We Crush, Poison, and Destroy Insects at Our Own Peril

This past summer, my wife and I ventured to an area near Mount Adams in southwestern Washington state to census bumblebees. We camped there over the weekend as we took part in the Pacific Northwest Bumblebee Atlas survey. Scientists want to fill gaps in their knowledge about the bees. Learning about the relative number of different species, and their floral resources over a broad area, provides invaluable information, particularly when some species are in decline. I was helping to determine where conservation efforts may be needed. Survey participants choose a territory where they capture and photograph bumblebees on two occasions. I still marvel at the variety in the photos we took—bees with coloration incorporating rusty bands of hair, black stubby hairs, white patches, orange bands, and a brilliant, lemon-yellow covering of long hairs. Bumblebees are really quite beautiful when observed more closely.

There is some risk involved, of course. Bumblebees have a painful sting and, unlike the honeybee, with its barbed stinger, the sharp, smooth bumblebee stinger can sting multiple times. Insect stings may serve two purposes. The first is to incapacitate prey. The second is to ward off predators. Bumblebees feed solely on pollen and flower nectar. So they would not sting to subdue prey. A bumblebee nest full of honey and nearly immobile larvae, though, is highly attractive to predators. The bumblebee sting is a weapon used for defense—a mechanism to escape predation from animals that may be 50,000 to 100,000 times their size.¹ And judging by the way most people respond, it works pretty well. The sting of the honeybee has been used as a reference point by sting pain connoisseur, Justin Schmidt. He rates the bumblebee and honeybee stings as a pedestrian 2 on his scale of 1-4.² But that’s a sufficient wallop for people to keep their distance from these bees—and that’s the way the bees like it.

The unparalleled success of insects as a group of organisms results from their ability to escape existential threats. They’re escape artists. They’ve evolved multiple means of eluding the larger animals that endanger them—by stinging, biting, flying, jumping, running, startling, hiding in crevices, and using camouflage as well as chemical defenses. Yet these masters at evading far larger animals face a threat more pernicious than predation today. The resulting decline in the number of insects and in the number of insect species is increasingly well documented. Why should this be alarming? Insects play significant roles as food or in the growth of food for many organisms, including human beings. Insects are also recyclers, decomposing plant matter and animal dung and contributing to the organic content of soils.

It’s not all honey and butterflies in our relationship with insects.

It’s been said that if human beings disappeared, we would not be missed. Insects and other organisms would thrive. Yet we and many other animals would not survive were insects to disappear. The plight of the island marble butterfly (Euchloe ausonides insulanis) and the western bumblebee (Bombus occidentalis) exemplify the multiple stressors on insect survival in the Anthropocene, the proposed name for a new epoch in which human-generated change outstrips the effect of natural forces on the Earth. What responsibilities, if any, do we bear toward these insects? And what can each of us do to stem the tide of global insect decline?

In my recent book, Nature Underfoot, I argue that we crush, poison, and destroy insects and their habitat at our own peril. Yet reasons for acting to prevent insect decline run much deeper than self-interest. Humans cause habitat loss, produce pesticides, and import non-native species. We bear, according to certain strands of philosophical and religious thought, responsibility for the catastrophic losses insects experience today. Some say that insects have moral value since they strive to achieve their ends, just as we and other animals do. Others argue that insects have moral value as a part of God’s creation. Scientists point to the value of insects in global ecosystems, or the value implied by tens or hundreds of thousands of years involved in the evolution of an insect species.

The insect apocalypse has captured headlines, but the situation is more nuanced than that. Scientists find an increase in the overall numbers of arthropods in the Arctic, but a decline in diversity. Certain habitats in the Arctic are also affected more than others.³ In Puerto Rico, insect declines initially attributed to climate change may have resulted instead from hurricanes.⁴ Some insect species have even increased in numbers—mainly those that are tolerant of human activities or that benefit from associating with humans or from climate change.

