Dragonflies and mayflies are two common and almost famous types of insects, although for different reasons. Dragonflies are easily recognizable by many people as their images have appeared on countless greeting cards, t-shirts, logos, and garden art, thanks to their beautiful, bright colors and distinctive shape. Mayflies are equally famous but among a smaller population of people – namely freshwater fishermen and scientists who study insects. So what are the differences between them?
Both dragonfly and mayfly insects are aquatic as larvae and undergo simple metamorphosis to become winged adults. Adult dragonflies live for several months. Mayflies have two winged stages as adults and live only to mate and lay eggs. They do not eat at all and die within hours of becoming adults.
Beyond both being insects, and thus having exoskeletons, antennae, six legs, and wings, dragonflies and mayflies are far more different than similar. The fact that neither is a “true fly” is only the beginning. Read on to learn more about these two kinds of fascinating insects.
Dragonflies are classified within class Insecta, order Odonata, suborder Anisoptera (to distinguish them within their order from damselflies, which are classified within suborder Zygoptera). Worldwide, there are about 5000 species known, including approximately 300 species north of Mexico (Eaton and Kaufman 2007).
In contrast, mayflies are classified within class Insecta, order Ephemeroptera. Worldwide, there are about 3,000 species known, approximately 600 named species of which are found in North America (Caucci 2011).
Despite their common names, neither dragonflies nor mayflies are “true flies”. True flies are only those insects classified in order Diptera.
Both dragonflies and mayflies are hemimetabolic insects that undergo simple or incomplete metamorphosis. Both insects hatch from eggs, grow through many stages known as instars, and emerge from their final instar in adult form. As larvae, they have obvious heads, thoraxes, and abdomens, along with six jointed legs characteristic of adult insects.
Dragonfly and mayfly larvae hatch from eggs, drop to the substrate of the pond, river, or lake in which they hatch, and then navigate to various micro-habitats, depending on species.
Dragonfly and mayfly nymphs can be “clingers”, “burrowers”, or “sprawlers”. Clingers have strong legs that help them hold onto the substrate and avoid being swept away by water currents. Burrowers dig into the substrate to hide, and sprawlers flatten themselves against the substrate at the bottom of the water column.
Additionally, dragonfly larvae can be “hiders”, which conceal themselves under dead leaves and debris and are often covered in bristles, which catch mud particles to further camouflage them. Mayfly larvae may also be free-swimming or wrigglers, which speak to how they move through their aquatic environment.
Dragonflies and mayflies differ in their approach to finding food, as do the different types of mayflies.
Dragonfly larvae are exclusively predatory, actively hunting and eating other aquatic creatures, while only some genera of mayflies can be considered true predators.
These include mayflies of genus Analetris, which live in sandy areas, and Anepeorus, which live in areas with rocky substrate. Mayflies classified in genera Psuediron and Spinadis feed on the larvae of midges, while those in genus Siphlonurus feed on mosquito larvae (Edmunds et al. 1976).
But except for these predatory genera, most species of mayflies are considered “opportunistic generalists” as larvae. Most are primarily herbivorous, especially of freshwater algae, but will eat whatever else is available, including animal matter. Some are filter or suspension-feeders and can become extremely abundant in water polluted with manure or fertilizers as these encourage algal growth.
That said, both dragonfly and mayfly nymphs are important sources of food for many other animals, especially fish. Dragonflies are also notorious for cannibalizing other dragonfly larvae when the opportunity arises and often attack mayflies as well. Mayflies have far more to fear from dragonflies than vice versa.
The anatomy of both dragonfly and mayfly larvae differ based on their eating behavior.
Both types of insect have mouthparts that consist of a labrum, mandibles, maxillae, hypopharynx, and labium. Dragonflies are unique among insects in that their labiums (roughly analogous to a lower lip) are highly specialized and can be shot forward from the head like a harpoon to attack their prey. Once prey has been captured, the labium is retracted to the head where the larva’s mandibles can chew it.
Mayfly larvae lack this spear-gun-like mouth anatomy; instead, their mouthparts vary depending on the type of mayfly and how each eats.
Burrowing types have tusks on their mandibles for digging. Filter-feeders have fringed setae on their maxillary and labial palps to strain and capture food particles floating in the water. Carnivorous mayflies have sharp mandibles and other species have special stiffened setae on their maxillae that let them scrape algae off rocks. (Thorp and Rogers 2014).
