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The Ethics, Politics, and Science of Lethal Insect Sampling

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A version of this blog post was written for the Hardy Plant Society of Oregon (HPSO) Quarterly Magazine, and was greatly improved by comments and feedback from the HPSO team of editors.

I had been to my mom’s hometown of Bagamanoc many times, but never before as a budding entomologist. In 1993, I packed my bags with the many tools used to collect and curate insects: glassine envelopes to store and sort butterflies, insect pins and boxes, a pinning block, and nets. Once on the ground in this rural region of the tropics, I set out to catch and kill new specimens for my personal insect collection. My prized find was a large birdwing butterfly, with black and red markings and wingspan of more than 6 inches: Atrophaneura semperi. I nearly vibrated with excitement as I caught her in my net. I carefully pulled her out and held her between my thumb and forefinger, so that I could pinch her thorax and break her flight muscles; a trick that was passed down to me by more experienced entomologists. This would ensure that she could no longer move, an activity that might scrape off scales or tear her wings. Pristine specimens are the standard for insect collections.

A large, red and black Philippine Batwing Butterfly. You can see a hand holding the butterfly's wings.
Philippine Batwing Butterfly. Photo from iNaturalist. © LARKSPUR ALFORQUE, some rights reserved (CC-BY-NC)

By the time I boarded a plane to return home, my prized find had been decimated. Ants had found her, and eaten her abdomen. I was crestfallen and ashamed that I had killed her. Since that time, I largely stopped collecting insects for my personal collection. I limit my collection to two taxa (longhorned beetles and metallic wood boring beetles), to keep from killing and pinning every insect that I see. But I have been involved in the lethal collection of many insect specimens for my work, and it is not without the occasional pangs of guilt.

A recent news story profiled Master Gardener volunteers who had collected 25,000 bees in Pennsylvania to further scientific understanding of wild bee abundance and diversity in the state.1 As the story was shared on social media, the comments and concerns related to lethal sampling accumulated: why was it necessary to kill the bees we are supposed to be helping?

In this article, I briefly examine the science, politics, and ethics of lethal sampling.

The Science

I know of only one study that has directly examined the impact of repeated, lethal sampling on insect communities.2 In this study, the authors sampled wild bees every two weeks throughout a season, or once per season. They found no effect of repeated sampling on any of the response variables they measured, including bee abundance, species richness, or community composition. They suggest that density-dependent competitive release may explain their results: decreased survivorship by some is compensated by increased fecundity from others. In essence, as you remove bees from the community, it reduces the intensity of competition and allows surviving bees to produce more offspring than they would have been able to if they had to compete with other bees for resources.

Lethal sampling has long been the rule in studies of insect biodiversity. In homage to the “lock and key hypothesis,” which suggests that genital morphology acts as a reproductive barrier that ultimately defines a species, identifying an insect to species may mean dissecting out genitalia for microscopic examination. In fact, there is a piece of equipment that some entomologists use, that is designed to inflate and harden insect genitalia, called a phalloblaster or vesica everter. This penis pump for insects cost $2,727 in 1997.

A shift away from lethal sampling has been happening for quite some time, particularly for butterflies and other large insects that can be identified by sight. On iNaturalist, many insects are identified to species by combining advances in machine learning and computer vision with crowd-sourced verifications from the iNaturalist community. The platform has led to the discovery and rediscovery of multiple insect species.3, 4

A few of the 2,691 specimens collected for a recent study of garden bee biodiversity. Photo credit: Gail Langellotto.

The Politics

Insects are generally exempt from regulatory oversight. But recent stories of insect declines and the emergence and growth of the insect farming industry has led at least one law school to teach a course on insect law. Institutional Animal Care and Use Committees (IACUC) govern the ethical care of animals used in research studies, but exempts invertebrates from oversight, except for cephalopods (octopus, squid and cuttlefish).

Few laws govern the collection of insect specimens. However, in the state of Washington, insects are classified as wildlife. Permits are required to collect insects for scientific study. This has complicated the launch of the Washington Bee Atlas, run by the Washington Department of Agriculture, which must secure permits from the Washington Department of Fish and Wildlife for every bee collected.

The Ethics

The cephalopod exemption to IACUC oversight is notable, and is based on the recognition that cephalopods are sentient, self-aware, and capable of feeling or fearing pain. Insects don’t have a brain, per se. Instead, they have three clusters of nerve fibers, which form the supraesophageal ganglion. This fact has sometimes been used to argue that insects can’t feel pain, but reviews of recent studies suggest that there is evidence that some insect adults may feel pain,5 and that some may feel emotional states such as stress.6

Another high-profile study found evidence that bumblebees play.7 Play is classified as an activity that does not result in an obvious reward or adaptive outcome, among other criteria. In this study, researchers documented bumblebees interacting with balls in ways that satisfy the criteria for play. The bees received no reward for this behavior. As in many other animals, younger bees played more often than older bees. If insects are sentient, the field of entomology would undergo a revolution of practice.

