Thursday, April 9, 2015

Sticky Blue Balls

Sometimes we have company when we wake up in paradise.  Unwanted company.  Every dry season we are visited by the dreaded doctor flies, called such because their bites feel like the jab of a needle - a needle injecting a very painful substance.  Their sheer numbers and relentless drive for a blood meal have reduced this grown woman nearly to tears in years past.  One reason they are so abundant here is because their most preferred site to breed is mangrove swamp, a large one of which borders us to the west.  This website at the University of Florida has excellent information on Doctor Flies if you want to know more.  And as described on this resource page "Females are serious pests of mammals including humans, inflicting very painful bites."  Click here for a link to appropriate music to accompany this post. 

Dennis started an experiment a couple of years ago on methods to reduce their numbers.  He corresponded with Dr. James Cilek, a medical entomologist from Florida A&M University (more recently with the US Navy) to refine the "Sticky Blue Balls" method of entrapment.
Dennis hanging out one of his many sticky balls.
The idea for the sticky balls is that doctor flies are attracted to the color blue so they land on the balls and get stuck in the sticky.  These are just cheap blue beach balls that Dennis has coated with tacky trap glue.
"Come and get it!  Get stuck, that is!"
He hangs them up near the doors to our screened veranda and at key places outside.  And it works.  I was worried about collateral damage; it would break my heart to see a hummingbird stuck to one of the balls.  So far it has been only flying insects, predominately doctor flies.
Doctor flies love the blue balls.
Interestingly, only the female doctor flies bite and only the females are attracted to the blue balls.  The males eat pollen and nectar and generally stay in the swamp.
"Help me!  Help me!"
You can see more images of doctor flies, scientific name Diachlorus ferrugatus, at this site.
Balls at the front.
Dennis has hung them along the path through the mangrove swamp that goes to our boat landing in Black Creek, around the unscreened back veranda, and at other strategic places where people work around the property.  Most recently, to the approval of the crew, he hung them around the construction area.
Balls at the back veranda and near the banana plants.
Right now, Dennis has more than 30 sticky balls out.  Some are black, some are black and white, most are blue.  The doctor flies prefer the blue ones, but also go to the others.  Other insects prefer the black or white ones.  He periodically has to "debug" the balls and recoat them with stickiness.  He counts the doctor flies when does this to get an idea of how effective the balls are.  The numbers are mind-blowing:  last year with just a few balls he got 7413 over a period of about 3 months during the height of the season and so far this year the tally is at 16,793 from the first month of the season alone.  I could have been bled dry!

The true measure of their efficacy is that we are not bothered by doctor flies nearly as much around our property as we have been in the past.  The downside is that sticky balls get really nasty looking.   But not as nasty or painful as a doctor fly bite, so we will continue to use them.

Finally, I leave you with a link to perhaps the best skit ever from SNL -

Christmas Schweddy Balls Dec 7th 2003.  Go on - I know you were thinking about it.


  1. This just in - Dennis asked me to add the following:

    When Wilma and I first stayed at Steppingstones Retreat, 600 feet North up the beach, the owners commented upon the dreaded "Red Fly", which as it turns out is the dreaded Belizean Dr. Fly, and known in the USA simply as the Yellow Fly. The rationale for calling it a "Red Fly" was evident after what appears when you swatted one that had been feeding on your exposed tower leg, and also explains the Dr.Fly name as well for drawing so much blood. Wealso capture another biting black fly, so far unidentified, and a large number of horse flies.

    The reason the Yellow/Red/Dr. Fly is attracted to the glue balls has been suggested to be due to the polarization of light relected off the glossy surface. There is a published peer reviewed study on this aspect of attraction of biting flies to polarized light. But we humans also exhale attractant chemicals in our breath (carbon dioxide and a octenol derivative that smells like mushrooms, and which is also used to bait mosquito traps). Consequently we self-bait the traps near the cabana. The attraction of the flies to the balls may be complex, but the glue balls work. Thank you Dr. Cilek!

    Harrassment by biting flies is infrequent now. But we also use repellent lotions that might work, no study performed on this, but we feel it helps. When we are bitten, we use a spray containing menthol to mitigate the pain quickly.

    The biting fly abatement effort really has made being outside much more fun.


