Why do entomologists kill bugs?

The paradox

I like bugs. I also kill bugs. Now I don't enjoy killing bugs, but it is a crucial part of entomology. The average person often seems to fall into one of two camps - those who respond to pictures of spiders with "burn it with fire," and those who take offense at the thought of squishing a bug. This article is geared more towards the latter group to help explain why killing bugs is necessary to advance the field of entomology. Although if you are of the opinion that bugs should be killed indiscriminantly, my hope is to instill in you a curiosity about bugs.

Why do we need insect collections?

Entomological collections are a goldmine of information. When a new species is described, the specimen used to describe the species (aka the holotype) is deposited into a collection (hopefully with other specimens - the paratypes). If there is any question about that classification - such as whether two species are actually the same species or if a species needs to be split into multiple species - that original specimen is available to be re-examined. With over one million described species of insect, ¹ those specimens are invaluable resources.

Identifying insects can be hard. Some insects are easy to identify (such as monarch butterlies), but others require microscopic dissections of their genitalia. That is not something you can do out in the field or with a photograph - an actual, physical specimen is required.

Entomological collections also serve as historical records. With each specimen in a collection are the date and location that particular specimen was collected. Now the usefulness of this data is limited by how extensive the collection is, but it can help track the spread or decline of insects across geographies and over time.

And with the enormous diversity of insects and arachnids (remember, there are over one million species that we know of), specialists in each group can be few and far between. Having those collections gives those specialists valuable insight into when and where they can find specimens of their group of interest as well as access to them, not to mention all the benefits we've already talked about.

What about photographs and DNA?

Photographs and DNA samples are great tools in studying and monitoring insects, but when it comes to taxonomy (classifying insects), photographs quite often are not sufficient. DNA sequencing is also a much more accessible and commonplace tool nowadays, but it does lack the valuable physical information that you get from an actual specimen.

Can't you just collect bugs that are already dead?

Sometimes you can. That is actually how a good number of specimens for display and artwork are obtained.² But that doesn't work for all insects. Many bugs are tiny and their life cycle is such that under normal circumstances you would never see them. Some methods for capturing such insects involve some sort of trap or bait that you set out for some period of time and which kills the insect during capture. For lots of bugs out there, there simply isn't a better way to find and catch them.

Aren't you worried about overcollecting?

Entomologists do not collect enough insects to where this would be a problem. Let's look at some numbers to back that claim up.

Now this number will vary depending on where you are, but we are going to take the rough number of 4.5 million insects per acre.³ Yes, you heard me. In one acre of land, there can be 4.5 million insects living there. In 2022, the average lot size for a house was 0.3 acres.⁴ Obviously some lots are bigger and some are smaller, but that was the average. That means that if you are living in a house in the suburbs, 1.35 million insects were killed/displaced so that you could have a place to live. Now there are insects that still live on that property, but probably not as many as before, and your house is sitting on top of possibly hundreds of thousands of dead insects.

It takes about 1 acre of land to feed a person for an entire year.⁵ As of 2024, there are about 336 million people living in the United States.⁶ That means about half a billion insects are missing out on that land. Some of them still live there, others were killed by pesticides, and others were displaced (and maybe killed by a car as they were crossing the street).

Speaking of cars, you kill about 16 insects per mile that you drive.⁷ Summed across the whole US, that is hundreds of billions of insects per year that are killed by cars, trucks, buses, trains, etc.

Where am I going with all these numbers? You are unknowingly - both directly and indirectly - already killing insects every single day. As a country, the United States is killing hundreds of billions of insects per year.

So now let's get back to the entomologists. Texas A&M currently has over 3 million specimens in their collection and adds on average 50,000 per year.⁸ The Natural Sciences Institute in Belgium has over 20 million specimens and adds about 100,000 per year.⁹ The University of Kansas has 4.9 million specimens.¹⁰ The Smithsonian insect collection is one of the largest collections in the world with more than 35 million specimens.¹¹ Worldwide, it is estimated that across all entomology collections there are a little more than half a billion preserved specimens.¹² So for the entire history of modern entomology, worldwide there are about half a billion preserved specimens. For comparison, that is the number (not number of species, we're just talking quantities here) of insects that you could find in an area the size of an 18 hole golf course. US drivers alone are killing nearly 400 times that number with their cars just in a single year. My intent isn't to use these numbers as justification for the entomologists, but rather to provide a comparison of how little impact scientific collecting has on insect populations.

Now what?

Those numbers might make it seem dire for bugs, and it is.¹³ But entomologists who are out there killing bugs in the name of science are not causing that decline. In fact, those entomology collections housed in museums are what help us track insect decline.

If you want to learn more about why entomologists kill bugs, Ask an Entomologist has an excellent article about it and I also recommend reading Piotr Naskrecki's response to hate he received regarding a tarantula he collected and killed to add to a museum collection.

I know it can seem counterintuitive that entomologists are killing bugs as they also try to protect and learn about them. Maybe one day we won't need to do so, but for the time being killing bugs is a necessary part of entomology.