Creature Feature: Dragonflies and Damselflies

A widow skimmer dragonfly. Photo: D. Huntington, OdontataCentral CC.
A widow skimmer dragonfly. Photo: D. Huntington, OdontataCentral CC.

Dragonflies and damselflies are some of the most captivating and enigmatic of flying insects. With their long transparent wings and bright colors, these voracious predators were some of the first flying insects and have changed very little from ancestors that darted through the air 300 million years ago, long before dinosaurs roamed the Earth.

Dragonflies and damselflies are part of the order Odonata. Worldwide, there are over 6000 species of odonates, with new species continuing to be discovered (in 2016, 60 new species were named in Africa alone). Approximately 450 species are found in the U.S. (316 dragonfly species and 131 damselfly species). The website OdonataCentral.com lists 63 species found in Humboldt County.

Odonates are aquatic insects—reliant on freshwater for reproduction—and are found around rivers, lakes, ponds, streams, and swamps. Depending on the species, their eggs are laid either in water or on vegetation near water, and the nymphs (which molt up to 15 times before becoming an adult) also live and hunt in or near water. Odonate nymphs will eat anything they can grab and hold on to—including small fish.

A green darner dragonfly. Photo: Cletus Lee, Flickr CC.
A green darner dragonfly. Photo: Cletus Lee, Flickr CC.

Adult odonates are agile hunters with unique flight abilities. Because each of their four wings beat independently, they can fly forward, backward, and even hover (including hovering up and down like a helicopter) for short periods. They will eat any insect small enough to catch while in flight. A single dragonfly can eat hundreds of mosquitos per day.

Some species are highly localized, while others range widely. About 50 of the world’s Odonata species have been found to seasonally migrate, like birds do, following weather and rain patterns favorable to their life cycle needs. Some dragonflies even make epic journeys across open ocean, covering distances that dwarf that of Monarch butterflies (well-known for their long, four-generation migrations).

Odonates are bioindicators—meaning that their presence, abundance, and diversity are indicative of high water quality and the health of the surrounding environment. Odonate density and abundance is directly related to the populations of prey species, and also positively correlates to the species richness of vascular plants in the area. So seeing a lot of dragonflies and damselflies is a good sign!

A western red damsel damselfly. Photo: R.A. Behrstock, OdonataCentral-CC.
A western red damsel damselfly. Photo: R.A. Behrstock, OdonataCentral-CC.

Both dragonflies and damselflies have large eyes (covering most of their head); long, thin, segmented bodies; and long, finely-veined,  transparent wings. So how can you tell the difference between dragonflies and damselflies? There are several distinguishing characteristics.

1 – Body size. Dragonflies are typically bulkier and have thicker abdomens than those of damselflies.

2 – Eye size. The extra-large eyes of dragonflies nearly cover their entire head, touching or nearly touching across the top. Damselfly eyes are located more to the sides and distinctly separated on the top.

A comparative illustration of dragonfly and damselfly wings. An upper dragonfly wing is on top with a damselfly wing below. Maxwell Lefroy, Wikimedia Commons, CC.
A comparative illustration of dragonfly and damselfly wings. An upper dragonfly wing is on top with a damselfly wing below. Maxwell Lefroy, Wikimedia Commons, CC.

3 – Wing shape. The wings of damselflies are more or less the same shape, narrowing toward the base. The wings of dragonflies are wider overall, with the upper wings slightly smaller and tapered differently than the lower wings.

4 – Resting wing position. The easiest way to tell the difference between dragonflies and damselflies is to notice the position of their wings when not in flight. A dragonfly’s wings remain outstretched at rest, while the wings of most damselflies are held together, either upright or alongside the body.