Dragonfly and mayfly larvae also breathe differently underwater. While both rely on dissolved oxygen in the water, dragonfly larvae breathe through their skin and their anuses. They can draw oxygenated water into their abdominal cavity through their anuses and expel de-oxygenated water the same way. Mayfly larvae breathe through seven tracheal gills located on their abdomen; different species have their gills in slightly different places on their abdomens (the locations of the gills vary depending on species (Edmunds et al. 1976).
The adult stage is where the differences between dragonflies and mayflies are most obvious.
Both dragonflies and mayflies have two sets of translucent wings as adults but their shapes differ. Dragonflies have two sets of long, narrow wings which are all roughly the same size and always held out to the side, giving them their distinctive silhouettes; they are unable to fold their wings over their backs. Some species sport spots or patches of color on their wings.
On the other hand, mayflies have large, roughly triangular forewings and much smaller hindwings; on some species, the hind wings are so small as to be almost entirely absent. Their wings are usually entirely clear and mayflies hold their wings folded over their backs when at rest.
Another visible difference between adult dragonflies and adult mayflies are their legs.
Dragonflies’ six legs are strong, grouped together at the front of their thoraxes for perching, and their forelegs are lined with sharp spines that grip their insect prey and prevent escape. Male and female dragonflies have the same type of legs.
In contrast, a mayfly’s legs are weak and sometimes nearly vestigial, with the exception of the forelegs on males, which are elongated to help the males grip the females during mating. The legs on female mayflies are short and around the same length.
The eyes of dragonflies and mayflies are also different. Both dragonflies and mayflies have multi-faceted compound eyes along with simple eyes called ocelli.
But dragonfly eyes are large, bulbous, and either meet or nearly meet along the tops of their heads. Vision is extremely important for dragonflies as they are active predators of other flying insects and have keen abilities to sense motion, color, and shapes.
Unlike dragonflies, whose eye anatomy is the same between the sexes, mayfly eyes are sexually dimorphic, which means they look slightly different depending on whether the mayfly is male or female.
Male mayflies also have large, eyes that may meet on the tops of their heads, although they are never as large and obvious as those of dragonflies. They may be a different color on top – usually orange or red – and the upper eye facets of some species are raised up on stalks. This kind of eye anatomy is called “turbinate” or “semiturbinate” and is seen on some male mayflies, such as the species in genera Baetidae and some Leptophlebiidae. In contrast, female mayfly eyes are small, separated, and all one color.
Both dragonflies and mayflies have long, segmented, cylindrical abdomens tipped with important anatomical structures, including cerci. Females of both insects end in ovipositors, the structure through which eggs are laid but males differ.
Male dragonflies have cerci or “claspers” of various sizes and shapes on the tips of their abdomens, which they use to grip the heads of females during mating.
Mayflies have either two or three “caudal filaments”. Some species have only a pair of cerci, which are long, thin filaments that project from the tips of their abdomens. Unlike the cerci of dragonflies, which are short, mayfly cerci are usually two or more times their body lengths, although length varies by species. Other species have the same paired cerci with an additional filament in between; with the exception of some species in genus Ephemerella, this middle filament is always shorter than the cerci (Edmunds et al. 1976).
Final Instar to Adult Form
Dragonflies and mayflies differ significantly in how they transition from their final larval instar to the adult form. Both dragonflies and mayflies molt by climbing out of the water, splitting their exoskeletons apart, and perching on vegetation until their wings harden.
For dragonflies, the transformation process stops there; they are full adults as soon as they emerge from their underwater larval habitat and undergo their final molt. In contrast, mayflies are unique among insects in that they have two adult stages, a partial sub-adult form known as a “subimago” and a full adult form known as an “imago”.
More commonly known as “duns”, subimago mayflies (or “subimagines”) are the first form assumed after molting after emergence from underwater. Duns look similar to the full adult form except they have shorter cerci and terminal filaments, darker wings, setae along the wing edges that give them a subtle fringed look, and the males have shorter forelegs than seen on the full imagines (Thorp and Rogers 2014).
Many dun mayflies never live long enough to molt the final time into their full imagine stage; these insects simply don’t live long enough even at the best of times, and are eaten by the hundreds by their many predators as soon as they emerge.
