G. Barret. 2006. Cuterebra fontinella parasitism on Peromyscus leucopus and Ochrotomys nuttalli. Southeastern Naturalist, 5/1: 157-167.

Johnson, A., T. Barzee, K. Holbert, S. Poarch, J. Storm. 2018. Effect of Cuterebra fontinella (mouse bot fly) on the movement of Peromyscus leucopus (white-footed mouse). Southeastern Naturalist, 17/4: 597-604.

Kaufman, P., L. Wood. 2015. Discovery and successful development of Cuterebra americana (Diptera: Oestridae) from an atypical host, Rattus rattus (Rodentia: Muridae), in Florida, U.S.A.. Florida Entomologist, 98/1: 349-351.

Knipling, E., A. Brody. 1940. Some taxonomic characters of Cuterebrine (Diptera) larvae, with larval descriptions of two species from Georgia. The Journal of Parasitology, 26/1: 33-43.

Noel, S., N. Tessier, B. Angers, D. Wood, F. Lapointe. 2004. Molecular identification of two species of myiasis-causing Cuterebra by multiplex PCR and RFLP. Medical and Veterinary Entomology, 18/2: 161-166.

Pezzi, M., T. Bonacci, M. Leis. 2019. Myiasis in domestic cats: a global review.. Parasites Vectors, 12: 372.

Sabrosky, C. 1986. North American Species of Cuterebra and Rabbit and Rodent Bot flies.. College Park, Maryland: Entomological Society of America.

Scholl, P. 1991. Gonotrophic development in the rodent bot fly Cuterebra fontinella (Diptera: Oestridae). Journal of Medical Entomology, 28/3: 474-476.

Shiffer, C. 1983. Aggregation behavior of adult Cuterebra fontinella (Diptera: Cuterebridae) in Pennsylvania, USA. Journal of Medical Entomology, 20/4: 365-370.

Slansky, F. 2006. Cuterebra Bot Flies (Diptera: Oestridae) and Their Indigenous Hosts and Potential Hosts in Florida. Florida Entomologist, 89/2: 152-160.

Slansky, F., P. Kaufman, M. Bailey. 2008. First record of Cuterebra fontinella (Diptera: Oestridae) larvae infesting a Florida rat (Rodentia: Muridae). Florida Entomologist, 91/4: 706-708.

Stafford, K., G. Ridge, G. Molaei, C. Zarb, P. Bevilacqua. 2021. Rabbit bot fly furuncular, tracheopulmonary, and human bot fly infestations in Connecticut (Oestridae: Cuterebrinae). Journal of Medical Entomology, 58/1: 114-120.

Wolf, M., G. Batzil. 2001. Increased prevalence of bot flies (Cuterebra fontinella) on white-footed mice (Peromyscus leucopus) near forest edges. Canadian Journal of Zoology, 79/1: 106-109.

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