At first glance, a swarm of dragonflies can be intimidating. They’re fast, brightly colored insects that can congregate by the thousands in an area. Thankfully, these massive swarms are usually not permanent, and smaller ones can be highly beneficial. In most cases, these swarms are migrating or hunting for some kind of prey.
So let’s get to know the common dragonfly a little better and understand what pests might be attracting the swarm to your yard.
What is a Dragonfly?
Dragonflies, or by their scientific name, Anisoptera, are large, predatory flying insects. Some species, like the green darner, are so large they prey on small birds. They belong to the order Odonata, along with the damselfly. They have large, compound eyes, two sets of transparent wings, long bodies, and tooth-like mandibles – these mandibles are where their scientific name, Anisoptera, derives from, meaning “toothed one.” There are over 5,500 dragonflies in North America, with 450 present in the United States and Canada. They can be found on every continent except Antarctica and are most common in southern and coastal states. They’re typically found in bogs, wetlands, and marshes or along riversides, ponds, and lakes.
Dragonflies are a type of hemimetabolous insect, meaning they lack a pupal stage. Instead, dragonfly eggs are laid directly in water, and after about a week, they hatch into nymphs. While in this nymph stage, also referred to as naiads, they will continuously molt (up to 15 times for some species) until they reach maturity. Dragonflies spend most of their lives in their nymph stage, living for two to five years before reaching maturity. When they reach adulthood, they can live for another 5-10 weeks.
Dragonflies are naturally attracted to bodies of standing water. This attraction is due to their need for water in laying eggs and the presence of their primary food source, mosquitoes. Dragonflies prey on mosquitoes as nymphs and adults. While in their naiad form, they will hunt and consume mosquito larvae and eggs, and as adults, they will attack and devour mature, flying mosquitoes. Dragonflies also prey upon fruit flies, gnats, waterbugs, midges, damselflies, and other small insects, most of which congregate around standing water.
What Does a Dragonfly Look Like?
Dragonflies are large insects, ranging from 1 to 4 inches in length, with wings as long as 6 inches. They, like all insects, have a head, thorax, and abdomen with a set of large compound eyes. They possess small antennae and short, thin legs. The most striking feature of the dragonfly is its iridescent and vibrant coloration. They range from deep reds to metallic greens and many other colors. Their wings are most often clear with black veins but can also have a yellow-brown hue.
Dragonfly Vs. Damselfly
Dragonflies are easily confused with the damselfly. They both belong to the same order, Odonata, but are different species. Here are some of the most notable key differences:
- Bodies: Damselflies have smaller, slimmer bodies, with a much thinner thorax.
- Wings: Damselflies rest their wings along with their bodies when not in flight. Dragonflies’ wings always sit horizontally to their bodies. The damselfly’s wings can also be metallic or iridescent in color, while the dragonflies usually are transparent.
- Flight: Damselflies are less powerful fliers than dragonflies.
What Are the Benefits of Dragonflies?
Dragonflies are a form of natural pest control and are considered beneficial insects. Dragonflies don’t damage plants and are not aggressive to people – while they can bite, they will only do so when threatened, and even then, it is not likely to break the skin. Their primary prey is some of the most troublesome pests you can encounter: mosquitoes, ants, termites, gnats, flies, wasps, butterflies, and water bugs.
Why Are Swarms of Dragonflies in My Yard?
There are several reasons dragonflies might swarm in and around an area. According to an aquatic entomologist who runs a blog called The Dragonfly Woman, dragonfly swarms fall into two categories, low altitude and high altitude swarms. Low altitude or static swarms are used for feeding, while high altitude swarms are for migration and breeding.
If you’re experiencing a swarm of dragonflies in your yard, it is likely the former. Migratory swarms only travel specific routes, stopping to rest along the way. Locations that migratory swarms pass through will see thousands, or sometimes millions of dragonflies, for a short time before they move along.
Static swarms, however, are almost always caused by a large influx of prey. These swarms typically occur at dawn or dusk and include thousands of dragonflies, other insects, and even larger animals like birds or bats. Several factors can lead to these massive swarms such as:
- A large group of dragonflies has matured: Dragonfly species lay their eggs in large groups. Since species will breed, grow, and develop at specific times throughout the season, you’ll see large swarms of newly emerging adult dragonflies throughout early spring to late fall, creating sequential waves of dragonflies throughout these warmer seasons. These waves of recently matured dragonflies are not technically swarms, as they are not explicitly congregating to eat. Instead, the number of dragonflies in a given area will increase, making their presence more recognizable.
- Seasonal prey movements: Dragonflies’ prey species will hatch and emerge in specific seasons. Dragonflies will cluster around locations their prey is emerging from, creating swarms. One example mentioned by The Dragonfly Lady is the seasonal emergence of ants and termites. During early spring, ants and termites will emerge and begin to spread, which results in dragonflies converging on their colonies.
