Insects in the lake ecosystem
- 7 minutes ago
- 16 min read
By Mike Scott
Aquatic water insects are some of the least studied elements of the Michigan lake ecosystem, but that doesn’t mean there aren’t ways for local residents to support the insect population.
Unlike aquatic plants, inland lake insects in Michigan are compl,etely native and a valued part of the local ecosystem, according to fisheries and wildlife experts. They tend to congregate around the exterior of a lake, where they are more places to hide in the water bottoms from predators or to feed on plants and algae.
In a healthy Michigan inland lake, especially along plant-filled shorelines, it’s common to find dozens to more than 100 different kinds of aquatic insects and other small organisms, according to the U.S. Geological Survey, with diversity typically dropping off in deeper, open-water areas.
The most diverse types of inland lake insects tend to live around the fringes of aquatic plants, and therefore closer to land, according to Eric Benbow, a professor in aquatic & decomposition ecology within the Department of Entomology at Michigan State University. That is why there is less diversity of insects at the bottom of small, inland lakes further away from shore. The density of insects is also much higher in rivers and streams compared to lakes for multiple reasons, Benbow added.
“You don’t see many (aquatic) insects under water out in the middle of the (lake),” Benbow said. “That’s not where they live.” Airborne insects are a different story, he added.
Invasive insect species are not an issue for Oakland County or other lakes in the state, said Jo Latimore, a senior outreach specialist in the Department of Fisheries and Wildlife at Michigan State University. There are a few invertebrates that can be damaging to a local system in other parts of the country.
“It’s not like airborne insects such as mosquitos which are a nuisance,” Latimore said. “But we don’t have any insects that are a worry that live in the water.”
A higher percentage of aquatic-based insects reside in streams and rivers which tend to have more oxygen that is required by insects. Some of the more common aquatic-based insects travel to lakes from connected streams, rivers and tributaries. The majority of those live around the exterior of a lake by vegetation while some burrow into the base of the lake.
“There are very few insects that are (living) in the middle of a lake under water,” Latimore said. “The diversity of aquatic insects is much higher in rivers and streams.”
Some insects have specialized skills and needs that pre-determines where they live in a waterbody. For example, some types of moths burrow into the stems of water lilies, so they spent their juvenile life within close proximity of those types of aquatic plants, Latimore said.
Fish, amphibians, birds, mammals, other invertebrates, like spiders, and other insects are the secondary production of the food web, said Hillsdale College professor of biology David Houghton. He is known for his work as an aquatic entomologist, specializing in caddisflies and freshwater ecosystems.
Nearly everything eats these types of species either directly or indirectly. Both adults and larvae from these species are important to that process,” Houghton said.
Among the common insects in freshwater bodies around the state are dragon flies, mayflies, caddis flies, various types of true flies and beetles. All have similar benefits as a functional part of ecosystem’s food chain. Some have more predatory tendencies.
Dragonflies are one of those predators that eat smaller insects such as mosquitos and mosquito larvae. They also serve as a desirable prey for fish in the lake, Latimore said. Dragon flies spend time as a juvenile in the water and once they become adults they are able to fly in the air, often remaining near freshwater. Dragonflies are unique in that they can spend up to two years in the juvenile stage before their shorter life span as an adult, Latimore said.
Mayflies are a familiar insect on larger lakes around Michigan. Large groups of mayflies usually emerge from the water as adults simultaneously, which can make them a short-term nuisance to humans aesthetically, although they don’t bite or impact humans directly in other ways. Almost the entire life of a may fly is spent as a juvenile in water where they feed on algae. They burrow into a lake’s under bottom as a juvenile to hide from predators.
An important function of mayflies is that their flutter gills move food and oxygen along a lake, river or stream, which helps to transport items to the organisms that need them. “May flies will swim to the surface of water and shed their juvenile skin when they become adults,” Latimore said. “Their adult stage only lasts a day or two and during that time they are mating machines,” she added with a laugh.
Benbow indicated that non-biting midges, or treeflies, and mayflies are among the most common aquatic insects in Michigan. Mayflies are often referred to as “baited” mayflies by anglers, based on how they are used to attract fish and the fact that mayflies have abundant volumes. Large, soft-bodied burrowing mayflies are often used for fishing bait. They are often referred to informally as “fish flies.”
