Tabanus lineola

Geographic Range

Tabanus lineola has been found to exist across all of the United Sates and Canada. This species is principally found in coastal regions across eastern and southern United States. Tabanus lineola is present in great density in places such as Ohio, Michigan, Alabama, and South Carolina. This species is also commonly found along the coast of New Jersey and Georgia. (Couvillion, et al., 1986; Joyce and Hansens, 1968; Powder and Loomis, 1962)


Tabanus lineola mostly resides in coastal salt marshes and wetlands. The majority of flies are found 1.5 to 3 feet from the surface of the salt marsh. Tabanus lineola temporarily spends time on its hosts which include humans and several domesticated animals such as horses and hogs. (Joyce and Hansens, 1968; Weiner and Hansens, 1975)

Physical Description

Tabanus lineola is a striped, green-headed horse fly. The length of this species is approximately 12 to 15 mm. Tabanus lineola weighs approximately 50 milligrams and its total volume of blood accounts for about 20% of this mass. They have large, bright green eyes, which usually feature a purple stripe crossing over them. This species has either a black or brown abdomen containing three gray stripes. The appearance of T. lineola may slightly vary between flies living in different habitats. Those found in coastal habitats may be lighter in color with wider frons than those found inland. This species exhibits no sexual dimorphism. (Joyce and Hansens, 1968; Philip and Hamilton, 1942; Schutz, et al., 1989; Schwardt, 1931; Woodring and Leprince, 1992)

  • Sexual Dimorphism
  • sexes alike
  • Average mass
    0.050 g
    0.00 oz
  • Range length
    12 to 15 mm
    0.47 to 0.59 in


Tabanus lineola goes through holometabolous metamorphosis as a means of development. Tabanus lineola always lays its eggs in clusters. The size of the group of eggs may vary but is usually about 10 mm long and 4 mm wide. Each individual egg is approximately 2 mm long and .3 mm thick. The eggs that are first deposited are white in color, but after about a day or so they gradually turn to a dark gray. The eggs remain this color until they hatch. The amount of time for incubation varies based on temperature, but lasts 3 to 5 days on average. The higher the temperature and more intense the sunlight, the faster the eggs will hatch. (Orminati and Hansens, 1947; Richardson and Wilson, 1969; Schwardt, 1931)

The larval period for Tabanus lineola is about 48 days. Tabanus lineola larvae are usually pale white in color, although other colors such as light yellow or pink have been observed. The length of the larval stage is quite short and may only last a month. Larvae reside mostly in the mud of ponds. Tabanus lineola go through 8 to 10 larval stages or instars. The larvae of most Tabanidae will usually molt right after hatching occurs. However, this process has been seen to take a few days in T. lineola. (Orminati and Hansens, 1947; Schwardt, 1931; Whitcomb, et al., 1997)

The pupal period of T. lineola is also brief, ranging from 7 to 16 days. The number of days may lessen in higher temperatures. Pupae are about 11 to 19 mm long and 3 mm wide. After the pupal state, an adult T. lineola emerges from the pupa. Often this emergence occurs in a dry and sandy environment. The total development period of T. lineola, including egg, larval, pupal, and the period before oviposition is approximately 69.9 days. (Orminati and Hansens, 1947; Schwardt, 1931)


The mating mechanism of T. lineola has not often been observed experimentally or in the field so little is known regarding their mating system. (Schwardt, 1931; Wilson, 1967)

After mating, Tabanus lineola females require a blood meal from a vertebrate host in order to oviposit her eggs. Females then need to select a suitable oviposition site, generally on the tips of salt marsh grasses. Tabanus lineola lays an average egg mass size of 208 eggs, which takes approximately 30 minutes to complete. Female flies obtain energy for the oviposition from stored carbohydrates. After several days, spindle-shaped larvae hatch which measure an average 2 mm in length. This species completes 8 to 10 instars. After completing the last instar, larvae will pupate. Pupae average 11 to 19 mm in length. The pupal stage typically lasts from 7 to 16 days, after which a sexually mature adult emerges. (Couvillion, et al., 1986; Orminati and Hansens, 1947; Schwardt, 1931; Wilson, 1967; Woodring and Leprince, 1992)

  • Breeding season
    Tabanus lineola breed in the spring and summer months, which varies geographically.
  • Average eggs per season

There is little available evidence of parental investment for Tabanus lineola.

