Saturday, July 27, 2013

Our Deer Fly Population Is Significantly Lower This Season

Well, folks, this is my first post with actual trapping data from the 2013 deer fly season.  I have had to wait until now to post my data because I didn't have enough data to report until now.  This is due to the fact that the number of deer flies on our property this year is significantly lower than that of any previous deer fly seasons we've ever experienced (this is our 23rd season).  I saw our first deer fly of the 2013 season on June 16,  but it was a full three weeks after that until I saw a significant number of them here.  And even then they didn't seem very bad at all.  Throughout the entire season thus far, I have not observed a swarm of deer flies around our cars when we drive down our driveway.  Usually there is a thick dark swarm of them buzzing around the moving cars, to the point where we have to pause and wait a full minute or more before opening the garage door in order to give them time to dissipate before we drive into the garage.  But that's not the case this year.  This year we barely see any flies at all swarming our cars!  Additionally, I have not even had to wear a hat while I'm playing or working outdoors so far this season.

I hate to jump to conclusions, but I think trapping nearly 13,000 deer flies last season has made a big impact on reducing the deer fly population on our property this season.  I'm not sure what else to attribute this great reduction in deer fly numbers to.  We've had plenty of rain this season.  Nothing has changed on our property or in the surrounding areas.  I'm walking the same areas for the same amount of time for each trapping session as I did last season.  There is just nothing else that I can think of which could be responsible for these low deer fly numbers this year.  In fact, we continue to see very few dragon flies this year, which I would have thought would have resulted in higher deer fly numbers.

So, again, while wanting to not jump to any conclusions before all the data is in and before other explanations are considered, as of now I can't help but restate my opinion that my trapping of nearly 13,000 deer flies last season has made a big impact on reducing the deer fly population on our property this season!!

Here's a look at my 2013 trapping data thus far.  Notice that this season I did not start trapping deer flies until the 23rd day of the season ... the season started on June 16 with my first sighting, and I didn't conduct my first trapping session until July 8 because there just didn't seem to be enough deer flies to justify going out to trap them.  (I am slightly regretting not having gone out to start trapping earlier in the season because now I've allowed those few deer flies time to breed.  Oh well, next year I'll start trapping even when there are only a very few deer flies around.)  Due to my schedule and to morning rains, I was not able to go out trapping every day after I first started, but then I became consistent.

OK, here are the numbers for this season so far:

Now let's compare that to last season's data.  This first chart compares the data from 2012 (in red) to the data collected thus far during 2013 (in blue).  These data have been aligned by date.

However, the 2012 deer fly season started 15 days earlier (first sighting was June 1, 2012) than the 2013 season (first sighting was June 16, 2013).  [Remember, 2012 was the year where spring came very early and was very warm.]  Therefore, another way (and probably the correct way) to compare the data from these two seasons is to align them based on the point of the season (not the actual dates).

Here, then, is a comparison of last year's data to the data collected thus far this year, this time aligned with respect to the point of the season (i.e., days into the season, with day 1 being defined as the day of my first sighting for each season).

Rather interesting, don't you think?  Seems that trapping does indeed cause a significant reduction of the next year's population of deer flies!

So how is your deer fly season going?  Are the number of deer flies you are seeing this year significantly different than what you've experienced other years, or is this season fairly typical for you?  I am very interested in what other observers (and, especially, trappers) in Livingston County, Michigan, and neighboring areas have noticed this year with respect to deer fly numbers.

I will post again when I have data collected for the remainder of the 2013 deer fly season.  In the meantime, happy trapping!

Got questions?  Got comments?  Got feedback?  Click the blue "# comments" below and say something!


  1. Wow, that's a drastic reduction. I would certainly hope and love for the answer to be, in fact, that your previous trapping is the sole cause for the reduction in fly count.

    However... I am also seeing a significantly lower quantity of flies down here in Washtenaw county, and I surely did not trap enough last year to affect my local population. (I wear a trap hat as a form of bite mitigation, not population control). Last year I could trap 50+ on my hat in a couple hours of field work. This year, I've only gotten 6-10 per session. The hat is still critical though, mind you! Even just a couple bites are painful and cause big welts, so the trapping method is still a beautiful thing.

