Dragonflies belong to the order Odonata. These winged creatures are highly agile fliers, known for their large, multifaceted eyes and long, slender bodies. The immediate answer to whether they are a threat to people is no; dragonflies are harmless to humans. They are formidable aerial predators, but their predatory nature is directed exclusively toward other flying insects, which makes them quite beneficial to humans.
Understanding the Physical Threat to Humans
Despite their intimidating size and appearance, dragonflies pose virtually no physical threat to people. They do not possess a stinger and lack the venom-producing organs associated with stinging insects like bees or wasps, making it impossible for them to sting.
The primary concern people have about dragonflies is their ability to bite, as they have strong mandibles used for capturing and consuming prey in flight. A bite is possible, but it is an extremely rare, purely defensive action that would only occur if a dragonfly were caught and handled roughly. Even in such a defensive scenario, the bite from most species is incapable of breaking human skin. Only the largest species might deliver a nip hard enough to cause mild discomfort or potentially break the skin, but they are not aggressive toward people and will leave an unprovoked human alone.
Ecological Role and Absence of Disease Transmission
Dragonflies play a significant and beneficial role in the environment, primarily acting as natural pest control agents. They are voracious predators, and their diet consists of many insects considered pests by humans, including gnats, flies, and especially mosquitoes. An adult dragonfly can consume hundreds of mosquitoes in a single day, actively reducing the population of biting insects.
Unlike mosquitoes, which act as vectors for pathogens causing illnesses like malaria and West Nile virus, dragonflies do not carry or spread human pathogens. By preying on mosquitoes, dragonflies actively reduce the risk of people contracting mosquito-borne diseases.
Their life cycle also contributes to a healthy ecosystem. The aquatic larval stage, or nymph, lives underwater for months or years. These nymphs also prey on mosquito larvae, further controlling pest populations before they can even take flight. The presence of dragonflies is often an indicator of clean water and a thriving aquatic environment because their nymphs are highly sensitive to pollution.
Identifying Dragonflies Versus Look-Alikes
It is helpful for the public to know how to distinguish true dragonflies from other insects, particularly their close relatives, the damselflies. Dragonflies are generally more robust and have thicker bodies, giving them a stockier appearance. When a dragonfly lands to rest, it holds its two pairs of wings out flat and perpendicular to its body, similar to an airplane.
Damselflies, which are also harmless, have a much more slender and delicate appearance. The easiest visual cue to distinguish them is that damselflies typically fold their wings together over their abdomen when resting. Additionally, dragonflies have large compound eyes that usually meet at the top of their head, while damselfly eyes are clearly separated. Their distinct appearance also differentiates them from stinging insects like wasps, which have an entirely different body shape, usually featuring a narrow “waist” between the thorax and abdomen.