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Aeshna umbrosa

What do they look like?

Shadow darners have pale gray-green faces with two antennae, and a strong jaw with teeth. They have 3 large, bright eyes in a triangle that are blue-gray to brown. Surrounding these simple eyes are their more complicated compound eyes, which are bigger and darker. They look different from other dragonflies because they don't have a black stripe across their face. The head is about 7.4 to 8.4 mm long, and they are about 6.5 to 7.8 cm in total. They have two big pairs of wings which are about 8.5 to 10 cm long. (Brooks, 2003; Dunkle, 2000; Johnson, 2011; Manolis, 2003; Montana Natural Heritage Program, 2011; Needham and Westfall, 1955; Novelo-Gutierrez and Tennessen, 2010; Paulson, 2009)

The bodies of shadow darners are strong in the front part of their body, called the thorax, and slender in the back part of their body, called the abdomen. They have have 6 legs and strong claws. Males have yellow-green stripes on the sides of their thorax and blue stripes on top. Their abdomen has pairs of blue spots. Females have the same coloring, but sometimes have green spots. They look a lot like paddle-tailed darners, but have pairs of spots on the bottom of their abdomen that paddle-tailed darners don't. (Brooks, 2003; Dunkle, 2000; Johnson, 2011; Manolis, 2003; Montana Natural Heritage Program, 2011; Needham and Westfall, 1955; Novelo-Gutierrez and Tennessen, 2010; Paulson, 2009)

  • Sexual Dimorphism
  • sexes colored or patterned differently
  • Range length
    6.5 to 7.8 cm
    2.56 to 3.07 in
  • Range wingspan
    8.5 to 10 cm
    3.35 to 3.94 in

Where do they live?

Shadow darners live in all provinces and territories of Canada and in 42 states in the United States. The only states they don't live in are Utah, Arizona, Wyoming, Texas, Louisiana, Florida, Hawaii and Alaska. (Dunkle, 2000; Manolis, 2003; Needham and Westfall, 1955; Northern Prairie Wildlife Research Center, 2006; Paulson, 2009; Pelegrin, 2009)

There are 2 sub-species or shadow darners. Aeshna umbrosa umbrosa live in eastern North America, and Aeshna umbrosa occidentalis live in western North America. (Brooks, 2003; Dunkle, 2000; Johnson, 2011; Manolis, 2003; Montana Natural Heritage Program, 2011; Needham and Westfall, 1955; Novelo-Gutierrez and Tennessen, 2010; Paulson, 2009)

What kind of habitat do they need?

Shadow darners usually live around standing water or in streams with slow-moving water and shadowy places. They live in lakes, ponds, wetland meadows, marshes, and mountain lakes in forests. They are also occasionally found in clearings or along roads, especially when they are hunting. (Brooks, 2003; Dunkle, 2000; Manolis, 2003)

  • Aquatic Biomes
  • lakes and ponds
  • rivers and streams
  • temporary pools

How do they grow?

In cold climates, the eggs go dormant to survive and don't hatch until the spring. If the is water warm enough, the eggs take between 5 days and 2 months to hatch. The eggs hatch into an greenish-brown immature form called a naiad. They are very large, about 3.8 to 4.4 cm long. They are faded in color, have no wings, and live in the water. Before they turn into adults, they climb out of the water and start breathing air. They burst out of their shell by swallowing water. As adults, they can get up to 8.9 cm long. They often get eaten by predators after they first become adults, because their bodies are soft and they can't fly until their new wings harden. This normally happens at night, which helps them avoid predators. Adult dragonflies only live for a few weeks. (Brooks, 2003; Lung and Sommer, 2001; The Brown Family Environmental Center at Kenyon College, 2003)

How do they reproduce?

Male shadow darners do not court females like many species of dragonflies. Females lay eggs in the territory of their mates. Meanwhile, the males guard them to make sure another male doesn't steal her away while she lays her eggs. (Brooks, 2003; Mead, 2003; The Brown Family Environmental Center at Kenyon College, 2003)

Adults are able to fertilize and lay eggs about 2 to 3 weeks after maturing from the larva stage. In harsh climates, this can take longer. They breed from late April through the end of November. This is such a short amount of time that mate as much as they can, about every 1 to 5 days. Females lay eggs in the late afternoon and early evening, usually into plants in the water or in wet, rotting wood. Females cut a hole in the plant with a blade attached their bodies. They lay around 500 eggs at a time, depending on the climate and how much sunlight is available. (Brooks, 2003; Coin, 2004; Corbet, 1999; Iowa Odonata survey, 2005; Lung and Sommer, 2001)

  • How often does reproduction occur?
    Shadow darners breed often as possible (every 1 to 5 days).
  • Breeding season
    Shadow darners breed from late April to November.
  • Range age at sexual or reproductive maturity (female)
    3 to 20 weeks
  • Range age at sexual or reproductive maturity (male)
    3 to 20 weeks

Males pick out a territory for the female to lay eggs where they will have a good chance of surviving. Males also guard the site from other males. Females protect the eggs inside their bodies until they lay them in a nest-like hole they cut in the stem of a plant. (Brooks, 2003; Mead, 2003)

  • Parental Investment
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • male
      • female

How long do they live?

