Does a Bag of Pennies Keep Flies Away??

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Key Takeaways:

  • Hanging a bag of pennies in water is a popular DIY method some claim keeps flies away.
  • While no scientific evidence proves this method’s effectiveness, many anecdotal reports suggest it works.
  • Theories on why this method may deter flies include magnification, reflection, and visual distraction.
  • As a low-cost, non-toxic option, it may be worth trying for those dealing with flies.
  • Its effectiveness likely depends on specific circumstances and fly behaviors in each area.

Introduction: Why Do People Hang Bags of Pennies to Repel Flies??

Does a Bag of Pennies Keep Flies Away??

With the onset of summer comes an annoyance familiar to many – pesky flies invading homes. While flies are usually just a nuisance, they can also spread bacteria and diseases. This leaves many searching for safe and effective ways to keep flies at bay. One popular do-it-yourself method involves hanging plastic bags filled with pennies and water. But does a bag of wet pennies actually keep flies away?

This notion has circulated for years with many claiming it works wonders. However, there is no scientific research available that confirms or denies the effectiveness of this penny bag method. With no concrete evidence, some remain skeptical that just water and pennies can serve as an effective fly deterrent. Despite the lack of studies, proponents stand by the method and suggest several theories on why it seems to keep flies away for them.

This comprehensive article will explore the popular penny bag claim. It will cover the anecdotal evidence behind it, analyze the possible scientific explanations for its supposed effectiveness, look at factors impacting results, and provide tips for trying this inexpensive, non-toxic DIY fly deterrent. With pesticides and traps having potential downsides, a bag of pennies may offer a simple way to curb pesky flies without chemicals or mess.

How Do You Make and Use a Fly Repellent Bag of Pennies??

The process of making a bag of pennies fly deterrent is quick, easy, and inexpensive. Here are the simple steps:

  • Take a sealable plastic bag, like a zipper storage bag. Quart size or similar works well.
  • Add approx. 1-2 cups of copper pennies to the bag.
  • Fill bag with water until almost full, allowing some air space.
  • Seal the bag tightly to prevent leaks.
  • Hang or tape the water-filled bag in desired fly problem areas.
  • Reuse for months by simply adding more water as needed when levels decrease.

The pennies and water can be reused continually. So the only real expense is an initial supply of pennies and a reusable plastic bag. People hang the bags by doors, windows, food prep areas, garbage cans, patios, or other spots flies tend to congregate. The bags can be mounted with string, tape, or hooks. Some suggest moving them around periodically or using multiples bags to cover more territory.

What Evidence Exists That Pennies and Water Can Repel Flies??

There are currently no scientific studies investigating the effectiveness of hanging water-filled bags of pennies to deter flies. However, there is abundant anecdotal evidence found online and shared through word-of-mouth.

Many people report noticeable reductions in annoying fly presence after trying this inexpensive trick. While anecdotal, the volume of shared experiences lends some credence to the claims that bags of wet pennies may actually help combat flies.

Some of the user reports and reviews on this method include:

  • A science teacher shared they hang bags of pennies around their classroom at school and feel it makes a huge difference in fly control.
  • A farm owner noted fewer flies in their barn after starting to use the pennies technique and hasn’t used insecticides since.
  • An avid gardener mentioned flies stopped swarming their compost area after adding some penny bags nearby it.
  • Reviews shared by shoppers on retailers’ websites often mention success with pennies for deterring flies around patios and picnic areas.

While controlled studies are still needed, the abundance of positive anecdotal evidence suggests this traditional trick may have some scientific merit. At the least, it indicates the method is worth a low-cost try for those struggling with bothersome flies.

What Are Some Theories on Why Pennies in Water May Repel Flies??

With no direct research available, experts can only hypothesize on why hanging bags filled with pennies and water may help control flies. Some of the leading theories include:


Some suspect the water may magnify and enlarge the image of the multiple pennies stacked at its bottom. This enlarged repetitive coin pattern could mimic the appearance of a larger threatening insect or the multifaceted eyes of predatory bugs. If so, it could potentially scare or confuse small flies away.


