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Flies in a home are a complicated issue

June 28, 2019
Close-up of fly

Dear Dr. Tim,

I have a simple question. Can you tell me how to get those pesky flies out of my home? You know the ones I am talking about – those obnoxious black ones, the ones that really annoy you.
Thanks for your help.
Ann Oyd (aka annoyed)

People seldom appreciate what it takes to become a professional entomologist – let alone one trained as an insect diagnostician. First is a natural aptitude for science, then 4 years of undergraduate studies, then 2 more for a master’s degree, followed by another 4-5 for a Ph.D. (4 is minimum for the really smart ones – let’s just say 6 in my case) and for some several years on top of that as a post-doctoral student. So, becoming a professional entomologist is not as easy as one might think. I say this because with that much training and experience, it is absolutely impossible for me to give a simple answer – even for a simple question.

Some time ago an older gentleman and his daughter came into my office, referred by an Extension person in a nearby county. It was clear from his impatient demeanor that he was feeling like they were getting the proverbial runaround. His more patient daughter began with an introduction. She explained that he was recently widowed and that, while she was trying to take over some of the cleaning and housekeeping for him, she noticed flies in the house and came seeking professional advice as to what to do and what – as her father insisted – they could spray that would get rid of them.

I could not help but notice her father, in bib overalls, leaning against the back wall, arms folded, biting his tongue, clearly having contractually agreed to let his daughter do the talking.

“We have flies in my father’s house and would like to know what you recommend for control.”

“What kind of flies are they?”

“Well, I don’t know – black with wings. We thought you would know.”

Due to my aforementioned professional training and many years of experience, I know that a description “black with wings” is not enough for a proper fly identification. There can be many kinds of flies inside a building, and each is different. First there is the common house fly. It can certainly be described as black with wings, but so can its close cousin, the flesh fly – although the flesh fly has characteristic white stripes on its thorax and spots on its abdomen. Blow flies are also similar to house flies. Most, but not all, have a subtle iridescent coloration on the thorax and abdomen. Attic flies definitely are black with wings as well, but have golden hairs on their thorax – although you would need a microscope to see them.

Specific identification is important is because it dictates control recommendations. For example, each fly has its own biology and behavior. House flies feed and lay eggs in and around trash cans and dumpsters and can largely be kept out of a home with sanitation and window screening. The odd one that gets through can be taken down with a household labeled aerosol spray or with a fly swatter. Attic flies, on the other hand, look just like house flies but do not feed on garbage. They enter a home to avoid harsh weather outside. Flesh flies and blow flies also may look similar but are stronger fliers. They develop on carrion or dung, sometimes breeding long distances from the home.

Control recommendations are different for house flies than for attic, flesh or blow flies. Add to these any of several other smaller fly possibilities, also black in color, also found in homes. Fruit flies, phorid flies, and moth or drain flies are all commonly found indoors. Most often each occurs in a different part of the house, feeds on a different food source and therefore must be controlled in a very different manner.

Considering all of this, you can see how the description “black fly in house” may not provide enough information to allow a professional entomologist to render an accurate identification or control recommendation.

Trying to glean more information, I ask, “And where are you finding them?”

“The flies are in the kitchen, mostly – well, actually through the whole house, right, Daddy? Where do you see it mostly?”

She turns nervously to her father, who is clearly becoming impatient. He sighs audibly, apparently realizing that this may take considerably more time that he had hoped. “I see it in the house. THE FLY IS IN THE HOUSE.”

“Does it occur in a particular part of the house?” I probe, hoping for more detail.

“It flies around. It has wings, you know, so it is all over the house.  What kind of question is that … what part of the house?”  he mumbles.

“So, this fly of yours, what does it do?” I ask this knowing that the fly’s behavior can sometimes give a clue to its identity.

Daughter:  “Well, it buzzes and flies around and makes a nuisance of itself. Dad, what do you see it doing in the house?”

He sighs again and starts talking very slowly, articulating every word. “IT FLIES.  IT FLIES AROUND THE HOUSE. That’s what it does. It flies”

I’m trying to diffuse the tension. “So you have to understand, I am trying to help figure out exactly what the fly is so that I can help you solve your problem.”

He elbows his daughter out of the way and approaches my desk. “Young man, we know what it is. It is a fly.  We came here to find out what spray to use on it.”

I sense that he is struggling to control an urge to grab me by the ear. “It is a bloody fly and it flies around. That is what flies do and it is why they are called flies. Now tell us the name of the spray – we need a spray.”

He jabs a boney finger on my desk, glares and repeats his demand in an ominously threatening, almost whispery voice – just like in the “Godfather” movie. ‘‘Give … me …  the …. name … of … the …. spray.”

“But, sir, there are several different possibilities – we have to first get the specific identification correct before we can make a recommendation. There are subtle differences in flies. For example, if it has golden hairs on its thorax, or if it has a striped –”

The father cuts me off. “The spray, son. Just give me that the name of the spray.”

“Well, it is not quite that simple. You see, there are many possible control techniques and depending upon what it feeds on and where you mostly see it.  Do you know where –”

He Interrupts again. “You think I don’t know?  IT IS IN MY HOUSE – THAT’S WHY I am here. If it was outside it would not be bothering me and we would not be here!”

Holding his head with both hands in disbelief, he says. “NOW I WANT IT KILLED.”

I don’t dare ask if he sees it in the daytime or mostly at night, if he lives on a farm or in the city, if he keeps windows open or has proper screens, whether it is a recent occurrence or if he has been seeing it for some time. Those are all important need-to-know questions, but he’s now red-faced and visibly shaking.

His daughter mercifully ushers him away from my desk.

“Since you don’t have a specimen with you I cannot say for certain what it is.  And, until I know what it is, I cannot confidently tell you how to control it. Fortunately, we have a laboratory set up where you can send a sample. It is called the Plant and Pest Diagnostic Laboratory – PPDL for short. Simply catch one, put it in a leakproof vial of rubbing alcohol, fill out the required form, which is online, and then mail it off to the PPDL. We will identify if for you and then provide control recommendations.”

From the back of the room the father looks heavenward and spreads his arms wide. “But I don’t want control recommendations. I don’t catch flies and put them in bottles. I don’t want to chase it all over. I want to kill it!”

His daughter intervenes again, like a trained mediator. “Now Daddy, he is just trying to help. Dr. Tim knows all about these things. If he needs to see the fly we can get it for him – can’t we, Daddy?”

A week later I received a specimen in the mail. I recognized the name of the submitter immediately. It WAS preserved in a leak-proof container. The box DID contain the proper form. It was filled out exactly right, and I could tell from the handwriting it was done by the daughter. However, taped to the bottle was a note, written in a shakier hand.

Here is the FLY.
It is now dead.
Obviously, we don’t need your help any longer.

Inside the vial was the specimen. It was pretty beaten up. I could only imagine the old man chasing it. The fact that its guts were squished out, legs bent in unnatural ways, and one wing was missing suggested that it was whacked with a rolled-up newspaper.

Though smashed, it was recognizable: A common house fly.

My final report indicated this and my recommendation: A quick burst or two from an aerosol can of Raid® should kill it. Then I signed with my usual, Dr. Tim, Ph.D., Insect Diagnostician.

His thank you note must have gotten lost in the mail.

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