    I can't imagine why we would have so many less flies this year though, the weather seems perfectly suitable. Is this just a more "normal" year, where last year was especially bad? The sustained dry heat of last year could have led to extra hatching? I dunno.

    1. I dunno either. One thing about this season that I keep being surprised about is the fact that we haven't been experiencing swarms of deer flies around our cars when we drive down our driveway (which is 1100 feet through heavy woods). This has never happened, never never never, in the 23 years we've lived here! Maybe last year's early start of the deer fly season and the extremely dry conditions had an effect on this year's crop. Maybe that messed up the incubation and maturation of last year's eggs and larva? Again, I dunno! But I sure am enjoying the extremely mild deer fly season we are having this year, regardless of the reason for it!!

    2. Umbrella Girl:

      Have you experimented with deer fly prevention such as sprays or bug repellants?

      I walk 3-dogs in the woods of Livingston County on a daily basis. I have been bitten so bad on some days that you could read the bumps on my face like a page of braille. My dogs suffer as badly as I do sometimes. I had to take one of my dogs to the Vet for a prescription of antibiotics and antihistamines because of all the lumps on her from deer flies.

      I started wearing a ball cap with a bandana tucked in on the back side to protect my neck. I spray the hat and bandana with horse fly spray and use a 40% DEET mosquito spray on any exposed skin. This has helped, but if you leave a 1" square of skin unprotected then they'll bite you there.

      I spray my dogs with the same fly spray and use a clean linen rag to apply it carefully between their eyes and on their ears(favorite spots for deer flies).

      This all helps but is not a cure for the problem.

      One interesting thing I have seen with the deer flies is their choice of dogs. Annie a 5-year old black lab is plagued by the flies. She is a magnet for flies and mosquitoes for some reason. Elliot a 5-year old Terrier does not seemed to be bothered much by the flies weather he is sprayed or not. I not sure why my lab attracts so many flies compared to the Terrier. They are both black so color is not an issue. I am not sure what is the attraction for the Lab.

      Have you developed any defense from the flies?

    3. Oh my, sounds like you and your dogs have to go through quite a routine just to go on a walk in the woods. Boy oh boy, those stupid blood-sucking deer flies sure are universally annoying!! I have never experimented with sprays or lotions or whatever as deterrents or repellants, neither for humans or for dogs. I had read in several places that such things don't work with deer flies. The reasoning behind this is that deer flies are not filth flies,such as house flies are, and, therefore, are not attracted nor repelled by odors. They do not, for example, swarm around poop. Instead, they are attracted by motion. However, one certainly cannot argue with your experience of being able to lessen their attack with sprays. I am glad to hear that works for you and your dogs!

      I, unfortunately, do not have any great knowledge or experience to share with you regarding better sprays, as I have never tried any.

      Amazingly, I have never been bitten by a deer fly. Not once! I consider myself extremely lucky!!!

      hoping your trails are soon free of deer flies!


    4. There is a deer fly patch made by a company called Detex out of Leroy, MI. I bought hundreds and use them when I run and mow my lawn and food plots and they work. You apply it to the back of a junkie hat (as it will eventually ruin it) and they will attack the patch and not you. As for the dogs, I also have a black lab and husky and they attack Black, unless I walk in front or very near (as they seem to attack the higher object). I would do what umbrella girl does and you will not ever get bit, and I do not think your dogs will either. Plus you will be removing thousands of females and their eggs.

  2. I am the guy that posted a comment a little over a month ago about this being my 2nd season of trapping in Livingston county. Although I use a different method (2 coated cups attached to the front of my enclosed atv), I trapped over 7000 last year and under 2000 this year. By removing over 7000 females, (the only ones that bite and attack) I removed over 7 million eggs (each female lays approximately 1000 a season). I went out 2 times each and everyday (rain or shine) last year from June 1 to August and this year as well. I have to believe it is working. We will see if next year is even less. Keep us posted if you are still going out. I surely will until I do not catch a single fly in the morning or evening. I do not want a single breeder to escape. I know it is impossible to completely eradicate, unless everyone trapped, however I like what I am seeing and will continue to trap until I see no more!