Others think the key factor is the reflective quality of the water and copper pennies. As sunlight hits the hanging bag, it creates flashing reflections that move and bounce around the room. Some experts propose this constant reflective motion may overstimulate flies’ sensitive compound eyes. This could make them avoid the immediate area.

Visual Distraction

Another view is that the bag’s shimmering pennies simply provide an ever-changing visual field that is distracting or disorienting for flies. Their compound eyes may struggle to process the complex bag image buzzing with reflections and movement. Rather than closely investigating it, they steer clear of the overwhelming visual stimulation.

While still unproven hypotheses, these possible mechanisms provide plausible explanations for how bags of wet pennies may help repel nuisance flies via sight-based effects. Ongoing research is still needed to confirm if any hold true.

What Variables May Impact the Effectiveness of Pennies Against Flies??

Assuming the pennies in water method does help deter flies via mechanisms like magnification or reflection, there are likely variables that impact its success and usefulness in different settings. Possible factors include:

Fly Type and Behaviors – The specific fly species present and their behavioral patterns could influence results. For instance, bottle flies are drawn to light which may make them more affected by flashes of reflection. But fruit flies follow scent and may be less distracted visually.

Bag Placement – Where and how the bags are hung in a space can matter. Positioning near prime fly activity spots may work better than random areas. Outdoors, bags likely need sunlight exposure for maximum reflection.

Number of Bags – Using multiple bags to create a “minefield” of visual barriers may improve fly control versus relying on just one.

Bag Size – Larger bags allow more coins that can generate increased reflection and motion effects compared to tiny bags.

Penny Oxidation – Brand new shiny pennies likely create more flashing reflection. As coins oxidize with age, their reflective quality may decrease.

The ideal setup of bags for targeting flies may require tweaking locations, size, quantity, and penny shine factor to enhance results based on environmental factors influencing fly behaviors and vision.

What Are Some Tips for Using Pennies in Bags to Deter Flies Effectively??

If interested in testing out this traditional trick, here are some tips that may help boost success:

  • Choose sealable, leakproof plastic bags – durable zipcode bags or snack bags work well. Avoid bags prone to tearing.
  • Fill bags nearly to the top leaving just a small air space to allow water movement.
  • Use bright copper pennies for maximum reflectivity. Mixing in some zinc pennies can also add contrast.
  • Position bags on south-facing walls or windows to capture ample sunlight. Reflection intensity depends on light exposure.
  • Experiment with hanging bags in different spots to target key fly entryways and congregation areas in each setting.
  • Trying using multiple smaller bags distributed around rather than relying on one bag alone.
  • Maintain shine by wiping down existing pennies or adding new ones when oxidation reduces reflections.
  • Pair with other deterrents like essential oils, vinegar traps, or sticky tape for added effect.

With some strategic planning, penny bags may be able to work visual magic on flies and enhance pest control efforts. Monitor effectiveness and make adjustments to maximize results.

Can Hanging Pennies Deter Other Pests Like Wasps, Bees, Mosquitoes, or Spiders??

Does a Bag of Pennies Keep Flies Away??

The penny bag method appears primarily aimed at controlling flies. But could it also help deter other insects like wasps, bees, mosquitoes, or even spiders? The limited evidence available indicates mixed results with other pests:

Wasps and Bees – Anecdotal reports suggest bags of wet pennies may also help repel some wasps and bees. As flying stinging insects, they may also be impacted by the proposed visual effects. However, more scent-driven bees seem less affected.

Mosquitoes – There is little evidence indicating this method deters mosquitoes. As they are drawn to targets by chemical cues and carbon dioxide, visual effects seem less relevant to mosquito biology. Other strategies like eliminating breeding grounds are likely more effective for them.

Spiders – Spiders may not be impacted at all. Most spiders have poor vision and rely more on vibrations. One bag of pennies would likely do little to deter or visually distract spiders within a building.

While pennies may primarily impact flies, further investigation is needed on effects against other insects. The visual mechanisms theorized to drive fly deterrence may produce limited results for insects drawn by other cues like smell.