“They are often found in the bottom sediment areas of many lakes, but often not in open water areas, Benbow said. They are highly nutritious for such fish species as walleye and perch.
Mayflies, or fish flies, effectively consume organic matter, often comprised of dead leaves, plankton, fish skeletons and anything else that will fall toward the bottom of a lake. The ability of insects control the amount of organic matter allows for more effective cycling of oxygen.
That oxygen cycling is a core process that helps to determine how stable a local environment is, based on how oxygen is supplied, distributed, consumed and replenished among different lake zones like the surface, water column and bottom sediments. Most aquatic organism like fish, insect larvae and microbes depend on dissolved oxygen for life, Benbow said.
Furthermore, the carcasses of insects themselves, from flying predators to midges and mayflies become easy-to-find food for fish. This in turn supports anglers as part of a continual cycle.
“For this and other reasons, midges, mayflies and other insects are incredibly important to the fish population and bottom feeders in a lake,” Benbow said. “When these carcasses fall on land, they create huge volumes of biomass that are nutrients for other living beings. This is all important for the infrastructure of the (local) ecosystem.”
Mayflies also can become part of the riparian food web, which refers to the interconnected network of organisms and energy flow that exists in the transition zone between land and water along rivers, streams, lakeshores, and wetlands. This is an ecological distinction from the legal riparian property rights, which govern how private landowners interact with adjacent water bodies. The riparian food web only overlaps geographically.
Male mayflies live up to a two days once they emerge from the water, based on multiple online scientific sources, including the International Fund for Animal Welfare. Female adult mayflies are believed to live for a few minutes.
Caddisflies have a longer lifespan than most other aquatic insects. They can be mistaken for a caterpillar when they are a juvenile. Caddisflies are not predators and like may flies feed on different types of algae. They also serve as food for various types of fish. Caddisflies look like a small moth to the human eye.
“They need to (live) in shallow water where they are closer to food sources,” Latimore said. “They require a significant amount of oxygen and rivers have more (oxygen in the water).”
There are also a wide range of trueflies that inhabit area waterways. Many of these insect species are considered a nuisance to humans, including mosquitoes, deer flies, horse flies and both biting and non-biting midges. As aquatic juvenile insects these species typically are largely hidden from humans. Once they emerge as airborne adults they are considered to be particularly pesky. Their life span as an adult in generally shorter than as a juvenile.
Water striders are another type of true fly commonly seen on Oakland County lakes. They have skinny bodies and are best known for walking on the surface of water. Their bodies are dark brown or black, helping them to blend into the immediate water environment. Water striders are both predators and scavengers, feeding on small inspects like mosquitoes and various dead or injured organisms trapped at or near the water surface.
“For some (true flies), their eggs hatch into larvae that looks like a worm,” Latimore said. “They might end up crawling on a plant for a period of time but every (species) is different.”
Finally, numerous beetle species are considered aquatic insects. The whirligig beetle is notable locally as they are black beetles that faintly resembles a football. These beetles are fast swimmers and often congregate together on a lake surface, swimming for a location together.
“Their eyes are divided in two where they have eyes that look toward the sky for prey and eyes that (simultaneously) look underwater for food,” Latimore said.
Some insects have up to 100 or more species living in Michigan alone, and hundreds more globally, according to Michigan State University Extension. Most mayflies, treeflies, midges, caddisflies and other trueflies tend to emerge from the water as adults in late spring this mid-summer, Benbow said. That means these insects are hatching just as boat and beach season get into full effect in Oakland County. Peak emergence of adult aquatic insects tends to occur from May through July.
Dragonflies, damselflies, different types of beetles, trueflies and more are among the aquatic insects that live much closer to shore. They have more complex habitats in and around both native and invasive plants. Herbivores are comprised of various insects like caterpillars, leaf beetles and different species of aquatic insect larvae that eat plants. Some aquatic insects will also graze bio form off rocks and plants, preventing them from becoming sources of large algae masses.
There are few insects that are truly harmful to the lake ecosystem or the local environment around inland lakes. Many of these insects also control the few pest populations that exist like mosquitoes.
“If you have good, diverse insects that are predators they will consume mosquitos,” Benbow said. “It’s among the various benefits of (inland) lake insects in that they also support the food web, they can help with nutrient carbon cycling and carbon processing.”
