Chrysops atlanticus

Geographic Range

Saltmarsh deer flies inhabit a range that is restricted to North America. They are commonly found along the eastern coast of the United States from Massachusetts to Florida. Specifically, they are most prevalent in the Carolinas; however, they can be found as far west as Mississippi. Their northern ranges are restricted to coastal areas because they are the only areas that offer the appropriate breeding habitats. These breeding habitats have supported isolated populations as far north as Maine. (Orihel and Lowrie, 1975; Thompson, 1967)


Chrysops atlanticus breeds in marshlands and swamps. However, some studies show that the adult form is most active in the upland regions that border on marshes. They are known to infest beaches, campgrounds, rivers, and swamps. Chrysops atlanticus shows a preference for areas in excess of 30 degrees Celsius. (Dale and Axtell, 1975; Hansens and Robinson, 1973; Hansens, 1979)

Physical Description

Female Chrysops atlanticus are characterized as having deep yellow antennae and a yellow-brown proboscis that fades to dark brown from the head. It has a dark brown area separating its two ocelli, and a narrow deep depression that runs between the antennae. The thorax of female C. atlanticus has three black stripes, the middle stripe being much narrower than the outer two. The legs are mostly yellow, while the halteres are yellow-brown. The wings of C. atlanticus are smokey in color. The abdomen of C. atlanticus is described as a brownish-yellow and is separated into a series of yellowish sternites and tergites. The 5th tergite has four black spots along the anterior margin of the segment, and the 6th tergite has a black band in that same position. The 4th and higher sternites are slightly more dusky in color.

Male C. atlanticus vary only slightly from females. The hairs on the antennae are finer and longer than the females. The dorsal stripes on the thorax are less obvious. Generally the abdomen is a slightly deeper shade of brownish yellow than the female. The 5th and 6th tergites are largely black, which differs from the banded and spotted pattern observed on females. This is also true of the deeper shaded 4th and higher sternites. Both males and females range in length from 6.5 to 9.5 mm. (Pechumen, 1949)

  • Sexual Dimorphism
  • sexes colored or patterned differently
  • Range length
    6.5 to 9.5 mm
    0.26 to 0.37 in


Adult Chrysops atlanticus develop seasonally from approximately May 19th to August 14th. Larvae hatch within 5 to 7 days of oviposition and grow at approximately 4 mm per month, depending on the availability of nutrients. The larvae are termed "hydrobionts", which means that they are found in areas of high water content (eggs are typically deposited above freshwater marsh water). The larvae pass through six to nine stadia in 1 to 12 months and then pupate. The adults emerge two to three weeks later and live for only 30 to 60 days. (Meany, et al., 1976; Squitier, 2007; Thompson, 1967)


All members of the genus Chrysops are polygynous, but little is known regarding how potential mates are located or selected. (Squitier, 2007)

Development of egg follicles within adult Crysops atlanticus females requires 10 days. Therefore, females are sexually mature after 10 days of becoming adults. Though the length can vary slightly depending on the amount of blood meals and nutrients available to the female. Females lay an average of 147.5 eggs per deposition in late June and early July. Eggs are arranged in a single layer, often in the curvature of blades of grass in and around freshwater marsh flats. On average, 78% of these eggs will hatch in 7 days, the remainder never fully develop.

Chrysops atlanticus exhibits egg production without a blood meal for the first gonotrophic cycle but any ovarian cycles after that require vertebrate blood for gestation. It is unknown if adult females require plant sugars for egg production. Some scientists suggest that the presence of sucrose has little or no effect on the initial ovarian cycle. (Magnarelli and Anderson, 1977; Magnarelli and Anderson, 1979; Thompson, 1967)

  • Breeding interval
    Chrysops atlanticus breeds multiple times a year under favorable habitat conditions.
  • Breeding season
    Chrysops atlanticus breeds from approximately mid-May through mid-August
  • Average gestation period
    7 days
  • Average age at sexual or reproductive maturity (female)
    10 days

After mating and egg deposition, Chrysops atlanticus shows no parental investment for its young. (Squitier, 2007)

  • Parental Investment
  • no parental involvement


Little is known about Chrysops atlanticus in regards to its maximum and minimum lifespan; though they are estimated to live 30 to 60 days in the wild. Likely factors that affect lifespan include climatic conditions and predation. (Hansens, 1979)

