Dragonflies
Yes. Dragonflies are predators at both stages of life. The aquatic larvae, called naiads or nymphs, live in ponds for months to years and eat mosquito larvae and other small water animals. A 2023 meta-analysis of 31 studies found that one dragonfly or damselfly naiad ate about 40 mosquito larvae a day in test containers. The adults, 1 to 3½ in long, catch mosquitoes, midges and other small flies on the wing. They cannot sting, and only large ones can give a harmless pinch if handled. They are not a mosquito control to rely on: the naiads need a pond for months or years, so they are no help in the bird baths, gutters and rain barrels where many garden mosquitoes breed. Keep them with a pond and no pesticides.
At a glance
- Kind
- Wild — attracted, not bought
- Adult
- 1–3½ in; wings held out flat at rest
- Naiad
- Aquatic; hinged jaw shoots out to grab prey
- Eats
- ~40 mosquito larvae a day per naiad (container tests)
- Larval life
- Usually 1–2 years; some species 5+ years
- Adult life
- Usually 1–2 weeks; sometimes 6–8
How it works
Females lay eggs in or on water, or into plant stems at the water's edge. The larva that hatches, called a naiad or nymph, spends most of the dragonfly's life under water. It lies in wait on the bottom or among plants and shoots out a hinged lower jaw to grab anything small enough: mosquito larvae, other insect larvae, crustaceans, worms, tadpoles and even small fish. Naiads moult many times: 5–14 more times after hatching by the British Dragonfly Society's count, 9–17 in all by UF/IFAS's. Development usually takes one or two years, and some dragonflies spend five years or more under water. When ready, the naiad climbs out of the water up a plant stem and the adult emerges, leaving its empty skin behind.
Adults hunt flying insects in the air, holding their legs in a basket shape that is well suited to catching mosquitoes and other small flies. They live only a week or two in most cases, up to six to eight weeks at most. Dragonflies cannot sting. Missouri's field guide says the larger species can give a pinching bite if handled, but cannot harm people.
The evidence on mosquitoes is strong in containers and thin in gardens. A 2023 meta-analysis of 31 studies, covering 47 dragonfly and damselfly species, found that one naiad ate on average 40 mosquito larvae a day, cutting the larval population by 45% a day, with no difference between Aedes, Anopheles and Culex. Those were container experiments. No source we read measured how far dragonflies lower biting in a backyard.
What it is confused with
Dragonflies are easy to recognise; the useful distinctions are from their close relatives, and between the aquatic larvae.
- Also goodDamselflies — The same order and just as useful, but slimmer and more delicate. Most damselflies hold their wings together over the body at rest (spreadwings are the exception), and their eyes are separated by more than an eye's width. Dragonflies hold their wings out flat, have eyes that touch or nearly touch, and a hindwing broader at the base than the forewing.
- Also goodDamselfly naiads — Slender, with three leaf-like gills forming a tail at the tip of the abdomen. Dragonfly naiads have no tail gills; the gills are inside the rear end, and they can shoot forward by squirting water out of it.
- PestMosquito larvae — Small wriggling larvae ('wrigglers') in still water, with comma-shaped pupae ('tumblers') among them. They are among the things dragonfly naiads eat; see mosquitoes.
How to keep it around
Dragonflies spend most of their lives in water, so the first thing they need is a pond. Drawing on the British Dragonfly Society's advice:
- A garden pond, of any size; the British Dragonfly Society calls garden ponds one of the best ways to support local wildlife
- Plants standing up out of the water at the edges, which naiads climb when they leave the water to emerge as adults
- No pesticides in the garden or near the pond: runoff kills the larvae, and sprays remove the flying insects the adults eat
- Native wildflowers and less frequent mowing, to raise numbers of the small flies adults hunt
- Bear in mind that fish eat dragonfly naiads, as do frogs and waterfowl
Pesticide sensitivity
The British Dragonfly Society says pesticide poisoning directly reduces dragonfly survival, particularly of the larvae, which are exposed when pesticides run off into water. Sprays also remove their insect prey. Open the compatibility matrix →
When to choose something else
Dragonflies are welcome, but they are not a mosquito programme. Look elsewhere when:
- Mosquitoes are breeding in bird baths, gutters or rain barrels — empty and refill bird baths weekly, clear gutters, and screen or seal rain barrels; see mosquitoes
- Standing water has to stay, as in a water garden — treat it with Bti (Mosquito Dunks), which kills only mosquito larvae and those of a few related flies
- People are being bitten now — use a repellent and follow CDC advice; Bti does nothing to adults already flying
Dragonflies by target
What it eats and when it turns up differ by pest. Each page below is the picture for one target.