The evidence that does exist about insect populations seem to revolve around native vegetation and pollution. As expected, streams and lakes that are closer to urban or highly populated areas tend to be more polluted than those in natural areas. Some macroinvertebrates are more sensitive to pollutants than others, according to Michelle Busch, an aquatic conservation associate with Michigan Natural Features Inventory at Michigan State University Extension.
She said the more sensitive macroinvertebrates to higher levels of pollution in Michigan include the mayflies, caddisflies and stoneflies, aquatic insects frequently found in cold streams and rivers, where their larvae live underwater and serve as important indicators of high water quality.
“Often during biomonitoring, these three groups are typically highlighted, and their proportion is used as a comparison to assess aquatic health,” Busch said. “Ecosystems with higher proportions of (those macroinvertebrates) are in better conditions that those with lower proportions. For reference, some of the more tolerant groups of macroinvertebrates include flies, worms and some snails.
Many juvenile insects in and around Oakland County lakes lack the ability to defend themselves against predators. They can effectively hide in shallow water, but even if consumed by predators like fish and birds, these insects eventually become a part of the natural food chain. It’s a part of the necessary lifecycle.
“Insects are important in many ways (to a lake’s ecosystem) because they are an easy to digest food source,” Latimore said. Each lake’s ecosystem also requires a high volume of these insects so that fish, birds and other non-insects have plenty of prey to needed to stay nourished.
Fish are in part insectivores with that food chain. That includes many sport fish such as trout, bass and bluegills, Busch said. Fly fishers use different types of flies depending on the season and species they are hoping to catch, and the flies often mimic macroinvertebrates.
“Some are made to look like larvae and others are made to look like adults that may have recently emerged or are ovipositing into a body of water,” Busch said.
There are many water birds that will also eat insects, including terns, loons and mergansers, which likely are consuming more insects in the larval stage, she added. However, most aquatic insects will emerge as terrestrial adults and then be consumed by other insectivore birds, bats, and amphibians.
Different insects have different behaviors and occupy different parts of a body of water, such as within sediment, on top of substrate, within the water column and more. “Many of the predators consume different insects and are adapted to hunting down their prey depending on those insect behaviors,” Busch said. “Losing a type of insects due to pollution can lead to a loss of those birds or fish that can no longer effectively feed in a waterbody.”
Interestingly, the threats to freshwater insects in Michigan are largely unknown. According to Latimore, the question hasn’t even been studied much. The population of mayflies largely disappeared from Lake Erie in the 1950s and 1960s. Scientists suggested that water pollution may have been at fault at the time. Mayflies returned to Lake Erie over the years as the pollution seemingly was reduced in the Great Lakes.
Researchers at several universities, including the University of Notre Dame and Virginia Tech, applied radar technology to measure the emergence of mayflies from the Upper Mississippi River and the Western Lake Erie Basin from 2012 to 2019. While the initial study was intended only to quantify mayfly swarms, researchers found a decrease of more than 50 percent in mayfly populations during that time, according to a February 2020 article from the U.S. National Science Foundation (NSF).
The NSF suggested at the time that declines in water quality caused by nutrient and sediment runoff and warmer temperatures may adversely impact mayfly survival.
Latimore agreed that a population decline of native insects in any one area may be a result of multiple reasons, including water quality. Regardless, pollution decreases the levels of oxygen in a waterbody. Still, Latimore admits that there is no conclusive research she is aware of that identifies potential threats to the existence of aquatic insects.
“We don’t know much about how conditions impact the mortality of (insects) or what may cause behavioral changes in them. There really is no new research there I know of,” Latimore said.
It is also unknown how much of an impact, if any, that herbicide runoff in lakes may have on the health of an insect population.
“The lack of mayflies can impact the fish population because fewer (flies) means their food source is gone or reduced,” Latimore said. A complete or majority disappearance of an insect species around a waterbody as happened 60 to 70 years ago is rare, she added.
Insect availability is one of many reasons for a fish population on area inland lakes. Latimore said that Michigan State conducts water studies where students collect samples of content in fish stomachs to track diets. Malnourished fish can be a sign of lack of food sources, although insects are not the only possible prey. If certain species of prey are hard to find, some fish consume prey that is more difficult to digest, such as zebra mussels. That can lead to longer-term health issues in fish populations.
“Either way we tend to spend more time looking at insect populations in streams than lakes, because there are more organisms in streams,” Latimore said.
