Black Horsefly
Tabanus atratus
Summary 2
Tabanus is a genus of biting horseflies of the family Tabanidae. Females have scissor-like mouthparts that aim to cut the skin. The horsefly can then lap up the blood. Horseflies of this genus are known to be potential vectors of anthrax, worms and trypanosomes. Some species, such as Tabanus bovinus, prefer bovine animals and are less harmful to humans. The genus contains hundreds of species and many species groups, including:
Distribution 3
Tabanus atratus is primarily found in the eastern United States, although it has been collected throughout the entire continental US.
Biogeographic Regions: nearctic (Native )
Habitat 4
This horsefly is able to survive in a wide range of habitats although it cannot survive in extreme climates such as mountain tops or deserts. It requires moist environments in which to lay eggs, and mammals to feed on.
Terrestrial Biomes: savanna or grassland ; chaparral ; forest
Other Habitat Features: suburban ; agricultural
Life cycle 5
Horse flies pass through the following holometabolous life stages: egg, larva, pupa, and adult. After the eggs hatch, the larvae will drop down into water or burrow into a moist environment where it then matures through six to nine instars before pupation (Hutchinson, 1999). In colder climates, larvae will overwinter, then move to drier soil to in order to pupate (Strother, 2000). The pupal stage lasts from one to three weeks.
Development - Life Cycle: metamorphosis
Morphology 6
Adults of this species reach 20-25 mm in length. The flies can be entirely black, including the wings, or dark brown to blackish purple. Tabanus atratus have large compound eyes, which are dichoptic (separated) in females, and holoptic (continuous) in males. They have prominent mouthparts, which are easily distinguishable: The fascicle is made of six piercing organs. Starting from the outside, there are 2 flattened, bladelike mandibles with tooth like serrations used for cutting. Two narrow maxillae also serrated used to pierce the tissue and blood vessels of the host, a median hypopharynx and a median labrum-epipharynx. The hypopharynx and labrum-epipharynx make up the food canal, while the labrum is a large sponge like organ used to lap up blood (Roberts and Janovy, 2000). Short stout hairs cover the body, and wing venation is pronounced.
Larva of Tabanus atratus are similar to the larvae of all other horseflies. Larvae can be white to tan, while possessing a slender, cylindrical body, which tapers at the head. (Strother, 2000) Like other tabanids, the larva of the black horsefly has twelve segments and a retractable tracheal siphon used for respiration. The retractable head of the larva has two sharp mandibles that can cause a painful bite (Roberts and Janovy, 2000). The pupae have a series of spines sticking out from the abdominal segments, and usually exhibit little movement (Hutchinson, 1999).
Range length: 20 to 25 mm.
Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry
Sexual Dimorphism: sexes shaped differently
Reproduction 7
Tabanus atratus generally breed near aquatic environments. When the adult fly emerges, mating occurs. Females then search for a blood meal, while males feed on nectar.
Each female will lay three to four masses of one hundred to a thousand eggs each, in layers near water's edge or somewhere quite close to water.
Range eggs per season: 300 to 4000.
Key Reproductive Features: iteroparous ; sexual ; fertilization (Internal ); oviparous
After searching for and laying eggs in a suitable environment for larvae to grow and develop, there is no further parental involvement.
Parental Investment: pre-fertilization (Provisioning, Protecting: Female)
Uses 8
Although Tabanus atratus do not often bite humans, when it does happen it leaves painful memories. This fly can also transmit bacterial, viral, and other diseases such as surra and anthrax, to both humans and other animals through its bite.
The effect of T. atratus on livestock can be a serious problem. Blood loss and irritation from the flies can severely affect beef and milk production, as well as grazing. Livestock usually have no way of avoiding the painful bites, and millions of dollars have been spent trying to control these pests.
Negative Impacts: injures humans (bites or stings, causes disease in humans , carries human disease); causes or carries domestic animal disease
Sources and Credits
- (c) Mike Keeling, some rights reserved (CC BY-ND), https://www.flickr.com/photos/pachytime/2813945594/
- Adapted by Allie Hay from a work by (c) Wikipedia, some rights reserved (CC BY-SA), http://en.wikipedia.org/wiki/Tabanus_atratus
- (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/31425577
- (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/31425578
- (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/31425580
- (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/31425579
- (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/31425581
- (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/31425584