Conclusion

Insects are so diverse. Many have yet to be discovered and described, and many others look remarkably similar. The only way to identify most insects to species is to have a physical specimen in hand that you can manipulate and examine under a microscope. And it’s notable that a landmark study of insect declines over 27 years used non-selective Malaise traps to enable the capture and counting of what must be tens of thousands of insects.8 It is extremely difficult to study many questions of insect ecology without lethal sampling.

But scientists are increasingly using and improving nonlethal methods in entomology,9 including the use of DNA barcoding, catch and release, and camera traps. Because the study of insects has largely been exempt from regulatory oversight, most entomologists have yet to reflect on the moral considerations of catching and killing insects. However, as we learn more about insect cognition, the time may be coming to carefully weigh the costs and benefits of lethal collection methods and to invest in technologies that advance the use of non-lethal options.

Aa solar-powered camera trap, to study insect visits to an artificial flower platform. On a single pole is mounted (from top to bottom) a solar panel, camera in protective white housing, and yellow flower platform.
An example of a solar-powered and open sourced camera trap, to study insect visits to an artificial flower platform. Photo by Maximilian Sittinger. (CC-BY-SA-4.0).

1Stimpston, Ashley. 2024. Twenty master gardeners have collected 25,000 bees. Here’s why. The Washington Post (October 24, 2024).

2Gezon, Zachariah J. et al. 2015. The effect of repeated, lethal sampling on wild bee abundance and diversity. Methods in Ecology and Evolution, 6(9): 1044-1054.

3Tugwell, James, Masashi and Gaston, Kevin J. 2024. Sixteen insect species photographed for the first time by citizen scientist. ABC News, Australia (October 19, 2024).

4Mesaglio, Thomas. 2021. First known photographs of living specimens: the power of iNaturalist for recording rare tropical butterflies. Journal of Insect Conservation, 25: 905-911.

5Gibbons, M. et al. 2022. Can insects feel pain? A review of the neural and behavioral evidence. Advances in Insect Physiology, 63: 155-229.

6Lambert, H. et al. 2021. Wouldn’t hurt a fly? A review of insect cognition and sentience in relation to their use as food and feed. Applied Animal Behavior Science, 243: 105432.

7Galpayage Dona, Hiruni Samadi et al. 2022. Do bumblebees play? Animal Behavior, 194: 239-251.

8Hallman, Caspar A. et al. 2017. More than 75 percent decline over 27 years in total flying insect biomass in protected areas. PLOS One, 12(10): e0185809.

9Lovei, Gabor L. and Ferrante, Marco. 2024. The use and prospects of nonlethal methods in entomology. Annual Review of Entomology, 69: 183-198.

Five Scientific Studies that Changed the Way I Think About Gardens, Part 3: Wild Bees > Honey Bees

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This article is the third in a five part series that I am writing for the Hardy Plant Society of Oregon (HPSO) Quarterly Magazine. I am grateful to the team at HPSO for their editorial skills and feedback. Part 1 (overview, and gardens as ‘islands’ in an urban ‘ocean’), and Part 2 (putting a price on nature) of this series can be found in earlier blog posts.

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I distinctly remember the day that I decided I wanted to study wild bees. I was sitting in a darkened auditorium at the American Museum of Natural History in New York City, listening to Claire Kremen deliver the plenary address in a symposium focused on invertebrate conservation.

In her address, Dr. Kremen shared the results of her research on watermelon farms in California’s Central Valley. Like all cucurbits, watermelon requires insect pollination to set fruit. Watermelon, in particular, has a high pollination requirement: it takes at least eight bee visits to deposit the 500-1,000 viable pollen grains needed to set harvestable fruit in seeded watermelons. Seedless watermelons require between 16 and 24 visits by a bee in order to set fruit. Most growers meet the high pollination requirement of melons by renting and placing honey bee hives in fields. Dr. Kremen’s research suggested that a different approach might be possible.

Honey bees are important agricultural pollinators, in large part because they can be moved en mass and placed into farm fields at the exact moment that pollination services are needed.Photo by Isabella Messer.