  • Parental Investment
  • no parental involvement
  • pre-fertilization
    • provisioning
    • protecting
      • female


Under laboratory conditions, female flies may survive 4 or 5 days without a source of carbohydrates. Others, who are provided carbohydrates may survive up to 42 days. (Wilson, 1967)

  • Range lifespan
    Status: captivity
    2 to 42 days


The behavior patterns of Tabanus lineola are greatly influenced by climate patterns. For example, temperature has a large influence on the flight activity of these flies. Higher temperatures and lower cloud cover result in a greater amount of flying activity. The flight activity of male flies is also known to vary with the time of day as well as the season. (Joyce and Hansens, 1968; Richardson and Wilson, 1969)

Home Range

There is little available information about the home range of Tabanus lineola.

Communication and Perception

Tabanus lineola may sense changes in its environment such as variation in temperature and cloud cover. Behaviors and flying activity may change in response to these external changes. For example, a temperature drop will cause flight activity to decline and thus T. lineola are less active in times of cooler temperatures. There is currently little significant research in regards to what sense organs allows these flies to perceive environmental changes or how T. lineola communicates with one another. (Joyce and Hansens, 1968)

Food Habits

Tabanus lineola feeds on both the blood of its hosts as well as plant nectar. Only females feed on blood, which is primarily used for oviposition and the development of eggs. Their digestive systems are unique and are able to store the ingested sugar and blood separately. Adults will feed on blood by cutting through their hosts' skin and suctioning out a blood meal. Common hosts include cattle, horses, mules, and humans. They usually will feed from about 9 a.m. to 6 p.m. Although blood meals are required for successful reproduction, females who cannot obtain blood meals may still live just as long as those who do. Therefore, is can be assumed that carbohydrates are what keeps T. lineola alive rather than nutrients in blood. (Whitcomb, et al., 1997; Wilson, 1967; Woodring and Leprince, 1992)

When reared in captivity, larvae are known to feed on various foods. They appear to prefer snails, worms, and the abdomen of crustaceans. However, when larvae are about to transform between instars during development, they experience a time of complete rest where the will refuse any food. (Schwardt, 1931)

  • Animal Foods
  • blood
  • mollusks
  • terrestrial worms
  • aquatic crustaceans
  • Plant Foods
  • nectar


There is little available information regarding the predators of Tabanus lineola. Larvae are very vulnerable, and are likely consumed by many insectivorous organisms including birds, amphibians, reptiles, mammals, and other insects. Adult flies are likely predated by birds and possibly predatory wasps. Tabanus lineola egg masses are known to be eaten by seriate lady beetles. (Orminati and Hansens, 1947)

Ecosystem Roles

This species acts as a parasite to both domesticated animals, such as hogs, horses, and mules, as well as humans. At every stage of its life, Tabanus lineola serves as prey to a wide variety of other organisms. Adults of this species are also potential pollinators for local plants, due to their mainly nectivorous diet. (Magnarelli, et al., 1986; Orminati and Hansens, 1947; Weiner and Hansens, 1975)

In addition to acting as a parasite, there has also been occurrences of Tabanus lineola being the infected host for the larvae of arterial worms (Elaeophora schneideri). Although third stage larvae of this species have been found to infect T. lineola, the prevalence is quite low. Tabanus lineola are also hosts for bacteria of the genus Spiroplasma. They most likely acquire these bacteria through their environment as it is passed to other flies at common feeding sites that contain carbohydrates like honeydew or tree sap. This association may allow humans to control T. lineola populations using spiroplasmas. (Couvillion, et al., 1986; French, et al., 1997; Wedincamp, et al., 1997; Whitcomb, et al., 1997)

Species Used as Host
  • domestic horses (Equus ferus caballus)
  • domestic pigs (Sus scrofa domesticus)
  • mules
  • humans (Homo sapiens)
Commensal/Parasitic Species
  • bacteria (Spiroplasma)
  • aterial worms (Elaeophora schneideri)

Economic Importance for Humans: Positive

Tabanus lineola does not appear to have any beneficial effects on humans.

Economic Importance for Humans: Negative

Tabanus lineola is a major annoyance to domesticated animals being that they suck their blood for nutrients. This causes a decrease in livestock production because the animals may experience irritation, a large loss of blood, and exposure to diseases vectored by T. lineola. Humans must try to methodically control these pest populations so that livestock production is not affected. There have been efforts to prevent T. lineola from harming domesticated animals through the use of insecticides, such as fenvalerate. Although some T. lineola are unharmed by these efforts, many are killed or unable to feed on enough blood. Many flies have built up a resistance to these insecticides so they may no longer be effective. An alternative possibility in controlling these pest populations is to infect them with spiroplasmas. (Foil, et al., 1991; Weiner and Hansens, 1975)