In cold or harsh environments, shadow darners live up to 7 months inside the egg. In warmer places, they hatch after about 1 week. After they hatch, they become a kind of larva called a naiad. They spend most of the time they are alive as naiads. Shadow darners live about 2 weeks as adults. Sometimes they live longer as adults if they can't mate right after they become adults. The longest lifespan of any kind of dragonfly is 77 days. (Brooks, 2003)

  • Range lifespan
    Status: wild
    8 to 26 months
  • Typical lifespan
    Status: wild
    2 to 8 months

How do they behave?

Shadow darners are very active dragonflies. They can fly forwards, sideways and backwards because their wings beat separately from each other in figure eight patterns. In the day and in bad weather, they group together on tree trunks to rest. They can survive in a lot of different temperatures, especially really when it's really cold. When the weather is very hot, they dip themselves into the water to cool down. In cold weather, they bask in the sun on a rock or tree, or beat their wings to warm up. Naiads can swim and move themselves forward by spraying water out of the end of their bodies. Males defend their territories from other males. If an intruder arrives, they approach, threaten, fight, and then chase them. Shadow darners often hunt outside their territory. (Brooks, 2003; Lung and Sommer, 2001; Manolis, 2003)

Home Range

Shadow darner territories are usually a shady area near still or slowly flowing water. The size of the territory depends how many males are in the area. If there are more males around, territories are smaller. (Brooks, 2003)

How do they communicate with each other?

Shadow darners have large, compound eyes which they use to sense movement. They have more groups of light-sensitive cells than any other insect. They can see in color, and see kinds of light that humans can't, like ultraviolet and polarized light. They have 3 more simple eyes between the compound eyes, which they use to see the horizon and navigate while flying. Shadow darners find their mates by recognizing colors, sizes, or shapes. (Brooks, 2003; Frye and Olberg, 1995; Lung and Sommer, 2001)

Shadow darners also communicate by touch. Because their prey move quickly and are easy to see, shadow darners have short antennae. Females reject males they are not interested in by bending the back of their bodies down. Their larvae often communicate by touch because they live in water or swamps. (Brooks, 2003; Frye and Olberg, 1995; Lung and Sommer, 2001)

What do they eat?

Shadow darners eat up to 20% of their body weight every day. They usually hunt at sunset and are most often active in the shade, but will hunt at any elevation and out in the open. They sometimes hunt in a big group with other shadow darners. Shadow darners make a basket with their legs which they use to catch their prey. They eat many kinds of smaller insects, like mosquitoes, midges, and other dragonflies. They avoid eating the wings of their prey, so they pull them off before starting to eat. Naiads eat mostly larvae of insects living in the water. They also eat freshwater shrimp, tadpoles and small fish. (Brooks, 2003; Dunkle, 2000; Kraus, 2010; Lung and Sommer, 2001; Manolis, 2003)

  • Animal Foods
  • amphibians
  • fish
  • insects
  • aquatic crustaceans

What eats them and how do they avoid being eaten?

Adult shadow darners are good at avoiding predators because they can move quickly through the air while flying. Birds like American kestrels, Swainson's hawks, merlins, and purple martins are very good at catching dragonflies. These birds have excellent eyesight and can fly fast enough to catch shadow darners. Shadow darners are also sometimes eaten by large insects like robber flies. Females can be eaten by amphibians like frogs and newts while laying eggs. The immature naiads are camouflaged from predators because they are greenish-brown, but they can be eaten by birds when they come out from their larva skin. (Brooks, 2003; Platt and Harrison, 1995)

  • These animal colors help protect them
  • cryptic

What roles do they have in the ecosystem?

Shadow darners are predators and prey when they are larvae and adults. Female shadow darners lay their eggs inside the stems or leaves of plants to protect them from harsh weather. They get infected with parasites like mites, parasitic worms and protozoans. Parasites attach themselves to shadow darners as they come out of their larva skin. (Brooks, 2003)

Commensal or parasitic species (or larger taxonomic groups) that use this species as a host
  • parasitic worms (Helminthes)
  • protozoans (Protozoa)
  • mites (Acari)

Do they cause problems?

Contrary to what many people believe, shadow darners are not venomous. Dragonflies do carry parasites, so humans could become infected if they ate infected dragonflies, but people in North America don't usually eat dragonflies. (Brooks, 2003)

How do they interact with us?

