Dragonflies, belonging to the order Odonata, are recognized for their striking appearance, featuring a long, slender body, enormous compound eyes, and two pairs of transparent, veined wings. These insects are exceptionally agile fliers, using their aerial prowess to patrol areas around water bodies. While their sudden presence can lead homeowners to seek removal methods, dragonflies are generally considered beneficial insects that play a constructive role in local ecology. This information will guide you through understanding the minimal need for eradication and provide safe, non-lethal methods for managing their population and deterring adults.
Are Dragonflies Really Pests?
The perception of dragonflies as “pests” is largely a misconception driven by their size and speed, as they are non-stinging insects that pose no threat to humans. Their presence is a strong indicator of a healthy local ecosystem, especially concerning the control of nuisance insects. Adult dragonflies are apex aerial predators, relying on their incredible speed and nearly 360-degree vision to hunt prey in flight.
Adult dragonflies consume small, flying arthropods, including mosquitoes, gnats, midges, and flies, which are captured mid-air using their spiny legs. A single adult dragonfly can consume hundreds of these smaller insects daily, providing natural and continuous pest control. Actively trying to eliminate a dragonfly population can inadvertently lead to an increase in the very insects that homeowners find most bothersome, such as biting flies and mosquitoes. The adult stage, which lasts for weeks to a few months, is dedicated almost entirely to hunting and reproduction, making their predatory benefits highly concentrated during the warmer months.
Their ecological value extends beyond the adult stage, as the aquatic nymphs, or naiads, are also voracious predators beneath the water’s surface. These nymphs typically spend a year or more underwater, feeding on aquatic invertebrates, including mosquito larvae.
Managing Larval Habitats
If an overwhelming number of dragonflies is present, it suggests that a local water source is serving as a successful breeding ground. Dragonflies require standing or slow-moving water to lay their eggs, which then hatch into nymphs that can reside underwater for months or even years. Eliminating non-permanent sources of standing water is the most direct method to reduce the number of emerging adults.
This involves regularly emptying collected rainwater from containers:
- Old tires
- Buckets
- Wheelbarrows
- Clogged gutters
For decorative ponds, maintaining clean edges and minimizing underwater foliage is advisable, as nymphs often cling to these plants for shelter. Introducing natural predators, such as certain fish species, can also help control the aquatic insect population, as they will consume dragonfly eggs and nymphs.
Bacillus thuringiensis israelensis (Bti) is a biological control product sometimes used to target mosquito larvae in permanent water. While Bti is specifically toxic to the larvae of certain Diptera insects, including mosquitoes, it is not directly harmful to dragonfly nymphs. However, using Bti can indirectly reduce the dragonfly population by eliminating a major food source like mosquito larvae.
Non-Lethal Adult Deterrence
For homeowners who wish to keep adult dragonflies away from specific areas like a patio or deck, several physical, non-lethal methods are available. Using electric fans to create a steady, disruptive air current is one simple solution. Dragonflies are exceptionally strong fliers, but a concentrated, sustained breeze can interfere with their precise flight patterns and make it difficult for them to hover or perch.
Strategically placed oscillating fans can create a “no-fly zone” around seating areas, forcing the insects to seek calmer air elsewhere. Another method is to reduce the presence of the smaller flying insects that attract dragonflies to the area. Minimizing excessive outdoor lighting at night can limit the number of midges and moths that gather, reducing the available food source.
Physical barriers, such as fine-mesh screens on porches and windows, are highly effective at preventing dragonflies from entering covered spaces. Commercial decoys that mimic a dragonfly can be used to deter other flying pests, such as deer flies and horse flies, which are attracted to the same areas. The absence of its prey will encourage the hunter to move on to more profitable hunting grounds.