Are There Any Risks Associated with Hanging Bags of Pennies for Pest Control??

Overall, hanging bags of water and pennies to control flies comes with minimal risks assuming proper precautions are followed:

  • Choking hazard – The coins pose a potential choking risk for kids and pets if bags break and pennies spill. Hang out of reach and inspect for damage.
  • Slips and falls – Leaking bags that drip water onto floors could create slip hazards. Catch drips promptly and store bags away from high traffic zones.
  • Legionnaires’ disease – Stagnant water could theoretically harbor Legionella bacteria if left for very extended periods. Avoid by changing water as needed.
  • Metal leaching – Over time, copper from oxidizing pennies may leach into the water. Avoid contact or consumption of the water.

With careful bag selection and placement, renewal of water, and keeping out of reach of children or pets, risks remain very low for this inexpensive fly fix. Caution is advised, but overall penny bags present a far safer option than chemical sprays if used responsibly. Monitoring conditions and exercising common sense can allow their safe use.

Are Pennies and Water an Effective DIY Fly Control Strategy??

While scientific proof is still lacking, the volumes of anecdotal evidence suggest bags filled with pennies and water may be an effective, wallet-friendly way to control pesky flies. Hanging them in key areas provides a non-toxic technique safe for children and pets. Before resorting to risky chemical treatments, give the penny bags a try. With very little to lose and no harsh chemicals, the brilliantly simple bags provide an ideal first line of defense in tackling fly issues. Just be sure to take basic safety precautions like stability and slip risks. Evaluate results in your own environment and make adjustments to placements and setups as needed to maximize fly deterrence. With a glimmering arsenal of pennies and clever placement, you may be surprised just how powerful this traditional trick can be in driving flies away from your space.

Frequently Asked Questions About Using Pennies in Water to Control Flies:

Why do flies avoid areas with bags of pennies hanging in water??

While not scientifically proven, the main theories are that the magnified reflections and ripply flashes of light overwhelm and confuse flies’ sensitive compound eyes, making them avoid those areas. The repetitive, moving reflections may also mimic larger threatening insects that flies instinctively steer clear of.

How many pennies should be put in each bag of water?

A good rule of thumb is 1-2 cups of pennies per average quart-sized sealable bag. The amount needed can vary based on bag size, but aim for 100-200 pennies to create plenty of reflective effects. Just be sure to leave a small air space at the top when sealing the filled bag.

How often does the water need to be changed in penny bags?

Change the water every 2-4 weeks to prevent stagnation and maintain the rippling effects. Check bags occasionally for any leaks or drips. Catching drips promptly can allow the same pennies and bags to be reused continually.

Should the bags be hung in direct sunlight for best results?

Yes, direct sunlight hitting the bags maximizes the reflective effects. Hang them in south-facing windows or on walls/eaves that get ample sun exposure throughout the day. Avoid shady areas blocked from sunlight.

Can anything be added to the water to enhance the fly repellent effects?

Avoid adding anything to the water, as impurities may reduce the light reflectivity. Plain water allows maximum shine and ripple effects. If bags require cleaning, use water and mild dish soap then rinse well. Let fully dry before reusing.

How long does a bag typically last before needing replacement?

With proper care, the same plastic bags can be reused for many months. Look for quality bags resistant to leaks. Check periodically for damage. Replace bags showing any splits, holes, or weak seams to prevent leaks before they occur.

Should bags be paired with other natural fly deterrents for maximum effectiveness?

Yes, combining bags with additional natural fly deterrents can boost overall results. Good complementary options include essential oils, vinegar traps, or sticky tape. Used along with penny bags, these can enhance control by utilizing multiple repellent strategies.

Are penny water bags helpful for controlling flying insects other than just house flies?

Current evidence indicates the visual effects may deter some other insects like wasps or cluster flies but has minimal impact on mosquitoes or spiders. The method seems most effective against fly species strongly guided by visual cues and compound eye sight. More research is still needed on effects on other pests.

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