Traps for hornets: always scientifically justified?

Wandering in the countryside one can sometimes encounter some traps made of a plastic bottle filled with some liquid (usually beer or a sugar solution) in which hornets and other insects lie dead. Some of these traps may be part of a sort of network to verify the possible presence of invasive wasps. Anyway, it may be that most of the preys in such traps are native wasps.
I am not a zoologist, let alone an entomologist, so I wonder if such practice of spreading these traps in natural environments lie on a real scientific basis or is something more like a commonplace.
I also wonder if this practice can have more benefits than disadvantages or if it can cause impacts on native insects and, in the case, if there are studies on these possible impacts.

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Many traps associated with a scientific protocol will likely have a small tag or explainer with contact info on them or perhaps research permit info.

In most cases, it’s unlikely that a few traps are going to have a large population level impact, so I wouldn’t bother the traps. If there is a tag, you could contact the person to ask about the study.

If you’re concerned about them and there is no info, the first place I would check would be with whoever owns/administrates the land. If it’s private land, the landowner might want to know if someone is trapping on their land without permission. If public, the admin/rangers/whoever should know about all scientific studies or control measures occurring with permission. If the activity it unpermitted, they’ll want to know as well.

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Studies where they catch lots of different insects hopefully also save everything that they catch (you can keep stuff like this pickled in alcohol or formalin) so that even if they are only interested in say screening for one invasive species, other researchers could use the samples later to survey overall diversity, or students practicing insect ID could use them, etc.

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no word about whether “the countryside” is referring to wild spaces, or people’s living spaces, or what. but such traps are fairly common in the US where people want to keep yellowjackets away from their picnics, yard spaces, etc. people with severe allergies to bees/wasps are going to be more likely to be pretty diligent about this.

I’d like to learn more about what actual policy if any is on this, but have assumed there may be none to protect wasps or that it’s permitted as “pest control” by a human safety justification, for example in parks to prevent stings, allergies, etc. Wasps also have some conservation and pollinator value along with bees and other pollinators, although social vespids can also be among the aggressive insects.

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I’m not allergic but we put out traps specifically for yellowjackets (Vespula pensylvanica) to keep them from nesting in our garden. We check them daily and release any other insects that get caught, even paper wasps, but that rarely happens. I’m sure others are not as selective though. Most of the stinging insects don’t bother us at all but the yellowjackets are aggressive and very territorial and I got tired of being stung while gardening. They’re certainly not at risk of local extirpation because we trap thousands every year and have seen no decline in the local population due to our traps.

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If you don’t mind me asking, why do you trap wasps in your garden if you’re not allergic? They are very helpful in pollination and killing of caterpillars and other critters that would like to eat your plants.

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so you like being attacked by wasps when you’re just coming and going from your house?

just because someone isn’t allergic doesn’t mean that stings aren’t painful.

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We only trap the specific wasps that are aggressive. Even though I’m not allergic, the stings are very painful and cause a large swelling that itches for several days. They would even get into our house and sting us. We still have lots of paper wasps and mud daubers which are very docile. There are also yellowjacket workers in the yard and they don’t sting when they’re just foraging. But we won’t tolerate the nests in the garden anymore because we actually like to use our garden to grow food.

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