- Environmental factors amplify prey: Certain environmental factors can alter and amplify prey species. The most typical instance of this is rainfall inflating mosquito populations. Weather fronts can also trap prey species, moving and depositing them from one location to another. Dragonflies swarm the deposit location once the weather front ends.
What Will Attract Dragonflies to My Yard?
There are several reasons why your yard may attract dragonflies. Most of the time, there is some object within, or some element of, your property attracting their prey. The most common cause of dragonfly swarms for homeowners is standing water. Dragonflies rely on the water for reproduction, and so do almost all of their primary prey organisms. If your house is located next to a large body of standing water, such as a lake or pond, it will attract large amounts of dragonflies. Even smaller bodies of water like a pool, birdbath, or koi pond can be enough to create sizable quantities of mosquitoes and, therefore, dragonflies. Similarly, traps like electric mosquito lamps can draw mosquitoes from the surrounding area. Dragonflies can make the connection between these lamps and their prey species and will be attracted vicariously to these lights.
Besides mosquitoes, other prey species can attract dragonflies, such as ants and termites. If you’re experiencing an ant or termite infestation, this will continuously draw dragonflies to your property. Termites, in particular, can draw in dragonfly swarms as they undergo their own swarming event. If a colony has reached a large enough size during the early summer months, termites will begin to produce and release alates or flying termites. These alates can reproduce and will spread out to create their own colonies. These alate swarms number in the thousands and can attract large numbers of dragonflies.
Certain activities can also stir up or otherwise disturb prey species, attracting a dragonfly swarm. For example, mowing your lawn can stir up colonies of gnats, or cleaning out an old log or debris can stir up different fly species. Dragonflies will then swarm this location, swooping down upon the insects as they are agitated from their resting place.
Another major factor in attracting dragonflies is specific garden decor or plants. Objects like large, flat rocks can attract dragonflies, as they are known to sit and “sun” on them. Certain plants can draw in dragonflies along with other helpful garden insects.
- Fanwort: Fanwort, also known as water shield, is a species of aquatic, flowering plant. Popular in garden ponds and aquariums, dragonflies love to lay their eggs along its stalks.
- Arrowhead: This bright white and yellow perennial is known as the duck potato. Dragonflies like to lay their eggs underneath it, and certain species rest on them when hunting.
- Joe-Pye weed: The old Joe-Pye weed is known for its ease of care, bright purple flowers, and its ability to attract butterflies and dragonflies.
- Black-eyed Susan: This plant is simple to grow and hard to kill. Its bright yellow petals and black-brown center attract butterflies, honeybees, and, of course, dragonflies.
- Water lilies: Water Lily is a general term that describes 58 different species of water-growing, flowering plants. They have large, vibrant single flowers that rest atop wide, waxy leaves. They provide valuable cover for pond-dwelling critters, like koi or dragonfly nymphs.
How Do I Prevent Dragonflies?
While generally beneficial, not all homeowners like the presence of dragonflies. If you want to deter them, your best bet is to get rid of mosquitoes. The most critical step is to avoid having standing bodies of water on your property. If you own birdbaths or ponds, clean them regularly. If you own a pool, ensure that it has a functioning pump and is consistently chlorinated. Here are some further steps you can take to reduce dragonfly attracting pests in your backyard:
- Reduce sprinkler usage: Automatic sprinklers can be a great way to upkeep your lawn. They also can easily result in an overwatered lawn if not set correctly or if a sudden rainstorm hits. Ensure there is enough time between your sprinklers cycle for your yard to dry properly, and if you expect rainfall, turn off your system until your lawn has dried. An overly wet yard will attract pests, including ants, termites, earwigs, and gnats.
- Throw away clutter and debris: Rotting wood, piles of trash, mounds of fertilizer, and other debris is like a siren song for pests. Termites especially love old decaying wood, and their eggs can sit inside large firewood piles. Removing and cleaning backyard and garden clutter is good housekeeping and excellent pest control.
- Keep your grass trim and neat: Many pest species love tall unkempt grass. It provides excellent cover and places to lay their eggs. Proper grass height is also crucial for moisture control, with grass between 3 to 4 inches in height being the optimal size for good water absorption.
Dragonflies are one of the natural world’s best pest control specialists. Their nymphs kill mosquito larvae and eggs, and their adults hunt down wasps and gnats with lethal precision. They also have some of the most complex swarming patterns we have ever seen, with migratory swarms that travel up to 18,000 kilometers to lay eggs. While not all homeowners want these little critters buzzing around, you can’t deny they’re good at what they do.