Culicoides variipennis

Geographic Range

Culicoides variipennis is found throughout North America, wherever large mammal hosts (especially ruminants) are available.

• Biogeographic Regions
• nearctic nearctic
  • native native

Habitat

Culicoides variipennis is found mainly in moist areas and low wetlands, so livestock and animals attempting to avoid this parasite are best able to do so by staying in higher and dryer areas.

• Habitat Regions
• freshwater freshwater

• Terrestrial Biomes
• savanna or grassland savanna or grassland
• forest forest

• Aquatic Biomes
• lakes and ponds
• rivers and streams
• temporary pools

• Wetlands
• marsh marsh
• swamp swamp

• Other Habitat Features
• agricultural agricultural
• riparian riparian

Physical Description

Adult Culicoides variipennis are less than 1 mm in length, allowing them to be very pesky and difficult to keep from livestock. The genus can also be identified by its spotted, narrow wings. These wings also have few veins and fold over the abdomen while the fly is at rest. Only females feed on blood, so they have somewhat different mouthparts from males.

• Other Physical Features
• ectothermic ectothermic
• heterothermic heterothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• sexes alike

Reproduction

Females of this species lay their eggs in wet environments, including aquatic, subaquatic, or moist soil conditions, where they hatch and develop into larvae. These aquatic or subaquatic larvae feed on dying organisms or other organic material. Depending on the environmental conditions, the life cycle may last a half year up through three years.

• Key Reproductive Features
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• fertilization fertilization
  • internal internal
• oviparous oviparous

Behavior

Culicoides variipennis tends to be a swarming insect; it usually attacks its host in swarms. The slight size of the insect makes it difficult for the host to rid itself of the pest, so the fly can attack the host in great numbers.

• Key Behaviors
• flies
• parasite parasite
• motile motile

Food Habits

This dipteran feeds on a variety of domestic ruminants, most notably sheep and cattle , along with some wild ruminants. Culicoides variipennis lands on its host, where it bites through the skin. The species is a telmophage, which means it bites through the skin and laps up the blood that pools out. Culicoides variipennis bites the host with its mandibles and feeds on the blood with its proboscis.

• Primary Diet
• carnivore carnivore
  • sanguivore sanguivore
• detritivore detritivore

• Animal Foods
• blood
• body fluids

• Other Foods
• detritus detritus

Ecosystem Roles

These insects are food for a variety of small predators, mostly other insects and spiders. Females of this species feeds on a variety of ruminant mammals, most notably sheep and cattle , along with some wild ruminants. They are also a vector for the virus that causes "bluetongue," a disease in domestic livestock.

This species is also host to a parasitic nematode, Heleidomermis magnapapula .

Economic Importance for Humans: Negative

Culicoides variipennis has a negative impact on the agricultural economy. The flies themselves aren't very harmful to livestock, but they are a vector to a more prominent problem: the virus that causes "bluetongue." Infection by the bluetongue virus can cause a variety of symptoms in ruminants, such as swelling of the tongue and face and erosions in the mouth and throat. The symptoms are less severe in cattle, but infection in sheep often leads to death. Also, infection in pregnant ruminants can lead to adverse effects--central nervous system damage and death--to developing fetuses if the infections occur early enough in the pregnancy. In addition, it is estimated that in the late 1990's, about $125 million was lost annually in the agricultural economy because of export restrictions intended to prevent bluetongue-infected livestock from being shipped to bluetongue-free countries.

The virus is easily transferrable from fly to host and vice versa via C. variipennis feeding on host blood. The virus can replicate in the fly's thorax, and can eventually be secreted in the fly's saliva within 7-10 days, when it can be transferred to another ruminant.

• Negative Impacts
• causes or carries domestic animal disease causes or carries domestic animal disease

Conservation Status

This species is quite common and has no special conservation status.

Other Comments

There is a natural parasite that is being manipulated to combat C. variipennis , the nematode Heleidomermis magnapapula . Studies are currently being conducted to test the effectiveness of this hyperparasite (an organism that parasitizes another parasite).

Additional Links

Encyclopedia of Life

Contributors

Renee Sherman Mulcrone (editor).

Nathan Lenneman (author), University of Michigan-Ann Arbor, Barry OConnor (editor), University of Michigan-Ann Arbor.

References

Anderson, N. 2000. Plain talk on sheep health. Suffolk News , July/August 2000.

Bowne, J., R. Jones. 1966. Observations on bluetongue virus in the salivary glands of an insect vector, Culicoides variipennis. Virology , 30: 127-133.

Kimberling, C. 1988. Diseases of sheep, 3rd ed. . Philadelphia: Lea and Febiger.

Paine, E., B. Mullens. 1994. Distribution, seasonal occurrence, and patterns of parasitism of Heleidomermis magnapapula (Nematoda: Mermithidae), a parasite of Culicoides variipennis (Diptera: Ceratopogonidae) in California. Environmental Entomology , 23: 154-160.

Roberts, L., J. Janovy. 2000. Foundations of Parasitology, 6th ed. . Boston: The McGraw-Hill Companies, Inc..

Tabachnick, W. 1996. Culicoides variipennis and bluetongue virus epidemiology in the United States. Annual Review of Entomology , 41: 23-43.