Aggieland’s Biting Flies!! It sounds like a horror film headline, but it’s true. The cities of Bryan and College Station have a history of biting flies, especially black flies. The black flies are small, gnat-sized terrors that make mosquitoes seem peaceful. Whereas mosquitoes tend to bite in the early and later parts of the days, black flies attack residents of Bryan, College Station, and Central Texas throughout the entire day.
The Bite of the Black Fly
These flies leave a painful bite. They are blood eaters, and their mouths are designed to puncture quickly so that they can feed rapidly and be gone before you slap at them. The mouth part of the black fly consists of two serrated mandibles that they jab into your flesh, spread apart and then rip out of you. While they stab you, they are pumping in an anticoagulant and already feeding. Their mandibles sever many capillaries and small veins so that you bleed quickly.
The bites of the black fly are painful, then the swelling sets in, and the bites begin to itch.  It is the anticoagulant that causes the pain, itching, and swelling. There are many species of black fly, and around the world, they are known to spread disease. The primary disease that they spread is called River Blindness, and it is caused by a worm that the fly carries.  When the female black fly bites, she can ingest the worm from someone who is infected and then transmit that worm into another person. The female worm can produce thousands of new larvae every day. The worms encapsulate themselves and do not always set off an immune response. They eventually make their way into the eye where they cause blindness. If the infection is caught quickly, treatment can reverse vision issues.
Are Black Flies Dangerous to Texans?
Beyond the risk of secondary skin infections from their bite, they are not normally dangerous to Texans. River Blindness is a disease of Africa and the Middle East, though it is possible that an outbreak could occur in the US, it is not very likely, and no cases have been reported to the CDC that were transmitted here. There have been outbreaks in Mexico, Central and South Americas. As of the writing of this article, no information was available to see if the domestic species of black fly can carry the pathogens that cause River Blindness. As a hypothesis, it seems possible that domestic black flies could harbor that potential danger. There have been studies that show that the domestic mosquito can carry the Zika virus, which means that the special species associated with the spread of the Zika Virus are not needed for transmission to occur.  The Zika Virus and the worms that cause River Blindness are not the same. The comparison is made to show that some common species of flies – mosquitoes are flies – can spread exotic disease.
Black flies spend part of their life cycle as aquatic insects. For the most part, they are a pest of the Louisiana swamp areas, but in recent years, they seem to be spreading into Central Texas. What can you do at home to decrease these biting pests? Black flies are not the easiest pest to control. This is because unlike many flies, they hunt primarily by site rather than by smell. You can try wearing essential oils that are pungent, such as lemon and eucalyptus mixtures, DEET, and citronella. Those might reduce the risk of black fly bites, but they will not prevent them. The only effective way to deal with black flies is to trap them. Reach out to us for more options about black fly traps that do work.
-  Black Fly Outbreak in Central Texas – Texas A&M Agrilife Extension
-  Parasites – Onchocerciasis – River Blindness – Center for Disease Control
-  Onchocerciasis FAQs – Center for Disease Control
-  A Common U.S. Mosquito May Transmit Zika Virus Study Says – PBS.org