Blood engorged no-see-um biting a human  - click on photo to enlarge
Coping with No-See-Ums - September 21, 2005
Jeff Schalau, Associate Agent, Agriculture & Natural Resources
University of Arizona Cooperative Extension, Yavapai County

No-see-ums are small biting flies that appear during the summer months. These tiny biting insects are barely visible to the naked eye, but their bites can be very painful and annoying. Also known as biting midges or punkies, these minute insects are probably familiar to outdoor enthusiasts, gardeners, farmers, and ranchers. Each year, I get several calls from residents that think they have flea bites or chiggers, but after speaking to them, we usually find they have been bitten by no-see-ums.

Literature references indicate that no-see-um species found in Arizona and the southwest are of the genus Culicoides (family Ceratopogonidae). Adult no-see-ums are less than 1/16-inch long (see photo above), can easily pass through normal window screens, and resemble a smaller, more compact version of the mosquito. They are most active in early mornings and evenings of mid to late summer. Mouth parts are well developed with elongated mandibles adapted for blood sucking. Both males and females feed on flower nectar but only the female feeds on blood. She must consume blood for her eggs to mature and become viable.

No-see-um eggs are laid on moist soil. Common breeding areas include the edges of springs, streams and ponds, muddy and swampy areas, tree holes, and even water associated with air conditioning units. University of Arizona Entomologist, Carl Olson, says they also breed in moist disturbed soil such as that found around construction sites or freshly plowed ground. The eggs hatch in as little as 3 days. The wormlike larvae have short brush like breathing structures that allows them to breathe in an aquatic environment. Although larvae are not strictly aquatic or terrestrial, they can not develop without moisture. After feeding on decomposing organic matter and pupating, adults emerge, feed, and mate.

As mentioned previously, bites of these tiny flies are painful and irritating. The bite usually starts as a small red welt (1/8Ē or so) or water-filled blister that itches. Once scratched, the welt can break open and bleed, but the itching usually continues. Allergic or sensitive individuals may develop long-lasting painful and itchy lesions. Bite treatments recommended by some dermatologists include topical cortisone creams and non-steroidal anti-inflammatory drugs such as aspirin or ibuprofen. Persons having severe reactions should consult a physician or dermatologist.

Insect repellents containing DEET typically used against mosquitoes are also labeled for use against biting midges. Always follow the label precautions and apply before exposure to the insects. Botanical insect repellents (those containing citronella, eucalyptus, and other plant extracts) may also provide some protection. Occasionally no-see-ums and biting midges will enter houses and screened patios through standard 16 mesh screening and netting or damaged areas of the screen. If this is the case you can replace damaged screen with tighter mesh screen or treat existing screen with an approved insecticide such permethrin.

The best strategy to prevent no-see-um bites is to wear long sleeve shirts, long pants, shoes and socks, and a hat during times when no-see-ums are most active. No-see-um-proof netting is also available and outdoor equipment companies market head nets, jackets, and pants made from this material. These products may come in handy depending on your preferences and outdoor activity preferences. While I donít own one, the head net seems like an excellent idea. Of course, these same strategies are also effective against mosquitoes and black flies.

No-see-ums do not spread West Nile virus (WNV) and only mosquitoes can vector this disease. However, in case you were wondering, the number of documented human cases of WNV infection in Arizona is 29 for the summer of 2005 (as of September 13). Only one of these was in Yavapai County. As some readers are probably aware, this is a significant decrease from last yearís 391 documented cases. Regardless, WNV will be with us for the foreseeable future and we should all continue to be aware and take precautions.

The University of Arizona Cooperative Extension has publications and information on gardening and pest control. If you have other gardening questions, call the Master Gardener line in the Cottonwood office at 646-9113 ext. 14 or E-mail us at and be sure to include your address and phone number. Find past Backyard Gardener columns or submit column ideas at the Backyard Gardener web site:

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Arizona Cooperative Extension
Yavapai County
840 Rodeo Dr. #C
Prescott, AZ 86305
(928) 445-6590
Last Updated: July 13, 2011
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