  • Typical lifespan
    Status: wild
    30 to 60 days


Chrysops atlanticus shows an attraction to the chemical 1-octen-3-ol. This is important in studying the fly because most of the information about habitat has been collected by trapping the fly. Trapping has been used to control the number of insects in livestock areas. Traps designed to catch the flies are usually dark, or blue in color and are suspended at least .6 meters above the ground. DEET tends to be the most effective repellent of these flies. These flies are most active when light levels are approximately 5000 lux, therefore they prefer to fly on overcast days, and early or late in the day. (French and Hagan, 1998; Hansens, 1979)

Home Range

The exact territory size of saltmarsh deer flies is unknown, however they can travel hundreds of yards from where they developed into adults. Open fields and windy conditions increase the distance it can travel.

Communication and Perception

Chrysops atlanticus males use visual detection as a means to find mates. During peak hours of activity, males hover and when they detect other flying insects, dart after them. They, like most members of the Tabanidae family, show an attraction to dark colors as opposed to light and are often trapped using visual traps and decoys. Visual traps show more effectiveness if animal baits or carbon dioxide is used in the trap. Experimental results based on this conclude that Chrysops species identify potential hosts by in-flight detection of carbon dioxide gradients, and then use vision as a secondary means of identification. (Allan, et al., 1987)

Food Habits

Male Chrysops atlanticus feed exclusively on nectar and other plant sugars. For most of their lives, females survive mainly plant nutrients as well. Females only require a blood meal to lay their eggs. However, females that overwinter will lay their first brood after awakening in the spring without a blood meal. All subsequent batches require females to locate and feed from a vertebrate host. Females tend to feed on or around the head and arms and are attracted to movement when feeding. Blood feeding can range from 40 to 200 mg of blood per fly per day. Larvae survive by feeding on organic detritus, but occasionally exhibit cannibalism. (Hansens, 1979; Squitier, 2007)

  • Animal Foods
  • blood
  • Plant Foods
  • nectar
  • pollen


Chrysops atlanticus are subjected to predation at all life stages. Ladybird beetle larvae prey on eggs, wading birds feed on larvae, and dragonflies and certain solitary wasps attack adults. Some wasps have developed to parasitize Tabanidae eggs. There are also some fungal, bacterial, and protozoan pathogens that have been known to threaten members of the Tabanidae family. (Mullen and Durden, 2009)

Ecosystem Roles

Chrysops atlanticus functions as an important parasite of humans, livestock, and other vertebrates. Members of the Chrysops genus are known vectors for disease including filarial nematodes known as Loa loa that infects human eyes. The larval, pupae and adult forms of this species are preyed upon by many other organisms, and thus they likely support local predator populations. (Eberhard and Orihel, 1981; Hansens, 1979)

Species Used as Host

Economic Importance for Humans: Positive

There is a possibility that Chrysops atlanticus contributes positively to pollination of some crops, however more research is needed to prove this.

Economic Importance for Humans: Negative

Tabanidae flies have been known to transmit bovine anaplasmosis, anthrax, hog cholera, equine infection anemia, and other livestock diseases in tropical areas of the world. They are suspected of transmitting vesicular stomiasis, though this has yet to be proved. Aside from disease transmission, Chrysops atlanticus can have a huge negative impact on the health of domesticated animals. It is estimated that forty to fifty flies can can remove one-third of a quart of blood from an animal every day. This has effects on livestock weight gains and milk production. When this species is active it has been known to move from marshes to nearby golf courses, campgrounds, and beaches in search of human blood meals. This often discourages business at outdoor recreation establishments. Females' saliva contains an anti-coagulant that serves to keep a wound open while flies feed. Hosts that have been bitten often experience redness and itching around the bite as a reaction to the saliva. A small portion of the population however, will show a allergic reaction to the bites and will experience significant swelling, rarely requiring hospitalization. (Frost and Pechuman, 1958; Hansens, 1979)

Conservation Status

Any efforts to affect populations of saltmarsh deer flies are to reduce their numbers. They are significant vectors for both human and domestic animal diseases, and several methods are in place to control their population to curb disease transmission. Thus, this species is currently of no conservation concern.


