Creature Feature: Damselflies

In the animal kingdom, looks can be deceiving. Sometimes the cutest of creatures can be the deadliest of predators: enter, the Damselfly.

Damselflies, or Zygoptera, make up one of two main suborders of the Order Odonata. This order also includes dragonflies, though the term dragonfly is sometimes used to refer to damselflies as well [1]. The order Odonata consists of  more than 6,000 living species, and more than 2,900 of them are damselflies [2]. There are several key features that separate dragonflies from damselflies and will help you to tell them apart at a glance. While dragonfly eyes touch together and make up most of their head, damselflies have a gap between their eyes (this makes damselflies look a lot cuter). The front and back wings of damselflies have the same shape (Zygoptera means “even wings”), whereas in dragonflies, the front and back wings are differently shaped (Anisoptera means “unequal wings”). When at rest, damselflies fold their wings up over their back, whereas dragonflies rest with their wings out to the sides or sometimes angled downwards. Lastly, as mentioned earlier, damselflies are much more slender than dragonflies, making them easier to miss against the branches or reeds they often perch on.

Most damselflies you’ll probably see are in their flying adult stage, but they look much different as larvae. Damselfly larvae are called nymphs, and they are freshwater insects just like their dragonfly cousins. They cannot fly, and instead crawl around on their legs, as their wings are still developing in the “wing sheaths” on their backs. The nymphs of damselflies are easy to distinguish from dragonflies, both due to their slender bodies and their external gills that hang off the back of their body. Damselflies often live in ponds or streams, and they are predators of small invertebrates in those ecosystems. Damselflies catch their prey by extending a labial mask towards their prey to grasp it and then pulling it to their jaws. This process of prey capture is shared with dragonfly nymphs; however, it was first studied and described in damselflies [3]. While Damselfly nymphs are successful predators, they are smaller on average than their dragonfly cousins, and so are preyed upon by fish and larger invertebrates, including dragonflies. When it comes time to emerge from the water and transform into an adult, damselflies often climb atop rocks or up vertical vegetation to prepare for metamorphosis [1].

Damselflies, much like dragonflies, are efficient predators, though they are less studied in that regard than dragonflies. The two most common predation tactics seen in damselflies are sallying and gleaning. Sallying damselflies wait on a perch for prey to fly by, then  dart off to grab it and quickly return to the perch. Sallying is also commonly seen in dragonflies. On the other hand, gleaning damselflies look out for stationary insects on surfaces, and fly over to pluck them off for a nice meal. Gleaning as a tactic is thought to be exclusive to damselflies, as no dragonflies have been consistently observed gleaning [4]. As adult predators, most damselfly species are considered to be generalists (meaning they don’t prefer particular types of prey over others), though each species does tend to prefer a certain size range for their prey. Some of the coolest specialist predators (species that target specific prey) in Odonata are the helicopter damselflies in the tropics. These gleaning damselflies can grow to incredible sizes (the Long-tailed Helicopters can be longer than 8 inches), and they primarily feed on web-building spiders [1]. It’s thought that the colored patches on their wings help distract their spider targets and make them easier to pluck right out of their webs, as those same spiders have been observed avoiding other species, including human observers [1]. 

When mating, Damselflies enter a position called “the wheel,” in which the male grasps the female by the head and the female curls her body towards the male. This odd positioning is due to how the sex organs of damselflies are arranged, but also allows the male to guard the female when she deposits her eggs after mating. The more slender shape of their bodies results in a wheel shape that closely resembles a sideways heart, perhaps making damselflies the more romantic of the bugs in Odonata. When mating is complete, females deposit their eggs in aquatic plant matter or the water itself, often still connected in tandem with the male. Then, the eggs soon hatch and the cycle begins anew.

Painting of Beautiful Demoiselles (Calopteryx virgo) in the wheel position. [Source: Christofer Brothers]

So next time you see a cute, little damselfly perched on a reed or flying through the sky, remember that you’re watching a predator at work, and that looks can be deceiving. 


Christofer Brothers is a graduate student in the Animal Behavior Graduate Group at UC Davis. He is interested in the behavior and biomechanics of flying insects, particularly dragonflies and damselflies. He also has an unhealthy love of puns.


References:

[1] Paulson, D. (2019). Dragonflies and Damselflies-a Natural History. Princeton University Press.

[2] Dijkstra, K-D. B., G. Bechly, S. M. Bybee, R. A. Dow, H. J. Dumont, G. Fleck, R. W. Garrison, M. Hämäläinen, V. J. Kalkman, H. Karube, M. L. May, A. G. Orr, D. R. Paulson, A. C. Rehn, G. Theischinger, J. W. H. Trueman, J. van Tol, N. von Ellenrieder, & J. Ware. 2013. The classification and diversity of dragonflies and damselflies (Odonata). Zootaxa 3703(1): 36-45.

[3] Rowe, R. J. (1994). Predatory behaviour and predatory versatility in young larvae of the dragonfly Xanthocnemis zealandica (Odonata, Coenagrionidae). New Zealand Journal of Zoology, 21(2), 151-166.

[4] Corbet, P. S. (1999). Dragonflies: behaviour and ecology of Odonata. Harley books.

Main image source: Creative Commons license.

[Edited by Alexandra Dwulit]

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