Like many adults my age, I have fond memories of childhood summer nights spent running around the yard with a jar in hand chasing fireflies, attracted by their awesome glow. My son can certainly find a few fireflies in our backyard, but there seem to be far fewer than I remember. Maybe you have noticed fewer mayflies along your favorite river, or you find you have less bug guts to scrub from your car windshield.
If so, you aren't alone. News reports in recent years have cited anecdotal accounts like these along with research suggesting dramatic insect population declines worldwide. One study showed steep declines in the total weight of insects collected from German nature reserves over a 27-year period. Another study showed a sharp drop in insect biomass in a Puerto Rican rain forest between the 1970s and 2010s. Some media have even put an alarming name on the phenomenon, dubbing it the "Insect Armageddon" or the "Insect Apocalypse."
As an invertebrate ecologist for the Minnesota Biological Survey at the Department of Natural Resources, I find such terminology to be exaggerated, given that it is based on a few geographically restricted studies and that the Puerto Rican study's findings have been disputed. A more recent report in the journal Science looked at 166 insect surveys, primarily in North America and Europe, to arrive at a less alarming, but still concerning, figure: On average, land-dwelling insect populations are declining by 1 percent a year. This report also highlighted the complexity of documenting insect trends in space and time.
In short, some insects are certainly declining, but there is little evidence of apocalyptic worldwide declines. Instead, many studies serve as a call to action to better understand the diversity of insects right here in Minnesota.
As a parent, I worry about what it means for the future if there aren't monarch caterpillars for my child to watch transform into adults. But as someone who studies insects for a living, it's also my job to better understand how we can conserve this incredible diversity. I'm often asked, "How are insects doing in Minnesota?" The answer is complex because insects are incredibly diverse, we know so little about most groups, and there are many ways to measure insect health.
One way we can measure insect health is to consider how many insect species are state or federally listed as threatened or endangered. Such is the case for the Poweshiek skipperling (Oarisma Poweshiek), a once-common, beautiful butterfly with silver pinstripes on its wings. This endangered skipper is now likely extirpated, or presumed gone, from the state, with very few populations remaining in the world.
Another skipper, the threatened Dakota skipper (Hesperia dacotae), is a robust, tawny-orange butterfly with a ton of personality. These insects skip from one perch to the next sipping nectar and searching for mates. What was once a widespread prairie species in Minnesota has been reduced to a single known population. Several other skippers are not federally listed, but we know from statewide searches of populations they seem to be following in the familiar footsteps of the two listed species. Minnesota Biological Survey staff annually conduct surveys for various skipper species and are consistently finding fewer populations each year.
The recently appointed state bee, the rusty patched bumble bee (Bombus affinis), with its orange patch sandwiched between yellow stripes on its abdomen, was once widespread and abundant throughout its range across eastern and central North America. Minnesota is lucky to still maintain populations, albeit fewer than it used to, whereas in other parts of the range the bee is gone or very rare. Other species such as the endangered American burying beetle (Nicrophorus americanus), an orange and black carrion beetle, and the Karner blue butterfly (Lycaeides melissa samuelis) are likely extirpated from Minnesota. The exact causes of these declines are not well known. Instead, it's likely that declines are driven by a variety of factors including the loss, degradation, and fragmentation of habitat; pesticides; invasive species; and global climate change.
Insect Spotters Wanted
Have you spotted an interesting insect? Document your observation on one of these websites. Whenever you contribute a data point, you help advance conservation of insect species. Researchers can use this crowdsourced data to supplement the collective understanding of insect diversity. Bonus: On many of these sites, experts or knowledgeable amateurs will help ID your contributions.
Bumble Bee Watch
The Lost Ladybug Project
Integrated Monarch Monitoring Program
The first step in understanding insects is to document a baseline list of the species present. For most insect groups, we don't have such species lists for Minnesota due to the immense expertise, funding, and time necessary to document insect biodiversity. It's likely that we are losing species before we can even document their existence. There are perhaps tens of thousands of species in the state, but only a fraction of that diversity is documented.
Parasitic wasps, whose young develop on other animals, are perhaps the most diverse group of insects on the planet. We know some things about the ones that parasitize insect pests like emerald ash borer—but we don't even know how many species of parasitic wasps are in Minnesota. Similarly, we are just beginning to document the diversity of well-known groups such as bees thanks to funding from the state's Environment and Natural Resources Trust Fund. To date we have documented about 450 species of bees in Minnesota. To put this number in perspective, this is about the same number of documented bird species found in the state. If even half of the amateur and professional ornithologists started to notice and document insect diversity, we would know far more about insect species in Minnesota—and we'd be closer to the goal of understanding how to conserve them.