Jordan LaFave (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


uses smells or other chemicals to communicate


active at dawn and dusk


particles of organic material from dead and decomposing organisms. Detritus is the result of the activity of decomposers (organisms that decompose organic material).


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.

internal fertilization

fertilization takes place within the female's body


offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).


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.

native range

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


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

polarized light

light waves that are oriented in particular direction. For example, light reflected off of water has waves vibrating horizontally. Some animals, such as bees, can detect which way light is polarized and use that information. People cannot, unless they use special equipment.


having more than one female as a mate at one time

seasonal breeding

breeding is confined to a particular season


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


a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.


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.


the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.


uses sight to communicate


Allan, S., J. Day, J. Edman. 1987. Visual Ecology of Biting Flies. Annual Review of Entomology, 22: 297-314.

Dale, W., R. Axtell. 1975. Flight of the Salt Marsh Tabanidae (DIPTERA), Tabanus Nigrovittatus, Chrysops Atlanticus and C. Fuliginosus: Correlation With Temperature, Light, Moisture and Wind Velocity. Journal of Medical Entomology, 12: 551-557.

Eberhard, M., T. Orihel. 1981. Development and Larval Morphology of Loa loa in Experimental Primate Hosts. The Journal of Parasitology, 67: 556-564.

French, F., D. Hagan. 1998. Two-tier box trap catches Chrysops atlanticus and C. fuliginosus (Diptera: Tabanidae) near a Georgia salt marsh.. Journal of Medical Entomology, 32: 197-200. Accessed April 02, 2010 at

Frost, S., L. Pechuman. 1958. The Tabanidae of Pennsylvania. Transactions of the American Entomological Society, 84: 169-215.

Hansens, E., J. Rabin. 1981. Deer Fly, Chrysops-Atlanticus Pechuman (Diptera, Tabanidae), Activity in Cultivated Fields and Nearby Salt-Marsh Breeding Places. Environmental Entomology, 10: 590-592.

Hansens, E., J. Robinson. 1973. Emergence and Movement of Saltmarsh Deer Flies Chrysops-Fulignosis and Chrysops-Atlanticus. Annals of the Entomological Society of America, 66/6: 1215-1218.

Hansens, E. 1979. Review: Tabanidae of the East Coast as an Economic Problem. Journal of the New York Entomological Society, 87: 312-318.

Magnarelli, L., J. Anderson. 1977. Follicular Devlopment in Salt Marsh tabanidae (Diptera) and Incidence of Nectar Feedin with Relation to Gonotrophic Activity. Annals of the Entomological Society of America, 70: 529-533.

Magnarelli, L., J. Anderson. 1979. Oviposition, Fecundity, and Fertility of the Salt-Marsh Deer Fly, Chrysops-Fulignosis (Diptera-Tabanidae). Journal of Medical Entomology, 15: 176-179.

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: 355-358.

Meany, R., I. Valiela, J. Teal. 1976. Growth, Abundance and Distribution of Larval Tabanids in Experimentally Fertilized Plots on a Massachusetts Salt Marsh. Journal of Applied Ecology, 13: 323-332.

Mullen, G., L. Durden. 2009. Medical Veterinary Entomology. Burlington, MA: Academic Press. Accessed April 02, 2010 at

Orihel, T., R. Lowrie. 1975. Loa loa: development to the infective stage in an American deerfly, Chrysops atlanticus.. The American Journal of Tropical Medicine and Hygiene, 24: 610-615.

Pechumen, L. 1949. Sone Notes on the Tabanidae (Diptera) and the description of two new Chrysops. The Canadian Entomologist, 81/4: 77-82.

Sofield, R., R. Gaugler. 1984. Oviposition Behavior of Chrysops atlanticus (Diptera: Tabanidae). Journal of the New York Entomological Society, 92: 403-404.

Squitier, J. 2007. "Deer Flies, Yellow Flies and Horse Flies, Chrysops, Diachlorus, and Tabanus spp. (Insecta: Diptera: Tabanidae)" (On-line pdf). Accessed March 23, 2010 at

Thompson, P. 1967. Tabanidae of Maryland. Transactions of the American Entomological Society, 93: 463-519.

Uebel, E., W. Bickley. 1976. Tabanidae (Diptera) at Selected Sites in Maryland. Proceedings of the Entomological Society of Washington, 78: 176-180.