Conservation Status

Tabanus lineola is found across a broad distribution and is especially common in the eastern parts of North America. This species appears to be fairly easy to capture for experimental purposes due to their abundant presence. Being that they are so common, they do not appear to be at any risk of endangerment. There are currently no conservation efforts because of the negative impact this pest has on humans and domesticated animals. (Powder and Loomis, 1962; Schwardt, 1931)


Diana Kaplan (author), University of Michigan-Ann Arbor, Heidi Liere (editor), University of Michigan-Ann Arbor, John Marino (editor), University of Michigan-Ann Arbor, Barry OConnor (editor), University of Michigan-Ann Arbor, Rachelle Sterling (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.

causes or carries domestic animal disease

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


the nearshore aquatic habitats near a coast, or shoreline.


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


union of egg and spermatozoan


An animal that eats mainly plants or parts of plants.


marshes are wetland areas often dominated by grasses and reeds.


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 the capacity to move from one place to another.


an animal that mainly eats nectar from flowers


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

saltwater or marine

mainly lives in oceans, seas, or other bodies of salt water.

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


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.



Foil, L., D. Leprince, R. Byford. 1991. Survival and Dispersal of Horse Flies (Diptera: Tabanidae) Feeding on Cattle Sprayed with a Sublethal Dose of Fenvalerate. Journal of Medical Entomology, 28: 663-667.

French, F., R. Whitcomb, J. Tully, P. Carle, J. Bove, R. Henegar, J. Adams, G. Gasparich, D. Williamson. 1997. Spiroplasma lineolae sp. nov., from the Horsefly Tabanus Lineola (Diptera: Tabanidae). International Journal of Systematic Bacteriology, 47/4: 1078-1081.

Joyce, J., E. Hansens. 1968. The Influence of Weather on the Activity and Behivor of Greenhead Flies, Tabanus nigrovittatus Macquart and Tabans lineola Fabricius. Journal of the New York Entomological Society, 76: 72-80.

Magnarelli, L., J. Anderson, A. Barbour. 1986. The Etiologic Agent of Lyme Disease in Deer Flies, Horse Flies, and Mosquitoes. The Journal of Infectious Diseases, 154/2: 355-358.

Orminati, S., E. Hansens. 1947. The Biology of Tabanus lineola lineola F.. Entomological Society of America, 67/6: 937-939.

Philip, C., M. Hamilton. 1942. Notes on Nearctic Tabaninae. Part III. THE TABANUS LINEOLA COMPLEX. Psyche, 48: 25-29.

Powder, W., R. Loomis. 1962. A New Species and New Records of Chiggers (Acarina, Trombiculidae) from Reptiles of Southern California. The Journal of Parasitology, 48: 204-208.

Richardson, C., B. Wilson. 1969. Daily Flight Activity of Male *Tabanus lineola* var. *Hinellus*Philip (Diptera: Tabanidae) in the Estuarine Area of Louisiana. Journal of Medical Entomology, 6/3: 276-277.

Schutz, S., R. Gaugler, E. Vrijenjoek. 1989. Genetic and Morphometric Discrimination of Coastal and Inland Tabanus lineola (Diptera, Tabanidae). Annals of the Entomological Society of America, 82: 220-224.

Schwardt, H. 1931. THE BIOLOGY OF TABANUS LINEOLA FABR.. Annals of the Entomological Society of America, 24/2: 409-416.

Wedincamp, J., F. French, R. Whitcomb, R. Henegar. 1997. Laboratory Infection and Release of Spiroplasma (Entomoplasmatales: Spiroplasmataceae) from Horse Flies (Diptera: Tabanidae). Journal of Entomological Science, 32/4: 398-402.

Weiner, T., E. Hansens. 1975. Species and Numbers of Bloodsucking Flies Feeding on Hogs and Other Animals in Southern New Jersey. Journal of the New York Entomological Society, 83: 198-202.

Whitcomb, R., F. French, J. Tully, P. Carle, R. Henegar, K. Hackett, G. Gasparich, D. Williamson. 1997. Spiroplasma Species, Groups, and Subgroups from North American Tabanidae. Current Microbiology, 35: 287-293.

Wilson, B. 1967. Feeding Mating and Oviposition Studies of Horse Flies Tabanus lineola and T. fuscicostatus (Diptera:Tabanidae). Annals of the Entomological Society of America, 60: 1102.

Woodring, J., D. Leprince. 1992. The Function of Corpus Cardiacum Peptides in Horse Flies. J. Insect Physiol., 38: 775-782.