Like other dragonflies, shadow darners limit the number of insects like mosquitoes that are pests for humans. Sometimes, shadow darner larvae are added to rice fields or water containers to control mosquitoes. Shadow darners also eat other pests and insects that carry disease, like locusts, moths, sandflies and wood-boring beetles. The number of shadow darners can also be a sign of problems with water cleanliness, so shadow darners can be an early warning about the health of an ecosystem. (Brooks, 2003)

Are they endangered?

Shadow darners are not threatened or endangered.

Some more information...

Dragonflies are often used as inspiration in folklore or haiku. They often considered symbols of grace, courage, luck or happiness, and associated with spirits or gods. In Asia, they are believed to be able to combat syphilis, asthma, fever, and other illnesses. (Brooks, 2003)

Contributors

Heather Sanders (author), University of Michigan-Ann Arbor, Renee Mulcrone (editor), Special Projects, Catherine Kent (editor), Special Projects.

References

Brooks, S. 2003. Dragonflies. London: Smithsonian Books.

Coin, P. 2004. "Species Aeshna umbrosa - Shadow Darner" (On-line). Bug Guide. Accessed August 03, 2012 at http://bugguide.net/node/view/6323.

Corbet, P. 1999. Dragonflies: Behavior and ecology of Odonata. Ithaca: Comstock Publishing Associates.

Dunkle, S. 2000. Dragonflies through binoculars: A field guide to dragonflies of North America. Oxford: Oxford University Press.

Frye, M., R. Olberg. 1995. Visual receptive field properties of feature detecting neurons in the dragonfly. Journal of Comparative Physiology A: Neuroethology, Sensory, Neural and Behavioral Physiology, 177: 569-576.

Iowa Odonata survey, 2005. "Shadow darner - Aeshna umbrosa" (On-line). Iowa Odonata Survey. Accessed August 03, 2012 at http://www.iowaodes.com/darners/darn-shad.asp.

Johnson, J. 2011. "Sorting paddle-tailed and shadow darners out-of-hand" (On-line). Northwest Dragonflier. Accessed August 02, 2012 at http://nwdragonflier.blogspot.com/2011/10/sorting-paddle-tailed-and-shadow.html.

Kraus, J. 2010. Diet shift of lentic dragonfly larvae in response to reduced terrestrial prey subsidies. Journal of the North American Benthological Society, 29/2: 602-613.

Lung, M., S. Sommer. 2001. "Aeshnidae: The darners" (On-line). Digital Atlas of Idaho. Accessed February 02, 2012 at http://imnh.isu.edu/digitalatlas/bio/insects/drgnfly/dragfrm.htm.

Manolis, T. 2003. Dragonflies and damselflies of California. Berkeley: University of California Press.

Mead, K. 2003. Dragonflies of the North Woods. Duluth, MN: Kollath-Stensaas Publishing.

Montana Natural Heritage Program, 2011. "Shadow darner - Aeshna umbrosa" (On-line). Montana field guide. Accessed August 02, 2012 at http://fieldguide.mt.gov/detail_IIODO14190.aspx.

Needham, J., M. Westfall. 1955. A manual of the dragonflies of North America (Anisoptera): Including the Greater Antilles and the provinces of the Mexican Border. Berkeley: University of California Press.

Northern Prairie Wildlife Research Center, 2006. "Dragonflies and damselflies (Odonata) of the United States" (On-line). Accessed August 02, 2012 at http://www.npwrc.usgs.gov/resource/distr/insects/dfly/usa/149.htm.

Novelo-Gutierrez, R., K. Tennessen. 2010. Description of the larva of Aeshna persephone Donnelly, 1961 (Odonata: Aeshnidae). Zootaxa, 2484: 61-67.

Paulson, D. 2009. "Aeshna umbrosa" (On-line). The IUCN Red List of Threatened Species(TM). Accessed August 02, 2012 at http://www.iucnredlist.org/apps/redlist/details/165055/0.

Pelegrin, A. 2009. "Aeshna umbrosa Walker, 1908" (On-line). America Dragonfly. Accessed August 02, 2012 at http://america-dragonfly.net/globalResults.php?Species=2986&offset=10.

Platt, A., S. Harrison. 1995. Robber fly and trout predation on adult dragonflies (Anisoptera: Aeshnidae) and first records of Aeshna umbrosa from Wyoming. Entomological News, 106/5: 229-236.

Rudolf, V., J. Armstrong. 2008. Emergent impacts of cannibalism and size refuges in prey on intraguild predation systems. Oecologia, 157: 675-686.

The Brown Family Environmental Center at Kenyon College, 2003. "Odonata: Life cycle" (On-line). Accessed August 03, 2012 at http://bfec.kenyon.edu/dragonfly/lifecycle.htm.

Walker, E. 1953. The Odonata of Canada and Alaska. Toronto: University of Toronto Press.

 
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Sanders, H. 2012. "Aeshna umbrosa" (On-line), Animal Diversity Web. Accessed May 20, 2024 at http://localhost:2015/accounts/Aeshna_umbrosa/

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