  2. The joys of living in Paradise Wilma.
    That is thoroughly unpleasant. I remember as a lad that gnats were bad enough (not that I ever encounter them now on my travels) they use to bite a lot, but this sounds awful.
    I didn't go much on the sketch though, I thought it was a load of ..... {:))

    1. We have more than the doctor flies, too. :-( I'll write about the sandflies at some point.
      Too bad you didn't think very highly of the skit, but I suppose Schweddy Balls aren't to everyone's taste. ;-)

  3. Never even heard of doctor fly before. My father used to put out half open jars of jam to trap wasps in the garden...........

    1. Lucky you to have been unaware of doctor flies! Dennis has another design to test out that traps them in jars, a variation of what your father did, instead on sticky balls. Whatever works!

  4. The Schweddy Balls skit was exactly my sense of humour. I had tears running down I was laughing so much.
    Pleased you have found a decorative way of lessening the Dr Fly problem. Don't think I would like to live near them. It's bad enough when my ankles get bitten by the occasional ant while gardening.

    1. Ant bites are plenty bad!
      Glad you enjoyed the skit. I don't know how they did it without cracking up.

  5. Thankfully, we don't have those flies here. I remember green fly season and black fly season in upstate New York and in New England -- and not fondly. And thanks for sharing that SNL link... Otherwise I would have been ashamed at what I thought when I read about Dennis's sticky blue balls!

    1. We had black flies in MN. It seemed the very air would turn black.
      Dennis asked me, in a sort of panicked voice, to please not title the post "Dennis's Sticky Blue Balls"! It brings to mind so many different interpretations ...

  6. Sounds like Belize's answer to the Scottish midge. We go to Scotland every year, and every year I get bitten to pieces. Carol doesn't, just me. They are so tiny they even get into my scalp, I end up with so many lumps that my head feels like a bag of ball bearings. You have my sympathy!!

    1. Black flies are very much like midges; they are beyond aggravating. Can't imagine having so many bites on my head. I bet Carol is glad that you are there to take the heat! Doctor flies are another thing altogether; larger with more painful bites. A single bite on a finger joint or elbow can be particularly swollen, red, and painful for several days.

  7. Wow, the true downside of living in paradise, what a nightmare those flies must be. Thankfully we mostly only have mosquitoes here in the southern UK and thankly, they rarely trouble me, must be my thick skin.

    1. They can be a real nightmare, Derek. And yes, our paradise is not perfect by any means. We love it anyway. Mosquitos, oddly enough, aren't generally too much of a problem here. That thick skin must come in handy for you!

  8. Hi Wilma,
    This is the most hopeful thing I've seen for possibly controlling Dr. Flies. Thankfully we don't have near as many as you do down there. I do have a question, where do you get the tacky trap glue? I've exhausted all our agriculture supply stores in Corozal. Getting the blue beach balls is no problem, just the glue.
    Great posting.

    1. Hi Dave - good to hear from you and so glad you like the post. Dennis orders the glue 4 gallons at a time! We use Easy Shipping to Belize based in Port Charlotte, FL. They are great; I highly recommend them.
      Here are the details from Dennis:
      Purchased from, 4X 1 gallon case. The cost was about US$200 and $30 UPS shipping. You can buy smaller quantities if you want, just search their online catalogue.
      The principal at is Eric Acosta.
      I paid via PayPal and had it sent to Easy Shipping Belize in Port Charlotte, Florida.

      Hope this helps. Cheers!

    2. The direct link to the TangleTrap product is
      Unfortunately, the manufacturer is experiencing a temporary shortage of one of the ingredients. Production of this formulation is rumored to begin again in a few weeks. Meanwhile, we have sticky traps, like the Deer Fly Patches,

    3. Hi Eric - thanks for adding the direct link to the tangletrap. It sure works great for us. Hopefully it will be available again soon. Dennis bought quite a bit! Cheers.

  9. I was wondering if the fly is attracted to the blue ball. Then wouldn't you want to place them as far away from the house as you can. By placing the ball close to the house are you not encouraging the fly to come into an area that you are trying to keep them out of? Thanks.

    1. Very interesting questions. Yes, you are correct that the blue color attracts the flies. Your suggestion to place the balls farther from the house is spot on - except for one thing - they are also attracted by the odor of humans (dogs, too) and that odor can be detected from farther away than the blue balls can be seen. So the flies would get close to the house anyway. To keep our bases covered, though, we do have some blue balls along the path to the marsh where they breed. As you point out, it is better to keep them away from the house as much as possible! Interestingly, we have noticed that if we don't have a ball about 10 ft. from the screen door, the flies ambush us as soon as we open the door. The little bastards!


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