10 reasons why you shouldn’t buy a bug zapper

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Although scientists have known for decades that bug zappers do not control mosquitoes, gullible Americans buy 1.75 million of them every year. To help get the word out I thought I’d create a more exhaustive listing of why they are a waste of money.

  1. They kill very, very few mosquitoes. By one count, 0.2% of the insects killed by a bug zapper were mosquitoes. I.e., they make essentially no difference in the number of mosquitoes in your yard. People who insist otherwise are delusional or lying. Companies that claim the devices kill mosquitoes can get sued.
  2. They can kill thousands of insects per day that are not mosquitoes. There’s no justification for this senseless slaughter even if you have somebody in your household who doesn’t “like” bugs. It’s also the case that zappers fail to fully kill many of the larger insects such as June beetles, so they are trapped inside dying, which nobody should be OK with. Plus an indirect consequence of removing tens of thousands of insects from your yard is that local birds will have less to feed to their young. And local bats will have less to eat. And you’ll have fewer pollinators flitting around your flower bed. Etc.
  3. Causes light pollution. That means you, and your neighbors, don’t get to see as many stars in the night sky.
  4. Causes noise pollution. That crackle (20-70 dB) might be hugely satisfying to those believing (falsely) that each sound is a from an exploding mosquito, but neighbors will probably be annoyed. Example 1 (reddit). Example 2 (Facebook). Example 3 (Houzz). Example 4 (Anchorage Daily News). Many homeowners associations (e.g., Estes Park, Fortville, IN) have bans against devices that make loud noises.
  5. Mist from exploding insects might contaminate your food when you are eating nearby. Research shows the debris from the explosion can travel up to 2 meters, and germs on the exterior of insects is thrown farther than that contained inside their guts (source). People who have yards filled with dog feces should take note of that finding. Same if you live close to where dead animals are common.
  6. Can deliver a painful shock if you stick your finger inside (e.g., like this report). Not usually a problem because of the presence of safety grilles but sometimes those fall off (e.g, Stinger Insect Zappers).
  7. Can catch fire and burn your house down. This is not a theoretical risk (Australia incident, Wisconsin incident). One model sold by Lowe’s caused 14 fires in the 1980s.
  8. Wastes electricity. It will cost something on the order of $15/year per this video (YouTube) just to keep the bulb going. But energy consumption spikes whenever the zapping takes place so the true cost is higher.
  9. They MIGHT confuse fireflies. Artificial light definitely interferes with firefly mating (article in New York Times), but I couldn’t find any research specifically using bug zapper bulbs (335 to 380-nm range). Several papers however suggest that near-ultraviolet light might be perceived by some species (Lall 1981, Carlson and Copeland 1985, Owens et al. 2018, Owens and Lewis 2022). The best support for my concern is from Moubarak and Niven 2026, who speculate that the translucent quality of the pronotal shield of fireflies has evolved to block UV light (presumably for reasons).
  10. They MIGHT attract yellow jackets. Again, I haven’t seen any research on this but my concern is based on the observation that yellow jackets forage for dead insects. E.g., all those insects on your car’s grille and windshield are often scavanged by yellow jackets. In general, you don’t want yellow jackets hanging out on your patio.
Shelf with boxes of bug zappers and other scam mosquito-control devices.

Should bug zappers be banned?

Current EPA rules suggest that citizens may submit reports of pesticide devices that cause environmental harm. Bug zappers remove so many insects they arguably are having a detrimental effect on birds and bats. Plus I’d guess that many are pollinators and the EPA (and states) have rules about pesticides and pesticidal devices that cause mass death of such insects. More information on how to contact state and federal offices can be found here. If enough people report the devices the agency might consider stricter regulation. It was estimated in 1996 that bug zappers killed over 71 billion insects each year in the United States. That number is probably doubled for 2026.

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Red wine trap for controlling Houdini flies at bee hotels

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Per posts on Reddit and Facebook, jars baited with malbec can trap Houdini flies (Cacoxenus indagator), an invasive kleptoparasite of solitary bees in the genus Osmia. The species was first reported in New York in 2011 and has since appeared in Maryland, Massachusetts, New Jersey, Oregon, Pennsylvania, Virginia, Washington, and British Columbia. For anyone with an insect hotel in an affected area, brood losses can be considerable so the news of a control method is welcome news. Currently hotel owners deal with the parasites by squishing them one by one, vacuuming them up, or trapping them on sticky cards situated in the eaves. All of these techniques seem futile given that a single Houdini fly can leave hundreds of eggs.

The trap

The general idea is to put the wine into a container that has small, fly-sized holes, then situate in a nook in your insect hotel. I opted to use 2-oz containers that I had sitting around but several posters on reddit use small mason jars. I then drilled four, 1/8″ holes in the lids, attached segments of cork with a 1 5/8″ screw to either the side of the container or the lid, and then screwed it to the hotel.

Evidence that it works

I set mine up too late in the season to estimate how many Houdini flies can be trapped per day, but I can confirm that some did go inside the traps and drown. Here are two:

Small waterlogged flies are difficult to identify even when you have decent photographs, so I eventually fitted the containers with sticky cards that would immobilize insects before they drowned. Here’s a trap attached via the lid and a Houdini fly that got stuck:

I should emphasize that my traps also caught dozens of small fruit flies that were not Houdini flies. So if you are trying this trap method be cautious in deciding whether it’s actually working or whether it’s just attracting small flies that happen to like red wine. I encourage everyone to use sticky cards and to submit photographs for ID confirmation to either BugGuide (North America only) or iNaturalist. If you opt for the latter you’ll likely get input from me within 24 hours (I’ve ID’d 200 Houdini flies already).