While lakefront homeowners’ associations and lakefront property owners are faced with challenges regarding how to manage the growth of aquatic plants, there is no need to hire consultants or firms to “manage” an insect population, Latimore said. It might be a different issue if there were invasive aquatic insects, but invasive airborne insects have no adverse impact on a lake’s ecosystem.
“People have strong feelings about aquatic plants and how they impact views and lake quality,” Latimore said. “You don’t see those issues with insects. It’s just a different situation.”
The level of healthiness of insect populations around lakes varies. The best way to determine that level of health is through a bio monitoring program that measures the number and effectiveness of lake insects. These programs are often led and managed by community and environmental based groups and consultants that have the knowledge to effectively measure a lake and categorize them in indices, Benbow said.
“It can be pretty easy to see in some places, but the indices are often measured as good, medium or bad,” Benbow said.
The Michigan Department of Environment, Great Lakes, and Energy (EGLE) has a stream biomonitoring program. Michigan Clean Water Corps, a network of volunteer water-monitoring programs that collect and share data about the health of Michigan’s lakes, rivers and streams, also has stream macroinvertebrate data and collects such environmental data as clarity, chlorophyll, dissolved oxygen and plant information.
Even if a community is mostly composed of more pollution tolerant insects, that community of insects is still doing good things for the ecosystem, Busch said. Many worms and snails are decomposers and work to break down materials to contribute to nutrient cycles. They are an important parts of the food chain as a result. “They decompose materials, consume primary producers, and are a food source for larger animals like fish,” Busch said.
It is generally thought that the more diverse and functional a community of insects are, the healthier the ecosystem is. Busch refers to this as the BEF theory, or the biodiversity-ecosystem function theory. “Every (insect species) has a set of traits or characteristics that relate the organism to the larger ecosystem and its processes,” Busch added. The more functional diversity, the more functional an ecosystem, the more ecosystem services are provided.”
Houghton said researchers at Hillsdale are on the types of detailed metrics that can provide a better sense of the health of an area’s aquatic insects. “A simple sampling for species richness can tell us a lot. We’re also looking at different ecological types of insects is indicative of water quality.”
Houghton published a research article in 2021 that examined how natural and human-driven factors influence aquatic insect communities, focusing on adult caddisflies. Researchers sampled nearly 650 streams across a large region of the north-central U.S. from 1999 through 2019 and evaluated how 52 environmental variables affected species composition and feeding group biomass.
They researchers from that the proportion of intact habitat, especially at the watershed level, was the strongest predictor of insect community health and behavior, with most species and feeding groups declining as habitat degradation increased.
Natural features like stream gradient and width played a larger role in shaping species patterns and diversity in some areas. Overall, while natural factors matter in pristine systems, widespread habitat loss is the dominant force driving declines in caddisfly populations across the region. Habitat loss is often influenced by humans.
“The worst thing you can do is dump chemicals in the water, like from changing your oil or salting your driveway,” Houghton said. “If you live on a lake, don’t turn the entire shoreline into a beach. Aquatic insects need woody debris and rocks to live.”
Houghton published a report on another study in 2023 with other researchers that analyzed caddisfly species richness across the same region of the U.S. Dating to 2025 the researchers have used extensive sampling from nearly 1,000 streams. It identified key environmental and human-related variables influencing species richness, with intact upstream habitat emerging as the most significant factor for about 40 percent of species changes.
The study concluded that natural conditions like elevation and soil characteristics help the caddisfly population, but disturbances such as non-native plants and increased runoff reduce the population. Modeling results showed that habitat loss has severe impacts, with a 50 to 75 percent reduction in intact habitat leading to substantial declines in species richness.
Overall, the findings indicated widespread local extinctions driven primarily by watershed-level habitat disturbance, especially in heavily farmed areas.
“Natural variables like water temperature, latitude, stream width, flow velocity, etc., are less important to caddisfly assemblages than human disturbance,” Houghton said.
If a lake appears to represent a retention pond, which is designed to collect and hold runoff from roads, parking lots, lawns, animal waste and more, it may have a lower than recommended number of lake insects.
“Runoff can impact the number of insects that are in a lake (environment),” Benbow said. “It’s one of many reasons that you want to eliminate fertilizer, road salt and other runoff.”
Environmental consulting firms can conduct biomonitoring programs, though they are often costly and time-consuming. Community-based efforts are another option. These are frequently organized by local residents, lakefront property owners and environmental groups who receive training — or train themselves — to carry out monitoring.