Despite that, the general trend is negative as climate change, habitat destruction (in the form of deforestation, urbanization, and intensification of agriculture), and pesticides take their toll. These forces are overtaking the insects. They are coming so quickly that even these spectacularly successful evolutionary improvisers do not have time to escape. It’s often difficult for scientists to identify a single contributing factor. A new paper, introducing a special issue on the plight of insects, published in the Proceedings of the National Academy of Sciences, referred to the decline of these tiny creatures as “death by a thousand cuts.”⁵

There is a paucity of long-term records for insect populations. The best historical records are for moths and butterflies in Europe and North America. The story of the island marble butterfly, a grassland species, illustrates the myriad forces arrayed against insects. It was declared endangered in the United States in May of 2020. It is charmingly small—mostly white on the tops of the wings and mottled green, yellow, and white on the undersides. Perhaps its colorful camouflage is a way of escaping predation. This little butterfly was thought to be extinct since 1908, when it was last collected on Gabriola Island, British Columbia. Quite by accident 90 years later, while conducting a survey of butterflies in Puget Sound prairie habitats, a Washington state biologist, John Fleckenstein, collected two of these butterflies on San Juan Island. Neither Fleckenstein, nor his colleague, Ann Potter, could identify the butterflies as they reviewed his collection. So, Potter took the butterflies to a butterfly conference in Corvallis, Oregon, where experts were ecstatic to see the butterfly once thought extinct!⁶

The Lazarus-like return of the island marble butterfly is remarkable, but the pressures that endanger it remain. The prairie habitats where the butterfly is found have been farmed, used for pasture, and developed for housing, destroying much of its original habitat. The butterfly caterpillars feed and develop on plants in the mustard family. The native mustard, Menzies’ pepperweed (Lepidium virginicum var. menziesii), that must have originally supported the butterfly, is often found surrounding lagoons on San Juan Island. These plants and the island marble butterfly are damaged by winter storm surges, which will become more serious as climate change causes sea levels to rise. Fortunately, the butterfly has adapted to feeding on two non-native plants, field mustard (Brassica rapa) and tumble mustard (Sisymbrium altissimum) that grow elsewhere on the island.

We and many animals wouldn’t survive if insects disappeared.

Other invasive species have had a more deleterious effect on the island marble butterfly. The brown garden snail (Cornu aspersum), brought from Europe to the west coast as a source of escargot, competes with the island marble butterfly in consuming field mustard and tumble mustard. The European rabbit (Oryctolagus cuniculus) develops large populations in the San Juan Islands and also feeds on butterfly host plants. Deer, though native in the San Juans, are destructive of prairie habitat. Deer numbers are very high there because their predators, such as wolves, cougars, and bears, were eliminated by European settlers. Deer not only destroy island marble butterfly habitat, but they may ingest eggs and caterpillars in the process. Island marble butterflies also suffer from predation by native spiders and by a European paper wasp (Polistes dominula).⁷

A vigorous and widely distributed population of butterflies could withstand the pressure of predation, but it poses a significant risk for the tiny, localized population of island marble butterflies. Death by a thousand cuts. Habitat destruction, loss of food plants, invasive species, climate change, and predation are primarily human-driven problems. Fortunately, what is believed to be the last island marble butterfly population falls within the boundaries of the San Juan National Historic Park. Here, the park service is actively rearing and releasing butterflies and making a significant effort to preserve their habitat. The island marble butterfly is in a fragile state but hopefully its new endangered status will yield another amazing recovery.

Bumblebees experience similar problems, and the citizen-science survey I described endeavored to generate information about wild bumblebee status—where they occur and what they feed on. They can be found from just east of the Rocky Mountains to the west coast and north from Alaska to Saskatchewan. The tip of the western bumblebee abdomen can be whitish or rusty, yellow hairs may be present or absent above that, and all of these bumblebees have yellow hairs at the front of their thorax behind the head. Bumblebees are important pollinators and, for certain plants, such as tomatoes and blueberries, are better pollinators than honeybees. This led to the domestication of bumblebees for pollination in agriculture, particularly in greenhouses.

In 1992, the U.S. Animal and Plant Health Inspection Service allowed the importation of western bumblebees raised in Europe into the U.S. In 1997, production facilities in California were devastated by a fungal parasite, Nosemi bombi, possibly originating in Europe. At the same time, high levels of N. bombi were found in wild western bumblebee populations, appearing to be related to their significant decline. The coincidental timing of the disease among domestic and wild populations and limited analysis of the parasites indicated that the domestically reared bees infected the wild populations.⁸ If so, it’s another example of how human manipulation of nature may have unforeseen consequences (though some would say the problem was not unforeseen). The commercial production of western bumblebees became financially impractical in the early 2000s.

To conserve insects, there is much we can do in our own yards.

We had hoped to see the western bumblebee in our sampling, because its numbers have dropped precipitously in our area. The western bumblebee was once widely distributed and one of the more common bumblebees found in western North America. More recently, since 1998, western bumblebees have become more difficult to find, particularly west of the Cascade mountains from California to British Columbia. The U.S. Fish and Wildlife Service is currently studying whether to place the western bumblebee on the endangered species list, with a decision planned by 2023.