Dr. Kremen and her colleagues studied three types of watermelon fields that varied in their pest management practices (organic or conventional) and their proximity (near or far) to native habitat in the foothills of the California coast range. These fields were: organic near, organic far, and conventional far. Watermelon fields that used conventional pest management practices and that were located near the foothills were not included in this study because this type of farm did not exist in the region. The team determined the number of pollen grains that different bee species deposited on watermelon, by presenting different bees with a single watermelon blossom that had yet to receive any insect visits. After a blossom was visited by a single bee, the flower was bagged and tagged accordingly, and the number of pollen grains deposited on the stigma by that single bee was counted in the lab. They repeated this process for 13 different bee species.

Next, the team sat in watermelon fields and observed what types of bees visited watermelon blossoms, in different types of farm fields. Watermelon flowers are only receptive to pollination visits for a single day. They recorded the sex and species of each bee visitor to the blossoms. Based upon these species specific counts, combined with the pollen deposition data (above), they were able to assess how much each particular bee species contributed to the production of harvest-ready watermelon.

Dr. Kremen found that pollination surpassed 1,000 pollen grains needed to set harvestable fruit per flower in the organic near fields but not in the organic far or the conventional far field (Fig 1, part A). Furthermore, she found that this outcome could be tied to the greater diversity and abundance of bees in organic near fields, compared to the other two types of fields (Fig 1, part B).

Figure 1. The number of pollen grains deposited on watermelon stigmas (A), and the diversity (orange circles) and abundance (yellow stars) of bees (B) on farms that were classified as organic near (ON), organic far (OF), and conventional far (CF). The number of pollen grains required to set marketable fruit (1000) is noted via a red threshold line in A. (modified from Kremen et al. 2002).

Dr. Kremen also found that, even though no single species of wild bee was as effective as managed honey bees, the collective group of wild bees surpassed the effectiveness of honey bees in organic near fields (Figure 2). Interestingly, honey bees were most effective as crop pollinators in the conventional far fields  and least effective as crop pollinators in the organic near fields. This may be because few other flowers were in bloom in the conventional far fields, so that honey bees concentrated their attention on the crop at hand. In the organic near fields, a greater diversity of flowering plants likely competed for the pollination services of honey bees.

Figure 2. The cumulative contribution of native bees, compared to the contribution of honey bees to the pollination requirement of watermelons on organic near (orange circles), organic far (navy squares), and conventional far (yellow stars) farms (modified from Kremen et al. 2002).

Wild bees were able to fully satisfy the pollination requirements of a crop with an extremely high pollination requirement because broad spectrum insecticides were not used, and the foothills provided year-round and protected habitat for the bees. This story blew my mind!

Prior to that conference, I had never given wild bees much thought. They’re mostly solitary nesters, with small bodies, that only forage for a few days to a few weeks. They tend to be inefficient foragers, particularly when compared to the juggernaut of a honey bee hive. Whereas wild bees are akin to a single vendor on Etsy, honey bees seemed the unbeatable Amazon!

Dr. Kremen’s work showed the potential value that wild bees have to agriculture. And her work was published just prior to the global onset of colony collapse disorder in honey bees in 2006. It set off a worldwide discussion about what to do about honey bee losses. Should scientists put time and effort into saving a single, non-native species (the honey bee), or should we work to conserve or build habitat around farm fields while also reducing insecticide use?

I was incredibly hopeful that the simultaneous threat to honey bees and promise of wild bees might promote heavier investments in agroecology, including the conservation of bee-friendly habitat around farms. During this time period, I was also in the early stages of documenting wild bee biodiversity in community and residential gardens, and I was surprised that abundance and diversity of garden bees was much higher than I had anticipated.

Back in 2004, I started to see gardens, and the abundance and diversity of wild bees that they host, as a potential solution to the problem of colony collapse disorder. Although I continue to be fascinated by the potential role of home and community gardens as a safe haven for bees from agricultural stresses, the urgency of this question has faded. Colony collapse disorder does not currently plague honey bees, due in large part to federal investments in studying, understanding, and mediating the factors that contribute to failing hives. With honey bees doing much better, attention has somewhat faded on the potential role of wild bees as crop pollinators. Still, work in this area continues and may rise to renewed importance, should colony collapse disorder again present a major challenge to United States agriculture.

Wild bees, including this leaf-cutter bee in the genus Stelis are also potentially important crop pollinators. However, many farm practices, such as regular insecticide sprays and mono-cultural cropping systems, make farms inhospitable to wild bees. Photo by Isabella Messer.

Kremen, Williams, Thorp. 2002. Crop pollination from native bees at risk from agricultural intensification. Proc. Natl. Acad. Sci. 99: 16812-26816. DOI: 10.1073/pnas.262413599.