Another way we can think about measuring insect health is to count how many individuals are in each population. Some crop pests like soybean aphids are regularly monitored because of their effect on economically important agricultural commodities. Medically important species like mosquitoes are tracked, as are the diseases they transmit. (Mosquito populations are extremely volatile depending on the weather.)
Part of my job at the DNR is to measure population trends of species such as the Dakota skipper. I walk miles through Minnesota prairies, counting all the individuals of this species I see, sometimes hiking for hours before I find one individual perched on a stately coneflower. These counts help biologists understand the density, or how many of a given species are in an area, in order to know how populations change through time.
If I just sat by and watched as the counts declined year after year, all I would be left with would be a rather sad picture of loss. Instead, we in the DNR monitor rare species and work with land managers to devise conservation plans. We conduct what is called adaptive management, a monitoring strategy that helps us learn about the land management factors affecting insect populations. Land managers can then use tools like grazing by cattle or controlled fire to mimic historical disturbances like bison grazing and lightning-caused fires. These disturbances produce flushes of flowers and other resources that many prairie insects rely on for survival.
My hope for the Dakota skipper comes from success stories such as that of the St. Francis' satyr (Neonympha mitchellii francisci) in North Carolina. The St. Francis' satyr was brought back from the brink of extinction through careful understanding of the necessity of periodic habitat disturbance. We know that the Dakota skipper needs disturbance too, but we need to find just the right balance of not enough and not too much. By combining annual population estimates with habitat management information, we use analytical models to understand how a species responds to disturbance. We use these models to make informed decisions about how to best conserve species such as the Dakota skipper. Getting a handle on the population sizes of even a few species of butterflies—let alone all the other insect species—takes a great deal of effort and partnership.
However you measure it, losing insects means more than just losing a few bothersome flies or wasps. Insects have many different functions in the environment, but unless you are paying close attention, their services often go undetected. Without the squash bees (Eucera pruinose) that are so efficient at pollinating those giant zucchinis we plant every summer, our gardens would be less productive. That heirloom tomato plant inherited from your grandpa might not produce fruit if bumble bees weren't around to do their amazing buzz pollination. Many animals, from birds that hunt larvae for their young to black bears that devour ants, rely on large amounts of insects for nourishment. The rainbow scarab (Phanaeus vindex) is a strikingly large red and green beetle that decomposes an amazing amount of animal dung.
Sometimes, insects depend upon other insects for survival. The Karner blue butterfly, for example, depends on ants. Ants are attracted to Karner blue butterfly larvae because they excrete a sugary liquid called honeydew. Without ants tending the larvae, the populations are likely to suffer from increased predation. We don't yet know what kinds of functions are lost when the Karner blue butterfly disappears, but certainly we would lose the beauty they bring to the world.
While there are many apparent losers in the current insect decline, there are also going to be some winners. Some species will fill in the niche space of those that are lost. Insects that can survive in urban areas will benefit from increased urbanization and warmer winters.
For example, the Fiery skipper (Hylephila phyleus) feeds on grass as a larva and flowering plants as an adult. It can't typically withstand our winters and is a migrant in the late summer in Minnesota. However, this species may become more abundant in Minnesota as the climate warms. The common eastern bumble bee (Bombus impatiens) already seems to be increasing in abundance, perhaps due to its ability to live in urban and agricultural environments and to use food resources that are common in gardens and roadsides.
While my role as an ecologist is aimed at preserving Minnesota's insects, I can't do it alone. Anyone can play a role in helping fill the many gaps in our knowledge about the distribution and diversity of insects in Minnesota. Simply getting outside to notice and appreciate the diversity of insects is a great first step. Take a walk through a scientific and natural area, then get down on your hands and knees or use a pair of binoculars and you are guaranteed to find insects. Look closely at a flower and you might find really small insects called thrips that have minute, feathery wings.
Noticing insect signs is a great way to find insects. Look for frass, what scientists call insect poop, or signs of feeding on plants. Turn over a log in the forest and you will surely be rewarded with a variety of insects. Document your findings on nature-observation websites and you become one of the citizen scientists supporting our collective understanding of insect diversity.
The answer to the question of how Minnesota's insects are doing is that some species are certainly declining, some species are doing well, but most species we know nothing about. Our immediate response should be to document the insect diversity in Minnesota so we can begin to know what we might be losing and how to maintain what we have.