“Once you establish a baseline report, you can monitor annually and compare changes over time,” Benbow said. “Community-based aquatic biomonitoring can be effective with the right knowledge and training.”
There are currently no state requirements for inland lake biomonitoring, Benbow said, though some groups voluntarily report their findings online.
A decline in beneficial native insects can contribute to the spread of not only invasive plants such as Eurasian watermilfoil and Starry stonewort but various types of algae and other invasive species such as red swamp crayfish. These crayfish eat submerged aquatic plants and uproot vegetation through burrowing and foraging activities. The loss of native bed plants removes a habitat for both fish and insects.
There is no single solution to ensuring a healthy population of native insects in an inland lake. However, restoring natural habitat conditions remains one of the most effective strategies.
“You want to do what you can to facilitate their colonization,” Benbow said. “That means addressing the root causes, restoring habitat and reestablishing native plant communities along the shoreline.”
Monitoring invasive plant species can also provide insight into the overall health of an insect population, Benbow said. aquatic insects are tightly tied to vegetation structure, water chemistry, and habitat complexity, he added.
There is evidence that the northern part of Michigan has a healthier population of aquatic insects compared to southern Michigan counties. Outside of cities, most of the Upper Peninsula and the northern Lower Peninsula have predicted species losses from original conditions of less than 10 percent. There’s a line around Bay City and Midland extending a slight southwest angle west to Lake Michigan where species losses quickly increase to around 50 percent or more of the time.
“Every time I analyze my data, with more than 900 sampling sites based on several dozen variables, I find that natural variation is (tied to) the level of human disturbance,” Houghton said. “The amount of habitat upstream of each sampling site that is disturbed by development and agriculture is now the most important force that is structuring caddisfly assemblages.”
There is no magic way to ensure you have the right number of native insects doing the job they ecologically were born to do for an inland lake. The best way to attract more insects is to help restore the lake’s habitat to its natural condition.
“You’re looking to do what you can to facilitate their colonization,” Benbow said. “You want to take steps to mediate the cause of the (reduced population), restore the habitat and reestablish native plant communities as best as possible around lake borders.”
Invasive plant monitoring is one way to get a sense of insect population, Benbow said. Sediment samples are typically collected from lake or river bottoms. Insects may also be collected from river bends or around plants using specialized nets to get a representative sample of insect population.
Perhaps the best advice for lakefront property owners to support a healthy insect population is to maintain a natural habitat near the lake shoreline as much as possible, Latimore said. That includes keeping as many native plants as possible, fallen tree branches and other native items there, even if it means a partially covered view of the lake during warm weather months. Limiting sediment runoff is another recommendation.
“Keep your shoreline as wild as you are comfortable doing,” Latimore said. “It may have a positive influence on the insects you want (in waterways). Every bit of natural shoreline you maintain in theory will help insect species.”
Aquatic insects play a foundational role in the health of inland lakes across Oakland County, acting as both indicators of water quality and essential drivers of the aquatic food web. The native insect species ranging from mayflies to midges help break down organic matter like decaying plants and leaves, recycling nutrients and supporting oxygen balance in lake sediments.
These aquatic insects provide a critical food source for fish, amphibians, and other wildlife, directly supporting recreational fisheries and the broader ecosystem. The diversity and abundance of aquatic macroinvertebrates are widely used to assess ecological health, according to the U.S. Geological Survey.
Above all, lake ecosystems tend to be more resilient, with better water clarity, stronger fish populations, and improved nutrient cycling in lakes where insect populations are diverse and well-balanced. Yet it is still incumbent on humans to do their part.
Busch said it is important for Oakland County property owners to remember is that the creek or ditch that runs by their house eventually will join a stream, which come together into a river, then drains into their favorite lake and has an impact in other connected waterways. In other words, everything in the watershed is connected. Minimizing pollutants from fertilizers to pet waste to household chemicals disposal is essential.
Adding native plants will naturally conserve water and creating rain gardens will help remove excess nutrients from water before it makes its way through the watershed, Busch said.
“Even doing small things, like walking to the store or riding your bike more, help protect watersheds because so many pollutants come from cars,” Busch said. “Aquatic insects are essential parts of our freshwater ecosystems and provide essential services to keep our communities healthy.”