Assuming they survive long enough, the duns molt a final time to become full adults, commonly known as “spinners”. Their cerci and males’ forelegs lengthen significantly, their wings strengthen and lighten, and they focus one-hundred percent of their efforts on the final and most important goal in life – reproduction.
Both dragonflies and mayflies reproduce as adults. Male dragonflies actively search for and pursue females, they mate, and the females fly off to lay eggs to ensure the next generation. But dragonflies are relatively long-lived for insects; individual dragonflies can live for several weeks to a couple of months assuming they avoid their many predators such as insectivorous birds and web-building spiders. During this time, dragonflies do more than simply mate. They spend a great deal of time hunting and eating prey.
In contrast, mayflies are famously short-lived. Most species live for only about an average of twenty-four hours (Bauernfeind and Soldan 2012), although a few can live up to three days. The white mayfly (Ephoron album) lives only around ninety minutes and have such short lifespans that the females don’t live long enough to molt into imagines; they mate and lay their eggs as sub-adults (Edmunds 1976).
Adult mayflies have to live fast so have a singular focus; reproduction. Their sole purpose is to mate and lay eggs. Unlike dragonflies, who have robust mouthparts ideal for slicing and biting through their insect prey, mayfly mouthparts are vestigial; they don’t eat at all during their flight stages.
Mayflies are famous for their astonishingly well-synchronized mass emergences during which hundreds and thousands of mayflies climb out of the water, form huge mating swarms above swarm markers such as rocks, bushes, twigs, or trees, mate, lay eggs, and die all at the same time. Mayflies are tempting targets for all manner of predators. The mass emergence of so many individuals at once is thought to be an evolutionary adaptation to overwhelm available predators and ensure that enough mayflies survive to reproduce.
Different species time their mass emergence to different parts of the day so mayflies can begin to swarm anytime of day, from full night to broad daylight. Temperature, the availability of food for the larvae, and light intensity seem to be factors that determine when different mayfly species metamorphose into adults, with temperature likely guiding when the emergence happens and light intensity acting to synchronize the behavior (Bauernfeind and Soldan 2012).
The adults form huge mating swarms thousands or more individuals strong. Different species form different types of swarms, characterized by the relative numbers of males vs. females in the swarm and how the males behave within the swarm.
Some swarms are made up on nearly equal numbers of males and females, while others are made up entirely of males. In the case of all-male swarms, the females dart in from the perimeter, mate, then flee to lay their eggs. Depending on the species, males may hover or fly slowly parallel to the water surface with their bodies vertical or fly in a lilting pattern where they flap their wings to gain altitude then glide down with their wings held at 45 degree angles (Bauernfeind and Soldan 2012).
Dragonflies and mayflies each have their own special niche in our natural world and while they have many similarities, they are entirely different creatures. Mayflies put the full, exuberant abundance of nature on display when they emerge by the thousands over lakes, streams, and rivers, and watching dragonflies zoom through the air like miniature fighter jets is a quiet pleasure of being outside in the summer months. They are both wonders of the natural world and knowing the similarities and differences between them can only add to our joy in their existence.
Related Now I Wonder Posts
For more about dragonflies and other insects in order Odonata, check out these other Now I Wonder posts:
- Is a dragonfly a fly?
- Can dragonflies walk?
- What do dragonflies do at night?
- What is the difference between a dragonfly and a damselfly?
- Dragonflies vs. Butterflies Part 1: First Comes Form
- Dragonflies vs. Butterflies Part 2: Second Comes Function
- Are there different types of dragonflies?
- Dragonflies vs. Horse Flies: Allies vs. Enemies
Bauernfeind, Ernst, and Soldan, Tomas. 2012. The Mayflies of Europe (Ephemeroptera). Boston: BRILL.
Caucci, Al. 2011. Mayfly Guide. New York: Scott & Nix, Inc..
Eaton, Eric R., and Kaufman, Kenn. 2007. Kaufman Field Guide to Insects of North America. Mariner Books. HarperCollins.
Edmunds, George F., Jensen, Steven L, and Berner, Lewis. 1976. Mayflies of North and Central America. Minneapolis: University of Minnesota Press.
Thorp, James H., and Rogers, D. Christopher, eds. 2014. Thorp and Covich’s Freshwater Invertebrates : Ecology and General Biology. Saint Louis: Elsevier Science & Technology.