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Wings of wonder: Dragonflies and damselflies

Wings of wonder: Dragonflies and damselflies

Dragonflies are recognized by their long, slender abdomen; large globular eyes, often making up a large portion of the head; short antennae; and long wings. The extant dragonflies are placed in the Odonata order, which is divided into two suborders: the Zygoptera, or damselflies, and the Anisoptera, or true dragonflies. There are about 6400 species of dragonflies and damsels. Dragonflies are generally larger, more robust, and have a stronger flight than damselflies. Damselflies are smaller and have slender and taper wings toward their bases, whereas dragonflies are larger and have hind wings broadening at their bases.

Dragonfly eggs are laid underwater among plants or in silt, which is nicely hidden away from predators. Once hatched, a nymph will spend most of their life—months to years—in this stage before crawling out of the water to turn into a dragonfly. Damselfly larvae can be separated from dragonfly larvae by their caudal lamellae, which are fin-like structures at the end of their abdomen that act as external gills. The adult stage will occur when they have molted, leaving behind an exuvia. Almost all Odonata species need a vertical substrate to emerge from their nymphal life stage into their adult life stage. Adults live for a few weeks to a few months.

Dragonfly as a bioindicator of wetlands

Dragonflies are used as a bioindicator as they are highly sensitive to changes in aquatic habitat. They require clean bodies of water for breeding and feeding, so any alterations in water quality can directly impact their population. Factors like water temperature, acidity, turbidity, or pollution can dramatically upset the survival of the young insect larvae. If dragonflies and damselflies are present in a lake or stream, it indicates good water quality. By studying the presence or absence of different dragonfly species, we can assess the overall health of wetland ecosystems. Further, because their diet consists entirely of insects, dragonfly density is directly proportional to the population of prey. Dragonflies and damselflies are also crucial, as they feed on disease-causing mosquitoes and flies and serve as prey for birds and fish.

Threats and conservation

Nearly 16 percent of the world’s dragonflies and damselflies are at risk of extinction. Primarily due to the destruction and pollution of wetlands. To protect these beautiful, useful insects, protection of the wetland ecosystem (especially in urban areas) is foremost. Avoiding the use of pesticides, which in one way kills its prey, and rainwater carries all the pollutants to wetland, degrading the water quality where nymphs live. Additionally, planting aquatic plants in wetland will help, as it acts as a substrate where female dragonflies can lay eggs and also during the molting period.