The western bumblebee is not alone in its misfortune. A 2017 global study found that one-third of the bumblebee species they assessed were in decline.⁹ This habitat loss is driven by agriculture and urbanization, pesticides, climate change, and competition from non-native species. The presence of the bees across their range, based on the modeling of existing data, has been reduced by 93 percent between 1997 and 2018.¹⁰ Scientists will continue to assess the viability of the species as the Fish and Wildlife Service works to determine whether it requires the protection of the Endangered Species Act. Again, death by a thousand cuts is an apt description of the situation facing the western bumblebee. If the N. bombi doesn’t get you, habitat loss will.

Of course, it’s not all honey and butterflies in our relationship with insects. There are occasions when it’s us or them. Insecticide-treated bed nets and spraying long-lasting insecticides on indoor surfaces are some of the best ways to prevent the spread of malaria, which can be debilitating or fatal for many. Destroying the habitat of Anopheles mosquitoes in the southern U.S. helped eliminate malaria there.

But if we agree that we have a responsibility to act to conserve insects, then what can individuals do to aid and abet their escape from human-caused difficulties? There is much we can do in our own yards by constructing a more diverse habitat using native plant species. It is possible to encourage certain species by planting their food plants. There is a program underway in the U.S. to get property owners to plant milkweed (Asclepias syriaca) to support monarch butterflies (Danaus plexippus). Some residents on San Juan Island are also planting the mustard species that are important to the survival of the island marble butterfly. These contributions will help offset some of the degradation of insect habitat. Limiting pesticide use, including insecticides, fungicides, and herbicides would help. I estimate, based on U.S. Environmental Protection Agency data, that around 70 percent of U.S. households use chemical pesticides of one kind or another. We can also limit the use of outside lighting. It makes it difficult for nocturnal flying insects to orient and may kill those that are attracted to the lights.

It would help insects to have more advocates. Speaking up for the conservation of endangered insects is important. Supporting candidates that promise to follow the science and take action against climate change would be another positive step. And, finally, consider joining a citizen-science initiative that provides needed information on insects, not unlike the bumblebee survey I enjoyed. I promise that you’ll be amply rewarded as you explore another, smaller dimension of the natural world.

John Hainze is an entomologist and ethicist. He is an affiliate at the Seattle University Center for Environmental Justice and Sustainability, and an adjunct faculty member at Seattle University.

References

1. Schmidt, J.O. Evolutionary responses of solitary and social hymenoptera to predation by primates and overwhelmingly powerful vertebrate predators. Journal of Human Evolution 71, 12-19 (2014).

2. Schmidt, J.O. Pain and lethality induced by insect stings: An exploratory and correlational study. Toxins 11, 427 (2019).

3. Høye, T.T., et al. Nonlinear trends in abundance and diversity and complex responses to climate change in arctic arthropods. Proceedings of the National Academy of Sciences 118, e2002557117 (2021).

4. Schowalter, T.D., Pandey, M., Presley, S.J., Willig, M.R., & Zimmerman, J.K. Arthropods are not declining but are responsive to disturbance in the Luquillo experimental forest, Puerto Rico. Proceedings of the National Academy of Sciences 118, e2002556117 (2021).

5. Wagner, D.L., Grames, E.M., Forister, M.L., Berenbaum, M.R., & Stopak, D. Insect decline in the anthropocene: Death by a thousand cuts. Proceedings of the National Academy of Sciences 118, e2023989118 (2021).

6. Leinbach Marquis, A. Hiding in plain sight. National Parks 79, 22-23 (2004).

7. U.S. Fish and Wildlife Service. Endangered and threatened wildlife and plants; endangered status for the island marble butterfly and designation of critical habitat. The Federal Register 85, 26786-26820 (2020).

8. Graystock, P., Blane, E.J., McFrederick, Q.S., Goulson, D., & Hughes, W.O.H. Do managed bees drive parasite spread and emergence in wild bees? International Journal of Parasitology: Parasites and Wildlife 5, 64-75 (2016).

9. Arbetman, M.P., Gleiser, G., Morales, C.L., Williams, P., & Aizen, M.A. Global decline of bumblebees is phylogenetically structured and inversely related to species range size and pathogen incidence. Proceedings of the Royal Society B 284 (2017).

10. Graves, T.A., et al. Western  bumblebee: Declines in the continental United States and range-wide information gaps. Ecosphere 11, e03141 (2020).

Lead image: Kriachko Oleksii / Shutterstock

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