Often seen hovering over ponds, rivers and marshes, damselflies are the flickering jewels of the insect world. But don’t let their shimmering beauty fool you; among insects, they are dangerous predators, with large compound eyes that provide high visual acuity and powerful jaws that crush any prey unlucky enough to get caught by them. These jaws have earned their order the name Odonata, meaning “toothed ones” in Latin.
Damselflies greatly resemble their better known cousins, the dragonflies, and are often mistaken for them. However, damselflies have several important physical characteristics that set them apart: they have straighter wings, slimmer bodies and are generally weaker fliers. The most noticeable difference between the two species, however, is that damselflies rest with their winds outstretched and perpendicular to the body, while dragonflies hold their wings parallel. This difference arises because damselflies lack the proper joints to fold their wings back.
Damselflies mate in summer and fall, not long after emerging from their larvae stage. Female damselflies then lay eggs on vegetation in the water, and larvae emerge soon afterwards. Dsipite being weak swimmers, these larvae are vicious predators, feeding on minnows, tadpoles, and other larvae, which they ambush from underneath plants and grab by their retractable lower jaw. Damselflies remain in the larvae stage anywhere from several months to a few years. While in the larvae stage, damselflies undergo incomplete metamorphosis. Rather than transition from a distinctly identifiable larvae stage, to a pupa and finally an adult, damselfly larvae slowly grow into adult damselflies. Throughout the larvae stage, the damselfly molts several times, emerging as full adults after shedding their skin for the last time.
As adults, damselflies are extremely mobile in the air and are even capable of flying backwards, a feat made possible by two pairs of independent wings. This makes them proficient hunters, capable of grabbing insects such as flies and mosquitoes in mid flight. The damselfly uses its hind legs to seize prey, which are covered in hairs to provide better grip. These are then used to hold the prey as it is eaten by the damselfly.
High mobility and strong jaws are not all that the damselfly has as its disposal to help it obtain food. The damselfly has large compound eyes and can swivel their head on their neck, giving them nearly 360 degree vision. Nearly 80 percent of their brain is devoted to processing visual information. This gives damselflies the ability to spot insects from as far as 40 feet away.
Even though they are near the top of the insect food chain, damselflies are greatly susceptible to the ecological impact of human activity. Damselflies are sensitive to water quality, which makes them especially vulnerable to pesticides and urban development. Currently, two species of Hawaiian damselflies – the earwig Hawaiian damselfly and Pacific Hawaiian damselfly have become endangered due to human development and agricultural practices.
For more information, visit http://insects.tamu.edu/fieldguide/aimg7.html