Is it safe for bees?

The holes are too small for many mason bee species but there are plenty of solitary bees that could fit into 1/8″ holes if they wanted to try. So far, however, none has become stuck in any of my nine traps. Some of the bees even use them as landing platforms because the sun hits them in the afternoon.

Design tips

Some thoughts that I’ll update as I continue with testing.

  • Opt for clear-sided containers so you have a better view of what is inside.
  • I’m now using a slightly smaller drill bit because 1/8″ allows rather big flies to enter.
  • Reddit user atrailofdisasters uses a red-pepper shaker, a solution that might work well for those who don’t have a drill and collection of small bits.

What wines work best?

Per reddit, the person who came up with the trap idea, Nicole Kenney, of Portland, Oregon, tested different wines for several years and decided that red wine, especially Argentinian malbec, is best. I have no idea how she did the tests but I’ll link to more information when I can find it. I’ve only tried malbec in mine but will do some comparisons next year during peak Houdini-fly season. Malbec is an old grape grown around the world but apparently thrives in Argentina and much of the acreage is in the mountains. It would be very interesting to know exactly which component is attracting the Houdini flies, of course.

Why does it work?

Houdini flies are members of the vinegar fly family (Drosophilidae) and are known to like fermenting fruit juice (source) so it’s not a surprise they are attracted to wine. And all animals are lazy so if there is food near where females are busy ovipositing, they will happily take a break to a have a drink.

More information

If you’d like to see photographs of Houdini flies I have about 20 on iNaturalist.

Please also see my blog post, “Houdini fly alert for owners of insect hotels.”

Annual cleaning of the insect hotels

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The cold and snow this winter have prevented me from taking many nature photographs, so it was a treat to have a look inside my two insect hotels. The one below is in the front yard. As you can see, it has a mix of hollow stems and wood blocks that have holes lined with paper straws. I split open the stems and unravel the straws to see who is inside, a process that is interesting but also allows me to kill any non-native, invasive parasites I find. I.e., I don’t want my hotels to be a breeding facility for pests and pathogens that might spread out and harm populations of local bees and wasps.

Bees

The most common mason bee this year was Osmia georgica, a native that can be recognized by its bright orange frass and circular, green, felt-like plugs that separate the cocoons inside the nesting tunnel. Here’s an adult if you’re curious what they look like.

There was also a mystery bee that is currently in a vial and will hopefully emerge sometime this spring. It’s unlike anything I’ve found before but somewhat resembles the cocoon of a resin bee. But much smaller than the cocoon of a sculptured resin bee (pic) that I often find in my hotels; this species is non-native and kind of a bully toward native species so they are unwelcome visitors.

Wasps

These are cocoons of Trypoxylon collinum, a spider-provisioning wasp (pic of adults) that I also get every year, especially in the front yard (maybe they like morning sun?).

I also got a few grass-carrying wasp pupae but I forgot to take any closeups (here’s one from past). For some reason the females prefer to nest in observational panel. The tunnels are full of grass and dead crickets but the larvae are there.

As always, some of the mason bee cells were filled with adult, dead Monodontomerus sp., a parasitoid. I can easily tell they are inside because they have partially chewed exit holes through the straw. When you unwrap the straw the adults are still inside the bee cocoon, apparently unable to exit because the straw is wedged into the drilled hole tightly. In the real world the wasps would chew through the stem and be able to escape. I have pics of larvae, trapped adults, and a female).

Flies

I’m not sure of the ID, but I found small dipterous (I think) pupae scattered around the observation window. Given their small size and the fact that grass-carrying wasps were the only residents, I’m wondering whether they might be scuttle flies, which are known to be parasites. E.g., Megaselia aletia (Medler 1965). I’ve saved the pupae and will attempt to get photographs of the adults.

Several of the mason bee cells were infested with the kleptoparasitic, non-native Houdini flies (Cacoxenus indagator, adult). I usually kill them but this batch is bound for a researcher who needs them.

Bugs

As in most years, the observation panel had several Dufouriellus ater individuals, members of the minute pirate bug family (Anthocoridae). I can confirm that they are minute but also that they rarely sit still and are thus a royal pain to photograph. The nymphs are bright red and even smaller.

Beetles

These two larvae are dermestids and were found inside mason bee nests where they had eaten several of the pupae. They are unwelcome residents and are an important reason why it’s important to clean insect hotels.

Spiders

There was a nest of spiderling jumping spiders in the observation window and they were unspeakably cute, with a thorax that looked liked hammered copper. Note that I typically relocate spiders when I find them on the hotel grounds during the season. For reasons.

Cleaning and restocking

In case of interest, all the pupae go into containers and placed in protected locations outside so that when they emerge in late March they can go on to live their lives. If I’m outside I’ll stop by the location multiple times per day to look for emergers to photograph.

I then bake the wood blocks to kill any remnant dermestid larvae, pollen mites, and pathogens that might be lurking inside. I also sweep out the house structure and drench it with a bleach solution. After everything is dry I’ll restock the house with blocks and stems.

Here’s an action shot of me making new stems sections with a cut-off blade attached to a Dremel.

If you’re envious, here’s where to buy an insect hotel. Or you can build your own. For help identifying a resident, please browse the “Bee and Wasp Hotels” project on iNaturalist. Send me a message if you have questions.