Biting Midges (Culicoides)

Posted in   General   on  March 17, 2021 by  Midge Education0

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Engaging in outdoor activities such as camping, hiking, fishing, and lounging on the beach can be refreshing. However, many will attest that biting midges can render these otherwise beautiful occasions uncomfortable and distasteful because of their nasty bites. These biting flies are encountered at least once in a person’s lifetime.  

Still, not many people know much about biting midges, and why learning about them can be beneficial to deal with them.

What exactly are biting midges? How do they behave? Why should people care to know about these biting flies?

What are Biting Midges?

Biting midges belong to the Ceratopogonidae family, along with over 5600 other species. They are of the genus Culicoides and are minuscule, winged insects.While “biting midge” is a common name for these insects, their geographical location is used to identify them.  In some areas, biting midges are nicknamed “no-see-ums”, “sandflies” “punkies”, among others.

Over 1400 species of Culicoides exist.

Belonging to the order Diptera, biting midges exhibit the order’s defining characteristics: a single pair of wings, a separate, mobile head on which sit large compound eyes, and mouthparts optimized for piercing and sucking.

They are found in shades of gray, black, and brown, but may also appear red or dark orange when filled with blood. This, along with their darkly patterned wings, makes it easy to mistake them for mosquitoes. However, biting midges lack the long, tubular proboscis that mosquitoes have for piercing and sucking.  Also, they are much smaller than mosquitos at only 1-3mm in length—roughly the size of a pinhead—making them some of the smallest ceratopogonids, hence the previously-mentioned nickname, “no-see-ums.”

Biting VS Non-Biting Midges

Another insect that is confused for both the mosquito and biting midge is the NON-biting midge. This common name can be somewhat misleading because although they belong to the same order (Diptera) as biting midges and are therefore closely related, non-biting midges comprise another family altogether: Chironomidae. Like biting midges, though, they are also known by many other common names, depending on location: “lake flies” in Canada, “Canadian soldiers” in The Great Lakes area, and “blind mosquitoes” in Florida.

The most significant (and perhaps most obvious) distinction between the two is that biting midges rely on vertebrates’ blood both for energy and reproduction, while non-biting midges do not. As larvae, non-biting midges subsist on organic material, and as adults, they require little nourishment. They hardly eat, scavenging small amounts of nectar, pollen, and other sugar-rich materials.

Considering this, one physical feature that sets non-biting and biting midges apart is the smaller mouthparts lacking piercing structures in the former. Other physical differences include the absence of wing scales and longer forelegs in non-biting midges.

Unlike the biting midges, non-biting midges are mostly harmless, albeit fairly annoying, especially in swarms.

The Biting Midge Life Cycle

The biting midge is a holometabolous insect. It undergoes complete metamorphosis, with a life cycle that involves four stages: egg, larva, pupa, and adult.

Except for a few species that can use their larval reserves to produce viable eggs, female biting midges generally require a blood meal for eggs to mature. The number of 0.25-mm cylindrical, elongated eggs may range from 30-200 per batch, depending in part on the amount of blood ingested by the female.

Depending on the temperature, biting midge eggs hatch larvae in 2-10 days. Upon hatching, the larvae move down through the substrate surface partly to avoid predators such as birds, commonly occupying the top 2 cm of soil.

After 14 days in warmer areas to as long as 9 months in cooler climes such as Scotland, larvae grow into pupae about 1-3mm long. While these pupae are roughly the size of the adult biting midge, they still lack the complete physical features of the full-grown insect. This pupal period lasts for 2-10 days, in which the wings, legs, and antennae are developed, and the pupae grow into adult biting midges.

Adult biting midges have lifespans of 2-7 weeks, and usually complete two or more succeeding generations per calendar year.

Food and Habitat of Biting Midges

Being a family of a diverse species, biting midges can be found nearly anywhere, regardless of climate or conditions throughout the world. However, they are not found in the frigid zones. They are neither strictly aquatic nor terrestrial. Freshwater bodies, as well as marshes or even tree debris and wastewater seepage alike, can give rise to biting midge larvae. Given this diversity of habitat, biting midge larvae are omnivores or detritus feeders, feeding on algae and/or soil nematodes.

For their own metabolic needs, mature biting midges rely mostly on plant sap and nectar. Egg production, on the other hand, requires protein that female biting midges then obtain from either body fluids of small insects, or vertebrate blood. As blood is primarily required for yielding eggs, males do not bite. 

While mammals are their primary hosts, birds, reptiles, and amphibians may also be secondary blood sources. Some species of biting midges prefer a particular host and seek out certain animals to target, but many are opportunistic feeders. These opportunistic species are lured by animals close in proximity through carbon dioxide emissions.

Why Is It Important to Learn More About Biting Midges?

At least 50 vector-borne diseases can be linked back to biting midges. They are effective vectors of diseases; female biting midges, in particular, have been observed to travel several miles in search of hosts, and this area of dispersion can be further augmented by wind.

For humans, midge bites are normally annoying at worst, causing temporary burning, itching, and slight swelling. However, some cases may lead to more intense reactions, that may call for a hospital visitation. Scarring could result from bites.  In Central and South America, parts of Africa, and some Caribbean islands, biting midges are also vectors of filarial worms, a parasite that can cause skin lesions and infections in humans.

The effect of biting midges on livestock is much more dangerous (and commercially costly). They carry a variety of diseases that affect entire herds of cattle, sheep, and deer, reducing milk yields, and causing sterility, abortion, and hemorrhages that may ultimately lead to death.

Additional References:

Hill, C. A., & MacDonald, J. F. (2010, May). Biting Midges: Biology and Public Health Risk. Purdue University Public Health Department of Entomology.

https://extension.entm.purdue.edu/publichealth/insects/bitingmidge.html

Connelly, C. R. (2019, June). Biting midges, no-see-ums, Culicoides spp. University of Florida Entomology and Nematology Department Featured Creatures.

http://entnemdept.ufl.edu/creatures/aquatic/biting_midges.htm#ref

Sick, F., Beer, M., Kampen, H., & Wernike, K. (2019). Culicoides Biting Midges—Underestimated Vectors for Arboviruses of Public Health and Veterinary Importance. Viruses, 11(4), 376.

https://doi.org/10.3390/v11040376

Image Credit:

Image #1: Joseph Berger, Bugwood.org
Creative Commons License   licensed under a Creative Commons Attribution 3.0 License.

IMAGE DESCRIPTION: Midge Chironomus decorus adult

Featured Image & Image 2: Scott Bauer, USDA Agricultural Research Service, Bugwood.org
Creative Commons License   licensed under a Creative Commons Attribution 3.0 License.

IMAGE DESCRIPTION: A sixteenth-inch-long female biting midge, Culicoides sonorensis, feeds blood delivered through artificial membrane developed for mass insect rearing.

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