  3. Great to hear from you again, Fly Trapper! I was wondering how your deer flies were this year. So happy to hear you're experiencing a greatly reduced population. I am very impressed with your consistent efforts and dedication. As I stated previously, I'm a bit upset at myself for not starting my trapping earlier in the season this year and, thus, having allowed the first batch of flies (although low in number) to breed. I am, however, planning to do exactly as you and to continue trapping each morning this season until I trap zero deer flies. And next year I will start trapping immediately after spotting the first one of the season.

    Wouldn't it be awesome if one summer we could get a countywide effort together to trap deer flies? Imagine the impact that might have. Seems like the Michigan DNR should like something like this. Afterall, if deer flies could be eliminated or at least greatly reduced, that would allow people to enjoy the state parks and game areas all summer long.

    1. I noticed that I catch 3 times as many in the evening. They must know the deer are coming out of their beds to feed. I also tried the bag over the cup vs just the cup painted and the shiny blue cup caught over three times as the bagged one. You caught almost double what I did last year, so I am not trying to tell you how to do it, but give it a try and see what happens. The other benefit is no need for gloves as I leave the bottom inch or so to hold the cup and then I just stack the cups inside the garbage bag inside of each other covered in flies. I use 2- 50ct bags of cups a year at $2.50 a bag from Kroger. I also use the paste and a wood spatula vs the one with the brush. The paste is half the price and double the consistency, according to Contech, the new supplier of Tanglefoot.

      I love the idea of trying to get the DNR involved, or even better, every neighbor of ours!

  4. Thanks for reporting your observations, Fly Trapper. I will have to try the baggie vs. no baggie test. It is also interesting about the evening vs. the morning. Does make sense. I'll give that a go, too. Might not get good data about that until next year, as this year's crop of deer flies is already waning (yippeeeeeeee!!!)

  5. Hi all. We too are trapping for about the last 4 years and feel the numbers are down. We live in howell twp and of course in Livingston county. Bob and Pam.

    1. Hello, Bob and Pam, I have the same question as Fly Trapper. Namely, have you seen a decline in deer flies since the time you've been trapping, or is it just this season that you're seeing the decline? Do you feel (or have data to support) that your trapping has any effect on the subsequent year's population, or does it merely have an effect on your enjoyment of the outdoors for the year during which you are trapping? And when I say "merely", I certainly don't mean that having an effect for the current year is a small thing. Quite the contrary, even if it is proven that trapping has absolutely no effect on the subsequent year's population, I would still trap deer flies!

      Nice to see that yet another household in Livingston County is engaged in deer fly trapping!! What method or contraption are you using? What kind of numbers are you trapping?

      BTW, I am in Deerfield Twp, at the northern edge.

    2. UmbrellaGirl:

      Interesting website! Your fly trapping is a real service to mankind. Deer flies make it hard to enjoy our woods and forests in Livingston County.

      I walk my dogs in the Brighton Recreation Area on a daily basis. I have not seen a reduction of deer flies this year compared to last year. They are pesky and persistent as ever in 2013.

      Your 2012 fly trapping may have done more than you realize for your area. Where I walk, there is no fly control and the flies are as bad as ever. As of this morning August 11, I have not noticed any reduction in numbers of deer flies. So your fly season is ending now while mine in an untreated are is still going strong.

      Good luck with your project

      Julian Meade

    3. Thank you, Julian, for your report from Brighton. Good to know, but bad for you and your dogs! Maybe some folks in Brighton need to become umbrella girls and guys ... and dogs!

      I hope your deer fly season ends soon!


  6. Hi Bob and Pam,
    Do you feel they are down from your trapping efforts? Have you noticed any decline from removing egg layers from the population. I am only on my 2nd year so I do not have the data you have with 4 yrs. I am still trapping! Thanks

  7. Well, any numbers updates for us, UmbrellaGirl?

    We are nearly fly-free down here in eastern Washtenaw county! It's a beautiful thing.

    1. Hello Ross. I will be posting my final numbers for this season sometime next week, as I am traveling this week. So stay tuned!!

  8. Still trapping! Caught about 20 yesterday. When will it end?


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