North America is home to thousands of species of aquatic insects, and you’re probably familiar with several of them. Anyone who’s spent time near a body of water during the summertime will have seen scores of bugs hanging out on or under the surface of the water, but few will stop to consider the importance of these creatures. In fact, aquatic insects are essential for the healthy functioning of our freshwater ecosystems!
Dragonflies, damselflies, and mayflies are just a few of the aquatic insects most commonly found around the United States, but what else is there to see around our ponds, streams, and rivers?
What are the most common aquatic insects in North America?
There are over 8,600 species of aquatic insects in North America, all of which spend at least a portion of their life in a freshwater environment. These bugs can be found in a variety of habitats, from ponds and water features to streams and rivers. But which aquatic bugs are most common in the USA, and how can you identify them?
Dragonflies and damselflies
Dragonflies and damselflies are some of the most instantly recognizable aquatic insects in North America. Their elongated, brightly colored bodies, bulging eyes, and iridescent wings are a common sight on warm, summer days – but how can you tell a dragonfly from a damselfly?
- Appearance: The main difference in appearance between the dragonfly and the damselfly is in the way they hold their wings. Dragonflies hold their wings wide open, airplane-style, whereas damselflies keep theirs neatly folded over their back when resting.
- Habitat: Dragonflies and damselflies are most commonly found around still or slow-moving water. Look out for them around ponds, lakes, and streams.
The presence of mayflies is a great indicator of good water quality, as the early life stages of these pollution-sensitive insects take place in water. Mayflies are best known for their incredibly short lifespans, with adult insects surviving as little as one day.
- Appearance: These small, winged insects can be recognized from their large eyes, short antennae, and butterfly-like posture. Their most recognizable characteristic, however, is their two long, threadlike tails, which can match or even exceed the length of their bodies.
- Habitat: Mayflies are ubiquitous around North America, and they aren’t fussy about where they set up home. These aquatic pests can be found in a wide variety of still and fast-flowing freshwater habitats, including ponds, lakes, wetlands, rivers, and streams.
Dobsonflies and alderflies
Dobsonflies and alderflies both belong to the order Megaloptera, a name that stems from Ancient Greek and means ‘large wing.’ True to their name, dobsonflies have a wingspan of up to 18 cm, which makes them one of the largest insects found in the United States.
- Appearance: The main difference between dobsonflies and alderflies is their size, as dobsonflies are much bigger. Both insects have long, slender bodies and large, membranous wings but, where dobsonflies have three simple eyes (ocelli) on their heads, alderflies have none.
- Habitat: Dobsonflies and alderflies can be found in a wide range of different freshwater habitats including streams, lakes, ponds, wetlands, and swamps.
Caddisflies are a group of silk-spinning, mothlike insects that spend their larval stages in freshwater habitats. They are common throughout the world, with around 7000 species of Caddisfly known to exist globally.
- Appearance: Caddisfly vary in size but usually range from 3 to 5 mm in length, with wings that fold tent-like over the body. Their long, slender antennae are their most prominent feature, as these are around the same length as their wings.
- Habitat: Lakes, ponds, rivers, and streams may all house Caddisfly, which lives in and around a wide variety of freshwater environments.
What do aquatic insects eat?
Aquatic insects eat a variety of foods, depending on their species. Some eat decaying organic matter or plants, while others are predatory and will dine on other insects.
Shredders have specially adapted mouthparts that allow them to chew away at living or dead plant material. Most of what they eat is decaying plant matter, which falls from trees and shrubs near the waterline.
Scrapers (aka grazers)
Scrapers use their mouthparts to feed on algae, which they scrape off the surface of rocks and other solid objects under the water.
As their name suggests, collectors gather small particles of food from the water using long, fine hairs on their heads and bodies, silk nets, or specially adapted mouthparts to do so. These insects typically feed on detritus (decomposing organic matter) or algae.
Predatory aquatic insects hunt and kill other living organisms. While predatory insects usually eat other invertebrates, some (such as dragonfly nymphs) are big and strong enough to bring down tadpoles and even small fish.
What’s so important about aquatic insects?
The importance of aquatic insects is often underappreciated; however, these minuscule organisms are essential for maintaining a healthy, functioning freshwater ecosystem.
Aquatic insects and the food chain
Many aquatic insect species provide a valuable food source for other freshwater creatures, especially fish.
Therefore, they are vital for maintaining the health and biodiversity of their surrounding ecosystem and, without them, many other aquatic species would die.
Aquatic insects and water filtration
Collectors feed by filtering small food particles out from the water, which purifies it and allows more light to pass through. This means that more sunlight can penetrate to reach plants and algae growing on the bottom.
Aquatic insects and waste removal
Many species of aquatic insect feed on decaying organic matter and algae, preventing a build-up of rotting plant material. Some scrape algae from rocks beneath the water
Aquatic insects can be found throughout the ponds, rivers, streams, wetlands, and marshes of North America. Like terrestrial insects, they come in a variety of shapes and sizes, but one thing they all have in common is the vital role they play in maintaining the balance of their surrounding ecosystem. Aquatic insect larvae are an essential food source for many other organisms and are responsible for much of the waste removal that goes on in freshwater habitats. From water filtration to the processing of decaying organic matter, aquatic insects are more important than you might realize!